RE: Question About Measuring Wall Declination
You can build one of these. https://www.mysundial.ca/sdu/sdu_wall_declinometer.html From: sundial [mailto:sundial-boun...@uni-koeln.de] On Behalf Of Michael Ossipoff Sent: July 1, 2023 1:07 PM To: Jeffery Brewer; sundial list Subject: Re: Question About Measuring Wall Declination I realize that you’ve already gotten good answers, but I’d like to say a few things too. … I’m really late replying, because I’ve been trying to figure out how to word answers to a few long assertion-posts from the usual confused self-sure kids at a philosophical forum. After this time, I’m going to, one way or another, in the forum-options, or my inbox-settings, do a setting that stops topic-announcements from those forums from appearing at my inbox. … First, are you sure that a nail in the wall is the best way? It’s very unlikely to go in perpendicular to the wall. Best would be a block or box that’s reliably rectangular-prism in shape. Lacking that, why not use the short cardboard tube from inside a bathroom-tissue roll? … Assume that the plane of its edge at the ends is perpendicular to its axis & cylindrical-surface. … Stand it on a flat surface, & use a carpenter’s square, a right-triangle drafting square, or a protractor, to mark a vertical line on the tube…or at least the two endpoints of a vertical line. … At the top end of the line, make a small notch, & let that be the shadow-casting point, using the line as the nail. … You’ve got the formula for the declination of a vertical wall, in terms of the measurements of the shadow of a perpendicular object, but you’re interested in the derivation of the solution, & you’ve already gotten good answers about that. But I’d like to make a few comments. … I’m going to refer to the declining-ness of a declining wall, its distance from due-south, as its “facing”, because the word “declination” of course already has a meaning in dialing & astronomy—altitude with respect to the equatorial-plane. … Referring to the spherical coordinate-system whose equatorial-plane is the surface of the declining-wall, I’ll call it the “declining-wall system”. To refer to the spherical coordinate-system whose equatorial plane is the surface of a south-facing wall, I’ll call it the “south-face system”. … This is one of those problems in which, it seems to me, the most computationally-efficient derivation isn’t the most straightforward, obvious, natural easiest one. ...where, in particular, the computationally-efficient derivation uses plane-trigonometry, & the more straightforward easy natural one uses a spherical-coordinate transformation. … Formulas for the length & direction of the nail’s shadow, from the Sun’s position in the coordinate-system with its equator parallel to the wall, can be gotten by coordinate transformations from the Sun’s position in the equatorial co-ordinate-system. … Determine the Sun’s equatorial-coordinates: … The Sun’s hour-angle, its longitude in the equatorial-system, is given by the sundial-time (French hours, equal-hours), the True-Solar Time, gotten from the clock-time by the usual use of the Equation-of-Time & the longitude correction. Hour angle is reckoned clockwise (westward) from the meridian. … The Sun’s declination (altitude in the equatorial-system) for a particular day can be looked up, & interpolated for a particular hour. … It seems to me that the most straightforward solution is to transform the Sun’s equatorial coordinates to the south-face system. … Then transform the Sun’s south-face coordinates to the declining-wall system. … The Sun’s altitude in the declining-wall system gives the length of the shadow, Its longitude in the declining-wall system gives the direction of the shadow on the wall. … You could use the shadow’s length or its direction. The shadow’s length, from the Sun’s altitude in the declining-wall system, has a briefer formula, & the length of the shadow is easier to measure than its direction. …& so I’ll speak of using the length of the shadow. … Resuming: When you’ve transformed the Sun’s south-face coordinates to declining-wall coordinates, the resulting formula for the Sun’s altitude in the declining-wall system will include a variable consisting of the angle between one system’s pole & the other system’s equatorial-plane. (That’s the latitude when you’re converting between the horizontal & equatorial systems, & so I call it the “latitude” for any coordinate transformation. That’s what I mean by “latitude”, in quotes, here) … Solve that formula for the “latitude”. Evaluate the “latitude”. Subtract that from 90 degrees, to get the wall’s facing. …thje amount by which it declines. … This assumes that the wall declines by less than 90 degrees. … Incidentally, this isn’t the only problem in which coordinate-transformations seem more straightforward than the plane-trigonometr
Re: Question About Measuring Wall Declination
I realize that you’ve already gotten good answers, but I’d like to say a few things too. … I’m really late replying, because I’ve been trying to figure out how to word answers to a few long assertion-posts from the usual confused self-sure kids at a philosophical forum. After this time, I’m going to, one way or another, in the forum-options, or my inbox-settings, do a setting that stops topic-announcements from those forums from appearing at my inbox. … First, are you sure that a nail in the wall is the best way? It’s very unlikely to go in perpendicular to the wall. Best would be a block or box that’s reliably rectangular-prism in shape. Lacking that, why not use the short cardboard tube from inside a bathroom-tissue roll? … Assume that the plane of its edge at the ends is perpendicular to its axis & cylindrical-surface. … Stand it on a flat surface, & use a carpenter’s square, a right-triangle drafting square, or a protractor, to mark a vertical line on the tube…or at least the two endpoints of a vertical line. … At the top end of the line, make a small notch, & let that be the shadow-casting point, using the line as the nail. … You’ve got the formula for the declination of a vertical wall, in terms of the measurements of the shadow of a perpendicular object, but you’re interested in the derivation of the solution, & you’ve already gotten good answers about that. But I’d like to make a few comments. … I’m going to refer to the declining-ness of a declining wall, its distance from due-south, as its “facing”, because the word “declination” of course already has a meaning in dialing & astronomy—altitude with respect to the equatorial-plane. … Referring to the spherical coordinate-system whose equatorial-plane is the surface of the declining-wall, I’ll call it the “declining-wall system”. To refer to the spherical coordinate-system whose equatorial plane is the surface of a south-facing wall, I’ll call it the “south-face system”. … This is one of those problems in which, it seems to me, the most computationally-efficient derivation isn’t the most straightforward, obvious, natural easiest one. ...where, in particular, the computationally-efficient derivation uses plane-trigonometry, & the more straightforward easy natural one uses a spherical-coordinate transformation. … Formulas for the length & direction of the nail’s shadow, from the Sun’s position in the coordinate-system with its equator parallel to the wall, can be gotten by coordinate transformations from the Sun’s position in the equatorial co-ordinate-system. … Determine the Sun’s equatorial-coordinates: … The Sun’s hour-angle, its longitude in the equatorial-system, is given by the sundial-time (French hours, equal-hours), the True-Solar Time, gotten from the clock-time by the usual use of the Equation-of-Time & the longitude correction. Hour angle is reckoned clockwise (westward) from the meridian. … The Sun’s declination (altitude in the equatorial-system) for a particular day can be looked up, & interpolated for a particular hour. … It seems to me that the most straightforward solution is to transform the Sun’s equatorial coordinates to the south-face system. … Then transform the Sun’s south-face coordinates to the declining-wall system. … The Sun’s altitude in the declining-wall system gives the length of the shadow, Its longitude in the declining-wall system gives the direction of the shadow on the wall. … You could use the shadow’s length or its direction. The shadow’s length, from the Sun’s altitude in the declining-wall system, has a briefer formula, & the length of the shadow is easier to measure than its direction. …& so I’ll speak of using the length of the shadow. … Resuming: When you’ve transformed the Sun’s south-face coordinates to declining-wall coordinates, the resulting formula for the Sun’s altitude in the declining-wall system will include a variable consisting of the angle between one system’s pole & the other system’s equatorial-plane. (That’s the latitude when you’re converting between the horizontal & equatorial systems, & so I call it the “latitude” for any coordinate transformation. That’s what I mean by “latitude”, in quotes, here) … Solve that formula for the “latitude”. Evaluate the “latitude”. Subtract that from 90 degrees, to get the wall’s facing. …thje amount by which it declines. … This assumes that the wall declines by less than 90 degrees. … Incidentally, this isn’t the only problem in which coordinate-transformations seem more straightforward than the plane-trigonometry solution: … I once noticed that a vertical-declining dial can be marked by plane trigonometry, but spherical coordinate-transformations seem more straightforward. … Likewise, it seems to me that the marking of the declination-lines for a Horizontal-Dial can be done most computationally-efficiently by plane trigonometry at the dial., …but calculating the Sun’s altitude & azimuth for each
Re: Question About Measuring Wall Declination
Hi Jeffery you are actually calculating the horizontal angle indicated as 'angolo' on the diagram below ie. deviation of the Sun from the wall under consideration. Hope this helps, Alexei [image: image.png] On Mon, 26 Jun 2023 at 16:37, Jeffery Brewer wrote: > I'm attempting to measure the declination of a wall using a method > described on this web page of The Sundial Primer > https://www.mysundial.ca/tsp/wall_declination.html (also described in > "Sundials: Their Theory and Construction" by Albert E Waugh Chapter 10). > > Referring to Figure 1 of The Sundial Primer reference, "The direction of > the sun relative to the wall, θ, can be determined as follows: θ = arctan( > AB / Nail Length)°" If I label the ends of the nail with points C and D > (see figure below) then the formula can be understood as θ = arctan( AB / > CD )° > > [image: Figure1Modified.jpg] > > With my very rudimentary understanding of basic trigonometry, I understand > how the formula would work for a simple right triangle existing in a single > plane, but not how it works here. It seems to me that AB lies in an XY > plane parallel to the wall, but CD lies along the Z axis, perpendicular to > the XY plane. The shape described by ABCD is a sort of twisted rectangle > and I don't understand how the formula applies. > > I'm almost certainly thinking about this wrong (it feels like an optical > illusion where I can only see the vase and not the faces). > > [image: image.png] > > If anyone can help me "see the light" I would appreciate it. > > Jeff Brewer > > > > > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Question About Measuring Wall Declination
I'm attempting to measure the declination of a wall using a method described on this web page of The Sundial Primer https://www.mysundial.ca/tsp/wall_declination.html (also described in "Sundials: Their Theory and Construction" by Albert E Waugh Chapter 10). Referring to Figure 1 of The Sundial Primer reference, "The direction of the sun relative to the wall, θ, can be determined as follows: θ = arctan( AB / Nail Length)°" If I label the ends of the nail with points C and D (see figure below) then the formula can be understood as θ = arctan( AB / CD )° [image: Figure1Modified.jpg] With my very rudimentary understanding of basic trigonometry, I understand how the formula would work for a simple right triangle existing in a single plane, but not how it works here. It seems to me that AB lies in an XY plane parallel to the wall, but CD lies along the Z axis, perpendicular to the XY plane. The shape described by ABCD is a sort of twisted rectangle and I don't understand how the formula applies. I'm almost certainly thinking about this wrong (it feels like an optical illusion where I can only see the vase and not the faces). [image: image.png] If anyone can help me "see the light" I would appreciate it. Jeff Brewer --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Wall declination
Hello all, My first post here, another sundial enthusiast. Doing my first sundial on a declining westerly wall. Can you share your tips to measure the wall's declination as accurately as possible? From a sat image I measured 10 degrees tilt. With the nail and board method I got 9.2 degrees as an average of a morning and afternoon measurement. Can I get more accurate? regards Ch. --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Wall declination
Charles, for a simple and effective measure see Wall Declination.pdfhttp://www.precisionsundials.com/wall%20declination.pdf and WallDeclination.exehttp://www.precisionsundials.com/walldeclination.exe. I do not know how its accuracy compares to other methods, but it is an easy method to perform. -Bill Gottesman On Sat, Sep 22, 2012 at 7:36 AM, Charles Beck chforens...@gmail.com wrote: Hello all, My first post here, another sundial enthusiast. Doing my first sundial on a declining westerly wall. Can you share your tips to measure the wall's declination as accurately as possible? From a sat image I measured 10 degrees tilt. With the nail and board method I got 9.2 degrees as an average of a morning and afternoon measurement. Can I get more accurate? regards Ch. --- https://lists.uni-koeln.de/mailman/listinfo/sundial --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Wall declination
A sat image gets you close, the azimuth method of measuring the wall declination has inaccuracies as well, however it is probably better with enough samples. I use the sat image when I feel it is detailed enough for an estimate, I verify it with the azimuth method and if close, then I make a model of the final dial, if that checks out then I am good to go. I also use an astro compass which I like however their acuracy is around 1 degree at best. And of course while a magnetic compass (I use a Brunton) can be corrected for megnetic variation/declination, remember that magnetic deviation occurs with nearby objects. Even clay fired bricks can deflect a magnetic compass by quite a few degrees due to a magnetic alignment being established as the fired bricks cool down. My main spreadsheet illustratingShadows.xls is just one tool, there are many excellent tools on the various sundial web sites to choose from. Simon Simon Wheaton-Smith www.illustratingshadows.com Phoenix, Arizona, W112.1 N33.5 From: Charles Beck chforens...@gmail.com To: sundial@uni-koeln.de Sent: Saturday, September 22, 2012 4:36 AM Subject: Wall declination Hello all, My first post here, another sundial enthusiast. Doing my first sundial on a declining westerly wall. Can you share your tips to measure the wall's declination as accurately as possible? From a sat image I measured 10 degrees tilt. With the nail and board method I got 9.2 degrees as an average of a morning and afternoon measurement. Can I get more accurate? regards Ch. --- https://lists.uni-koeln.de/mailman/listinfo/sundial --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Wall Declination Accuracy and Google Earth
On this list we have had a good discussion on using Google Earth to determine wall declination. Jim Tallman described the simple technique using Google Earth's ruler tool. In Google Earth there is a function that allows you to measure headings and distances. I don't remember what it's called, but it will give you true compass bearing of the line you draw with it. Check out the tools at the top of the GE window. I click on each end of a roof ridge, or the gutter line of a building and then convert the heading to the standard sundial declination convention for whichever side of the building that I need. I use this ruler tool routinely to determine wall declinations of remote sundials. It works well but how accurate is it? Remember the rule of thumb for angle x, measured in radians. For small angles, Angle x = Sin x = Tan x. Whether you measure along the arc, on the perpendicular from the the horizontal or the perpendicular from the hypotenuse, the answers are much the same for small angles. For 1°, x, sin x and tan x are all about 1/57, 2?/360. The error in the perpendicular from a wall displaced by 1° is about 1 in 57. Let's call it 1 in 60. When you place a line on a Google Earth image, along a roof edge or whatever, can you place in within 1 ft in 60? If the picture is clear and taken from directly above, of course you can. Given good pictures, Google Earth can determine wall declinations with an accuracy well better than 1°. This is why I use it routinely. Just remember +/- 1° is about 1 in 60. How does this matter for the lines on a sundial? Where does the shadow hit the wall? Consider the triangle of the real wall, the assumed wall and the error in the base of the perpendicular. That is where the shadow hits the wall. The error in where the shadow falls is generally much less that the difference between the walls. It all depends on the specific geometry. Everything is exaggerated as the solar azimuth approaches the wall declination. Tangents racing to infinity are always a problem. Don't divide by zero! My bottom line is to trust Google Earth. Pictures don't lie. Believe that and you will believe anything! Regards, Roger Bailey Walking Shadow Sundials PS. Wearing another hat, I have used Google Earth images to estimate Iran's progress towards nuclear bomb capability, specifically the route involving the production of heavy water and the construction of heavy water moderated reactors to produce Plutonium. My assessment based on GE images and a specific knowledge of nuclear technology predicts 2017. The U235 route can get them there quicker. Details on request. Google Earth is an amazing resource. Sundials, nuclear holocaust whatever. The Google Earth resource is open and transparent.--- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Azimuth calculation/Wall declination
About 10 years ago I worked out a simple method to measure wall declination using just a carpenter's square and an accurate watch. The methods is described here http://www.precisionsundials.com/wall%20declination.pdf, and a simple windows program that does all the calculations for you is here http://www.precisionsundials.com/walldeclination.exe. When I tested it out many years ago, I believe it gave results repeatable at different times and on different days to a few tenths of a degree. -Bill On 7/31/2011 9:57 AM, Andrew Theokas wrote: Fellow dialists: I am using the following well known formula to calculate the sun’s azimuth for a particular time and location: Azimuth= tan-1 (sin H/(sin φ*cos H – cos φ*tanδ) where H= Sun’s hour angle φ= the latitude - 42.3 degrees δ is the sun’s declination - 18.62 degrees The location is in Boston, USA or 42.3 degrees N and 71.04 degrees west I am using the azimuth-azimuth approach to find the declination of a wall found here: http://www.mysundial.ca/tsp/wall_declination.html the time the measurement was made was 11:18 am (daylight savings time is in effect) I can easily calculate that the azimuth with respect to the wall is 26.8 degrees. Here is the problem: using two other independent methods I find that the wall’s declination is 20 degrees East. So 26.8 degrees – Sun’s Azimuth should equal about twenty degrees. But, using the above equation I cannot get an Azimuth value to work. One place where I might be in error is the value of the Hour angle which I compute to be about –16 degrees. But you can also find the Hour Angle on line here at http://pveducation.org/pvcdrom/properties-of-sunlight/sun-position-calculator Where might I be going wrong? Many thanks for a reply! Andrew Theokas --- https://lists.uni-koeln.de/mailman/listinfo/sundial --- https://lists.uni-koeln.de/mailman/listinfo/sundial
RE: Azimuth calculation/Wall declination
THIS is the kind of thing I have been looking for! The kinds of techniques that make the complex math work simply. Cathedrals were built a thousand years ago by people who had little more literacy than needed to do their jobs. None of them knew what a sine or cosine or tangent was. They knew how ratios worked and they knew the practicalities of geometry. Thanks for the great tool. As it happens, I need to measure the declination of a wall and this helps a lot! Karon Adams Accredited Jewelry Professional (GIA) You can send a free Rosary to a soldier! www.facebook.com/MilitaryRosary www.YellowRibbonRosaries.com From: sundial-boun...@uni-koeln.de [mailto:sundial-boun...@uni-koeln.de] On Behalf Of Bill Gottesman Sent: Monday, August 01, 2011 10:55 AM To: sundial@uni-koeln.de Subject: Re: Azimuth calculation/Wall declination About 10 years ago I worked out a simple method to measure wall declination using just a carpenter's square and an accurate watch. The methods is described here http://www.precisionsundials.com/wall%20declination.pdf, and a simple windows program that does all the calculations for you is here http://www.precisionsundials.com/walldeclination.exe. When I tested it out many years ago, I believe it gave results repeatable at different times and on different days to a few tenths of a degree. -Bill On 7/31/2011 9:57 AM, Andrew Theokas wrote: Fellow dialists: I am using the following well known formula to calculate the sun’s azimuth for a particular time and location: Azimuth= tan-1(sin H/(sin φ*cos H – cos φ*tanδ) where H= Sun’s hour angle φ= the latitude - 42.3 degrees δ is the sun’s declination - 18.62 degrees The location is in Boston, USA or 42.3 degrees N and 71.04 degrees west I am using the azimuth-azimuth approach to find the declination of a wall found here: http://www.mysundial.ca/tsp/wall_declination.html the time the measurement was made was 11:18 am (daylight savings time is in effect) I can easily calculate that the azimuth with respect to the wall is 26.8 degrees. Here is the problem: using two other independent methods I find that the wall’s declination is 20 degrees East. So 26.8 degrees – Sun’s Azimuth should equal about twenty degrees. But, using the above equation I cannot get an Azimuth value to work. One place where I might be in error is the value of the Hour angle which I compute to be about –16 degrees. But you can also find the Hour Angle on line here at http://pveducation.org/pvcdrom/properties-of-sunlight/sun-position-calculator Where might I be going wrong? Many thanks for a reply! Andrew Theokas --- https://lists.uni-koeln.de/mailman/listinfo/sundial --- https://lists.uni-koeln.de/mailman/listinfo/sundial
R: RE: Azimuth calculation/Wall declination
May I suggest you to have a look at Orologi Solari ?
It includes two different tools for wall declination measurement.
It could maybe help you.
Greetings.
Gian
http://digilander.libero.it/orologi.solari
Messaggio originale
Da: ka...@karonadams.com
Data: 01/08/2011 17.36
A: Bill Gottesmanbillgottes...@comcast.net, sundial@uni-koeln.de
Ogg: RE: Azimuth calculation/Wall declination
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--
THIS is the kind of thing I have been looking for! The kinds of techniques that
make the complex math work simply.
Cathedrals were built a thousand years ago by people who had little more
literacy than needed to do their jobs. None of them knew what a sine or cosine
or tangent was. They knew how ratios worked and they knew the practicalities of
geometry.
Thanks for the great tool. As it happens, I need to measure the declination of
a wall and this helps a lot!
Karon Adams
Accredited Jewelry Professional (GIA)
You can send a free Rosary to a soldier!
www.facebook.com/MilitaryRosary
www.YellowRibbonRosaries.com
From: sundial-boun...@uni-koeln.de [mailto:sundial-boun...@uni-koeln.de] On
Behalf Of Bill Gottesman
Sent: Monday, August 01, 2011 10:55 AM
To: sundial@uni-koeln.de
Subject: Re: Azimuth calculation/Wall declination
About 10 years ago I worked out a simple method to measure wall declination
using just a carpenter's square and an accurate watch. The methods is
described here http://www.precisionsundials.com/wall%20declination.pdf, and a
simple windows program that does all the calculations for you is here
http://www.precisionsundials.com/walldeclination.exe. When I tested it out
many years ago, I believe it gave results repeatable at different times and on
different days to a few tenths of a degree.
-Bill
On 7/31/2011
Re: Wall declination using google earth
This topic brings up another question - what is the allowance in wall declination measurement which would go unnoticed? In my opinion an error of ±1 degree will not affect any but the largest sundials (and that is mostly only in the early morning and late afternoon hours). --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Wall declination using google earth
Dear Roger, Damia and all, Instead of fiddling with the display settings of the monitor, I use the Pen Tool of my image processing program, Paint Shop Pro, to measure wall declination. I guess other programs have a similar tool. When drawing a straight line over a sharp picture element parallel to the wall (roof ridge, roof edge, street side,...), the status bar shows the direction in 1 decimal. I assume that it is the arc-tangent of the x and y displacements in pixels. With a good quality of the satellite image, the accuracy is about 0.5°. An assumption for this method is, of course, that the x and y pixel distances of the satellite image are equal. Best regards, Frans Maes Roger Bailey wrote: I routinely use Google Earth to determine wall declination. Depending on the quality of the picture, resolution to within one degree can be achieved. The default orientation for Google Earth is straight north up for the center of the starting image. I have a flat screen with vertical sides and horizontal top and bottom that are useful reference lines. Check your screen settings. On most displays these days, x and y are not equal. I had to choose a display settings to match the dimensions of the monitor. There are examples of wall declination using Google Earth in some of the presentations on my website. Timelines #5 may be the most useful. Regards, Roger Bailey Walking Shadow Designs www.walkingshadow.info -- From: Damia Soler Estrela l...@damia.net Sent: Monday, June 08, 2009 5:53 AM To: Sundial List sundial@uni-koeln.de Subject: Wall declination using google earth Hello: You are talking about physical declinometers in order to know the wall declinations, I think that is the most acurrate method, but I have been using google earth, you can see the wall of the buildind or the aligned street, and could calculate the declination from North? (You have a rule to measure the x and y axis, or read the coordinates). What do you think about the accuracy of this method? Do you have any information about the accuraccy of google earth in order to measure declination? Best regards Damià --- https://lists.uni-koeln.de/mailman/listinfo/sundial No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.339 / Virus Database: 270.12.55/2160 - Release Date: 06/07/09 05:53:00 --- https://lists.uni-koeln.de/mailman/listinfo/sundial --- https://lists.uni-koeln.de/mailman/listinfo/sundial
RE: Wall declination using google earth
I do the same thing, but I use the line tool in Delta Cad. I import the Google Earth photo into Delta Cad, then I draw a red line over the wall or roofline. Then using edit tab for the line, Deta Cad tells me the exact angle of the line. -Original Message- From: sundial-boun...@uni-koeln.de [mailto:sundial-boun...@uni-koeln.de] On Behalf Of Frans W. Maes Sent: Tuesday, June 16, 2009 1:14 PM To: Roger Bailey Cc: Sundial List Subject: Re: Wall declination using google earth Dear Roger, Damia and all, Instead of fiddling with the display settings of the monitor, I use the Pen Tool of my image processing program, Paint Shop Pro, to measure wall declination. I guess other programs have a similar tool. When drawing a straight line over a sharp picture element parallel to the wall (roof ridge, roof edge, street side,...), the status bar shows the direction in 1 decimal. I assume that it is the arc-tangent of the x and y displacements in pixels. With a good quality of the satellite image, the accuracy is about 0.5°. An assumption for this method is, of course, that the x and y pixel distances of the satellite image are equal. Best regards, Frans Maes Roger Bailey wrote: I routinely use Google Earth to determine wall declination. Depending on the quality of the picture, resolution to within one degree can be achieved. The default orientation for Google Earth is straight north up for the center of the starting image. I have a flat screen with vertical sides and horizontal top and bottom that are useful reference lines. Check your screen settings. On most displays these days, x and y are not equal. I had to choose a display settings to match the dimensions of the monitor. There are examples of wall declination using Google Earth in some of the presentations on my website. Timelines #5 may be the most useful. Regards, Roger Bailey Walking Shadow Designs www.walkingshadow.info -- From: Damia Soler Estrela l...@damia.net Sent: Monday, June 08, 2009 5:53 AM To: Sundial List sundial@uni-koeln.de Subject: Wall declination using google earth Hello: You are talking about physical declinometers in order to know the wall declinations, I think that is the most acurrate method, but I have been using google earth, you can see the wall of the buildind or the aligned street, and could calculate the declination from North? (You have a rule to measure the x and y axis, or read the coordinates). What do you think about the accuracy of this method? Do you have any information about the accuraccy of google earth in order to measure declination? Best regards Damià --- https://lists.uni-koeln.de/mailman/listinfo/sundial No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.339 / Virus Database: 270.12.55/2160 - Release Date: 06/07/09 05:53:00 --- https://lists.uni-koeln.de/mailman/listinfo/sundial --- https://lists.uni-koeln.de/mailman/listinfo/sundial --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Wall declination using google earth
Do you have any information about the accuraccy of google earth in order to measure declination? It can be excellent but as has been mentioned, your display may not be set? correctly to make it easy to achieve good accuracy. ? We had a conversation on this list some?time ago (10 Feb 2008)about the apparent mis-alignment of large horizontal dials when viewed on Google Earth. You can overcome this effect by using the placemark pins to establish the line of interest and then computing the declination from measurements on that line rather than reying on the GE Compass. Regards Patrick Don't let your email address define you - Define yourself at http://www.tunome.com today! --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Wall declination using google earth
Hello: You are talking about physical declinometers in order to know the wall declinations, I think that is the most acurrate method, but I have been using google earth, you can see the wall of the buildind or the aligned street, and could calculate the declination from North? (You have a rule to measure the x and y axis, or read the coordinates). What do you think about the accuracy of this method? Do you have any information about the accuraccy of google earth in order to measure declination? Best regards Damià --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Wall declination using google earth
Hello Damià You have to see how accurate is the satellite photo in google earth oriented with respect to the true north direction. Alex On Mon, Jun 8, 2009 at 2:53 PM, Damia Soler Estrela l...@damia.net wrote: Hello: You are talking about physical declinometers in order to know the wall declinations, I think that is the most acurrate method, but I have been using google earth, you can see the wall of the buildind or the aligned street, and could calculate the declination from North? (You have a rule to measure the x and y axis, or read the coordinates). What do you think about the accuracy of this method? Do you have any information about the accuraccy of google earth in order to measure declination? Best regards Damià --- https://lists.uni-koeln.de/mailman/listinfo/sundial --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Wall declination using google earth
I routinely use Google Earth to determine wall declination. Depending on the quality of the picture, resolution to within one degree can be achieved. The default orientation for Google Earth is straight north up for the center of the starting image. I have a flat screen with vertical sides and horizontal top and bottom that are useful reference lines. Check your screen settings. On most displays these days, x and y are not equal. I had to choose a display settings to match the dimensions of the monitor. There are examples of wall declination using Google Earth in some of the presentations on my website. Timelines #5 may be the most useful. Regards, Roger Bailey Walking Shadow Designs www.walkingshadow.info -- From: Damia Soler Estrela l...@damia.net Sent: Monday, June 08, 2009 5:53 AM To: Sundial List sundial@uni-koeln.de Subject: Wall declination using google earth Hello: You are talking about physical declinometers in order to know the wall declinations, I think that is the most acurrate method, but I have been using google earth, you can see the wall of the buildind or the aligned street, and could calculate the declination from North? (You have a rule to measure the x and y axis, or read the coordinates). What do you think about the accuracy of this method? Do you have any information about the accuraccy of google earth in order to measure declination? Best regards Damià --- https://lists.uni-koeln.de/mailman/listinfo/sundial No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.339 / Virus Database: 270.12.55/2160 - Release Date: 06/07/09 05:53:00 --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Google Wall Declination
On the thread of DeltaCad Macro, I have done some quite extensive macros for DeltaCad, for some sundial-related and other applications. When I encountered some sticky wickets with the code, I contacted DeltaCad and they informed me that they really don't handle Macro. They paid Cypress Software to provide a version of Basic that would work as a Macro for DeltaCad. When I contacted Cypress Software, they told me that they had a contract to provide DeltaCad with a Macro (Basic) engine and that was the extent of their commitment; it was not their policy to provide support for non-paying customers (like end users). I finally shamed someone at Cypress into answering my direct questions. (I even offered the results to the sundial mail list, but didn't receive any response. ) So I don't think John would get very much response from DeltaCad. And as John pointed out, his presentation should be his usual straight forward approach to sundial design rather than the details of Basic. I wish I could be there for the presentation, I am sure it will be good. Robert Hough ShadowMaster 32.37 N 111.13 W -- Original message -- From: John Carmichael [EMAIL PROTECTED] Hi Warren: Remember the NASS meeting in Hartford? That was the first meeting I went to and I met you. You were the person who turned me on to Delta Cad. Could you send me your article or pin down the issue it appeared in? Fred's schedule is jammed packed so I doubt that we can invite a software representative to talk. But I will try to do a good job. I don't know anything about scripting, whatever that is! (Does it have something to do with making macros?). My talk will be oriented to the people who just want to design sundials. I'll talk about using the popular sundial generator programs such as Shadows and Zonwvlak in conjunction with Delta Cad. And I'll talk about using existing available sundial macros, but not on how to make a macro. (I can't do that either). Mac Oglesby and Fer are the only guys on The List that I know who have made any sundial Delta Cad macros. Then finally, if I have time, I'll talk about bringing a DC drawing into Photoshop if you want to do special things to your drawing such as adding color or more artwork or transforming the drawing in other ways. We'll miss seeing you! John - Original Message - From: Warren Thom [EMAIL PROTECTED] To: John Carmichael [EMAIL PROTECTED]; Roger Bailey [EMAIL PROTECTED] Cc: Sundial List sundial@uni-koeln.de Sent: Thursday, July 20, 2006 12:45 PM Subject: Re: Google Wall Declination Hi John, Roger and all, I am sorry that I will miss the 2006 meeting - first one I will miss since 2001. Glad to hear you are putting on a DeltaCad workshop. I was unaware about version 6, until you posted your message, John. In checking it out, they are located near the meeting. I would urge someone to contact them and invite them to the NASS conference. Midnight Software, Inc., P.O. Box 77352 ,Seattle, WA 98177-0352 , USA They could do a talk on the scripting that is available in DeltaCad. Ron Anthony was in contact with them ages ago about the scripting language. For your workshop, you might photocopy the article I wrote about 10 years ago for the Compendium. I do think DeltaCad is easy to use --- and I spent hours at my school trying to learn AutoCad -- and never got very far. I printed something from DeltaCad after my first 15 minutes. (I have no interest in DeltaCad.) Take Care, Warren Thom - Original Message - From: John Carmichael To: Roger Bailey Hi Roger: you asked: I assume that your Delta Cad workshop will cover the transfer of Zon dxf files to Delta Cad. Yes, of course! That will be an important little part of my Delta Cad talk: How to import dxf, dwg and jpgs into a DC drawing. By the way, the new Delta Cad version 6.0 lets you import jpegs now. The older version would only let you import bmps. (which are huge files). This makes adding artwork/photos much easier and the files are smaller. You should upgrade to 6.0 if you haven't already done it. It has other useful features that 5.0 did not have. You might try importing a standard jpeg photo of your building wall in DC. Then copy and paste a the DC drawing of your sundial on top of it. You will see the DC sundial drawing on top of the photo. - Original Message - From: Roger Bailey [EMAIL PROTECTED] To: John Carmichael [EMAIL PROTECTED] Sent: Thursday, July 20, 2006 9:17 AM Subject: RE: Google Wall Declination Hi John, I assume that your Delta Cad workshop will cover the transfer of Zon dxf files to Delta Cad. The ability in Delta Cad to select all and copy to get the lines only as an overlay was a new one on me. Every other way I tried gave me an opaque white
RE: Google Wall Declination
To return to the original thread I have a couple of comments. Fer De Vries used the correct standard definition for shadow lengths for Islamic Prayer Times in Zon 2000. The analysis overlaying the Zon 2000 outputs on the picture of the sundials shows that there were local variations form those definitions. Since the prayer times evolved from folk astronomy, it is not surprising there are local variations. Originally the standard was based on a person's shadow and the length of the shadow measured with his feet. The legal and instrumental definitions based on local customs followed. The application to vertical declining sundials is a further, very interesting, step away from the folk astronomy roots. For more information check Joël Robic's great Sundial of the Month website, http://perso.orange.fr/cadrans.solaires/cadrans/cadrans-du-mois.html or more specifically, November 2005 Istanbul Mosque Sundials http://perso.orange.fr/cadrans.solaires/cadrans/cadran-istanbul-mosqu%E9es.h tml and December 2005 Istanbul Topkapi Palace. Roger Bailey -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Roger Bailey Sent: July 19, 2006 11:30 AM To: Sundial Mail List Subject: Google Wall Declination We have had many discussions on this list on how to determine the declination of a vertical wall. Let me suggest a new technique for not only wall declination but also location (latitude and longitude). Use the satellite images on Google Earth. An example is posted in three PowerPoint slides at: http://www3.telus.net/public/rtbailey/WalkingShadow/WallDecG.ppt For my Timelines presentation, I was interested in analysing sundials on mosques in Istanbul. When I took pictures of the three sundials on the New Mosque Yeni Camii, I did not take field measurements to determine the wall declination. No problem. Start up Google Earth and fly to Istanbul. Without rotating, just using the X/Y controls, zero in on the New Mosque and save the image. You can insert the saved image into a PowerPoint presentation, add the North South vertical axis, draw a line along the wall and determine the wall declination, perpendicular to the wall. Then start up Zon 2000 and enter the latitude and wall declination from the Google image into Fer de Vries program. Calculate for the example sundial: local hours, Italian hours and Islamic Prayer times. Clip the Zon drawing, save it as a dxf file and load the dxf file into Delta Cad. There you can trim the lines to recreate the dial on the wall. Select all and copy the lines as an overlay on the photograph (corrected for perspective) in your presentation. The Google Earth technique is sufficiently accurate with large buildings and high resolution images. I have used it successfully for three mosques in Istanbul and the Klementinum in Prague. It even works for my home! The full story will be shown in Vancouver. A conclusion from this analysis is the sundials on the mosques in Istanbul show the mid afternoon prayer time Asr as in the standard horizontal shadow length definition. But a different convention was used in Istanbul for Zuhr, the prayer just after noon. The Zuhr lines are not based on the altitude giving the horizontal shadow length as the noon shadow length + 25% of the vertical gnomon height. Regards, Roger Bailey Walking Shadow Designs N 48:38:22.90, W 123:24:10.80, declining east 90 degrees by Google Earth --- https://lists.uni-koeln.de/mailman/listinfo/sundial --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Google Wall Declination
Hi Roger: you asked: I assume that your Delta Cad workshop will cover the transfer of Zon dxf files to Delta Cad. Yes, of course! That will be an important little part of my Delta Cad talk: How to import dxf, dwg and jpgs into a DC drawing. By the way, the new Delta Cad version 6.0 lets you import jpegs now. The older version would only let you import bmps. (which are huge files). This makes adding artwork/photos much easier and the files are smaller. You should upgrade to 6.0 if you haven't already done it. It has other useful features that 5.0 did not have. You might try importing a standard jpeg photo of your building wall in DC. Then copy and paste a the DC drawing of your sundial on top of it. You will see the DC sundial drawing on top of the photo. - Original Message - From: Roger Bailey [EMAIL PROTECTED] To: John Carmichael [EMAIL PROTECTED] Sent: Thursday, July 20, 2006 9:17 AM Subject: RE: Google Wall Declination Hi John, I assume that your Delta Cad workshop will cover the transfer of Zon dxf files to Delta Cad. The ability in Delta Cad to select all and copy to get the lines only as an overlay was a new one on me. Every other way I tried gave me an opaque white background, useless as an overlay. This works for PowerPoint, not for Photoshop or Word. There you get the white background. See you soon, Roger -Original Message- From: John Carmichael [mailto:[EMAIL PROTECTED] Sent: July 20, 2006 7:07 AM To: Roger Bailey Subject: Re: Google Wall Declination Very Cool Roger! - Original Message - From: Roger Bailey [EMAIL PROTECTED] To: Sundial Mail List sundial@rrz.uni-koeln.de Sent: Wednesday, July 19, 2006 11:29 AM Subject: Google Wall Declination We have had many discussions on this list on how to determine the declination of a vertical wall. Let me suggest a new technique for not only wall declination but also location (latitude and longitude). Use the satellite images on Google Earth. An example is posted in three PowerPoint slides at: http://www3.telus.net/public/rtbailey/WalkingShadow/WallDecG.ppt For my Timelines presentation, I was interested in analysing sundials on mosques in Istanbul. When I took pictures of the three sundials on the New Mosque Yeni Camii, I did not take field measurements to determine the wall declination. No problem. Start up Google Earth and fly to Istanbul. Without rotating, just using the X/Y controls, zero in on the New Mosque and save the image. You can insert the saved image into a PowerPoint presentation, add the North South vertical axis, draw a line along the wall and determine the wall declination, perpendicular to the wall. Then start up Zon 2000 and enter the latitude and wall declination from the Google image into Fer de Vries program. Calculate for the example sundial: local hours, Italian hours and Islamic Prayer times. Clip the Zon drawing, save it as a dxf file and load the dxf file into Delta Cad. There you can trim the lines to recreate the dial on the wall. Select all and copy the lines as an overlay on the photograph (corrected for perspective) in your presentation. The Google Earth technique is sufficiently accurate with large buildings and high resolution images. I have used it successfully for three mosques in Istanbul and the Klementinum in Prague. It even works for my home! The full story will be shown in Vancouver. A conclusion from this analysis is the sundials on the mosques in Istanbul show the mid afternoon prayer time Asr as in the standard horizontal shadow length definition. But a different convention was used in Istanbul for Zuhr, the prayer just after noon. The Zuhr lines are not based on the altitude giving the horizontal shadow length as the noon shadow length + 25% of the vertical gnomon height. Regards, Roger Bailey Walking Shadow Designs N 48:38:22.90, W 123:24:10.80, declining east 90 degrees by Google Earth --- https://lists.uni-koeln.de/mailman/listinfo/sundial --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Google Wall Declination
Hi Warren: Remember the NASS meeting in Hartford? That was the first meeting I went to and I met you. You were the person who turned me on to Delta Cad. Could you send me your article or pin down the issue it appeared in? Fred's schedule is jammed packed so I doubt that we can invite a software representative to talk. But I will try to do a good job. I don't know anything about scripting, whatever that is! (Does it have something to do with making macros?). My talk will be oriented to the people who just want to design sundials. I'll talk about using the popular sundial generator programs such as Shadows and Zonwvlak in conjunction with Delta Cad. And I'll talk about using existing available sundial macros, but not on how to make a macro. (I can't do that either). Mac Oglesby and Fer are the only guys on The List that I know who have made any sundial Delta Cad macros. Then finally, if I have time, I'll talk about bringing a DC drawing into Photoshop if you want to do special things to your drawing such as adding color or more artwork or transforming the drawing in other ways. We'll miss seeing you! John - Original Message - From: Warren Thom [EMAIL PROTECTED] To: John Carmichael [EMAIL PROTECTED]; Roger Bailey [EMAIL PROTECTED] Cc: Sundial List sundial@uni-koeln.de Sent: Thursday, July 20, 2006 12:45 PM Subject: Re: Google Wall Declination Hi John, Roger and all, I am sorry that I will miss the 2006 meeting - first one I will miss since 2001. Glad to hear you are putting on a DeltaCad workshop. I was unaware about version 6, until you posted your message, John. In checking it out, they are located near the meeting. I would urge someone to contact them and invite them to the NASS conference. Midnight Software, Inc., P.O. Box 77352 ,Seattle, WA 98177-0352 , USA They could do a talk on the scripting that is available in DeltaCad. Ron Anthony was in contact with them ages ago about the scripting language. For your workshop, you might photocopy the article I wrote about 10 years ago for the Compendium. I do think DeltaCad is easy to use --- and I spent hours at my school trying to learn AutoCad -- and never got very far. I printed something from DeltaCad after my first 15 minutes. (I have no interest in DeltaCad.) Take Care, Warren Thom - Original Message - From: John Carmichael To: Roger Bailey Hi Roger: you asked: I assume that your Delta Cad workshop will cover the transfer of Zon dxf files to Delta Cad. Yes, of course! That will be an important little part of my Delta Cad talk: How to import dxf, dwg and jpgs into a DC drawing. By the way, the new Delta Cad version 6.0 lets you import jpegs now. The older version would only let you import bmps. (which are huge files). This makes adding artwork/photos much easier and the files are smaller. You should upgrade to 6.0 if you haven't already done it. It has other useful features that 5.0 did not have. You might try importing a standard jpeg photo of your building wall in DC. Then copy and paste a the DC drawing of your sundial on top of it. You will see the DC sundial drawing on top of the photo. - Original Message - From: Roger Bailey [EMAIL PROTECTED] To: John Carmichael [EMAIL PROTECTED] Sent: Thursday, July 20, 2006 9:17 AM Subject: RE: Google Wall Declination Hi John, I assume that your Delta Cad workshop will cover the transfer of Zon dxf files to Delta Cad. The ability in Delta Cad to select all and copy to get the lines only as an overlay was a new one on me. Every other way I tried gave me an opaque white background, useless as an overlay. This works for PowerPoint, not for Photoshop or Word. There you get the white background. See you soon, Roger -Original Message- From: John Carmichael [mailto:[EMAIL PROTECTED] Sent: July 20, 2006 7:07 AM To: Roger Bailey Subject: Re: Google Wall Declination Very Cool Roger! - Original Message - From: Roger Bailey [EMAIL PROTECTED] To: Sundial Mail List sundial@rrz.uni-koeln.de Sent: Wednesday, July 19, 2006 11:29 AM Subject: Google Wall Declination We have had many discussions on this list on how to determine the declination of a vertical wall. Let me suggest a new technique for not only wall declination but also location (latitude and longitude). Use the satellite images on Google Earth. An example is posted in three PowerPoint slides at: http://www3.telus.net/public/rtbailey/WalkingShadow/WallDecG.ppt For my Timelines presentation, I was interested in analysing sundials on mosques in Istanbul. When I took pictures of the three sundials on the New Mosque Yeni Camii, I did not take field measurements to determine the wall declination. No problem. Start up Google Earth and fly to Istanbul. Without rotating, just using the X/Y controls, zero in on the New Mosque and save the image. You can insert the saved image into a PowerPoint presentation, add the North
Google Wall Declination
We have had many discussions on this list on how to determine the declination of a vertical wall. Let me suggest a new technique for not only wall declination but also location (latitude and longitude). Use the satellite images on Google Earth. An example is posted in three PowerPoint slides at: http://www3.telus.net/public/rtbailey/WalkingShadow/WallDecG.ppt For my Timelines presentation, I was interested in analysing sundials on mosques in Istanbul. When I took pictures of the three sundials on the New Mosque Yeni Camii, I did not take field measurements to determine the wall declination. No problem. Start up Google Earth and fly to Istanbul. Without rotating, just using the X/Y controls, zero in on the New Mosque and save the image. You can insert the saved image into a PowerPoint presentation, add the North South vertical axis, draw a line along the wall and determine the wall declination, perpendicular to the wall. Then start up Zon 2000 and enter the latitude and wall declination from the Google image into Fer de Vries program. Calculate for the example sundial: local hours, Italian hours and Islamic Prayer times. Clip the Zon drawing, save it as a dxf file and load the dxf file into Delta Cad. There you can trim the lines to recreate the dial on the wall. Select all and copy the lines as an overlay on the photograph (corrected for perspective) in your presentation. The Google Earth technique is sufficiently accurate with large buildings and high resolution images. I have used it successfully for three mosques in Istanbul and the Klementinum in Prague. It even works for my home! The full story will be shown in Vancouver. A conclusion from this analysis is the sundials on the mosques in Istanbul show the mid afternoon prayer time Asr as in the standard horizontal shadow length definition. But a different convention was used in Istanbul for Zuhr, the prayer just after noon. The Zuhr lines are not based on the altitude giving the horizontal shadow length as the noon shadow length + 25% of the vertical gnomon height. Regards, Roger Bailey Walking Shadow Designs N 48:38:22.90, W 123:24:10.80, declining east 90 degrees by Google Earth --- https://lists.uni-koeln.de/mailman/listinfo/sundial
RE: Zarbula's Method for Wall Declination
Hi Mac, Chicago, 19-21 August 2005, NASS conference. Roger Hi Roger, Are you going to leave us dangling, or are you willing to tell us how Zarbula found SH with a stick, some string and the Sun? Best wishes, Mac Roger Bailey wrote: (snip) Similarly you can calculate the Sub-style Height, the angle of the gnomon to the wall, as Sin SH = Cos Dec x Cos Lat. But this is not how Zarbula did it. He only had available a stick, some string and the sun. I will leave that as a homework exercise. - -
Re: Zarbula's Method for Wall Declination
I am not sure to understand Zarbula and Indian circle methods but perhaps this can help for your last question. I know this relation is validated : sin (D) = tan (X) / tan (L) D = wall declination X = angle between the equinoctial line and an horizontal line L = Latitude But I am not sure of this other one: sin (D) = tan (Y)* tan (L) Y = angle between equinoctial line and the substyle line But it seems to works with your examples Example 2 : sin (D = 45) = 0,707 tan (Y = 48.2) = 1.118 tan ( L = 32.3) = 0.632 Example 3 sin (90) = 1 tan (Y = 57,7) = 1;581 tan ( L = 32.3) = 0.632 Perhaps can you test this with other angles Best regards Joël 48°01'20 N, 1°46' W (FRANCE) http://www.cadrans-solaires.fr/ - Original Message - From: John Carmichael [EMAIL PROTECTED] To: Roger Bailey [EMAIL PROTECTED] Cc: Sundial List sundial@rrz.uni-koeln.de Sent: Saturday, December 04, 2004 5:46 PM Subject: Re: Zarbula's Method for Wall Declination Hi Roger: I followed your whole letter with great interest, and understand it all, except for one thing. Is it possible to determine the wall's declination once I have drawn the equinoctial line and the substyle line using this method? At first I thought that if I drew a horizontal line on the paper and determined the angle of the sloping equinoctial line, that this angle would equal the wall's declination, but it doesn't in all the examples I've tested. For examples, I played around with a sundial drawing program and entered different wall declinations (0, 45 and 90 degrees East of South) for my latitude 32.3 deg N. and then I measured the sloping angle of the equinoctial lines. Here are the results: 1. If the wall is due south, then the equinoctial line is horizontal which means the declination is 0. so far so good. 2. But if the wall declines say 45 degrees to the East of South, and I draw a sundial face using Shadows or Zonwvlak, then I thought it's angle is should be 45 also, but it's not. It's 48.2 degrees. 3. If I draw a dial the declines 90 degrees East of South, then the angle of the equinoctial line should be 90, but it's not. It's 57.7 degrees. So obviously my supposition is wrong. The angle of the equinoctial line is NOT equal to the wall declination. How can I get the wall declination using your Indian Circle method? Thanks John - Original Message - From: Roger Bailey [EMAIL PROTECTED] To: Sundial Mail List sundial@rrz.uni-koeln.de Sent: Friday, December 03, 2004 9:42 PM Subject: Zarbula's Method for Wall Declination Hello Colleagues, The Piedmontese painter and sundial maker, Giovanni Francesco Zarbula left an amazing legacy in the villages of the French alps. Between 1832 and 1870 he crafted over 60 sundials in the area from Grenoble to Gap, near the Italian border. Over half of these flamboyant folk art masterpieces still survive; recently many have been expertly restored. I often wondered how Zarbula laid out these designs on vertical declining walls. As an itinerant craftsman, carrying all the tools of his trade on the back of a mule, he would not be able to utilize the methods summarized in Frank King's note following John Carmichael's good question. How did he do it? I am pleased to report that Google found the answer for me. Follow the link to: http://www.meridianeitaliane.it/Rivista%20Gnomonica/gnomonica6.pdf On pages 8- 10 of this 61 page edition of Gnomonica, there is a letter by Alessandro Gunella outlining Zarbula's method: L'orolgio Francese e il metodo DI ZARBULA per trovare la declinazione del muro. Thanks, Alessandro for answering the question. I guess that I am not the first to be impressed by Zarbula's dials and wonder about his techniques. As Alessandro reported, Zarbula didn't actually measure the declination of the wall. He didn't need to. Zarbula seems to have applied a variation of the Indian Circle technique (Cassini's Method on Frank King's list) to establish the equinoctial and sub-style line on the wall. From these he could lay out the hour lines using well known graphical gnomonic techniques. The Indian Circle method (cerchio indu in Italian) is a simple technique for finding north. All you need is a stick, a string and sunshine. Put the stick vertically into the flat level ground. Use the string to describe some circular arcs, using the stick as the center. Watch the shadow of the tip of the stick and note where the path of the shadow tip crosses the arc in the morning and then again in the afternoon on the other side of the circle. The line between the crossing points is due east - west. North - south is perpendicular to the east - west line. Zarbula's method is based on the fact that every vertical declining sundial has an analogous horizontal sundial somewhere else in the world. To apply this variation to a declining wall, all you have to do is mount a stick perpendicular to the wall, draw one or more concentric arcs, mark
RE: Zarbula's Method for Wall Declination
Hi John, It is back to the basics on this one: Waugh, Chapter 10, Page 79, Verse 1 to 4. The concepts of Sub-style Distance (SD), Sub-style Height (SH), Difference in Longitude (DL) and Angle with the Vertical (AV) so well developed in Waugh, are not evident in the computer programs that we now commonly use. You can determine the wall declination from the Sub-Style distance if you know the latitude as Tan SD = Sin Dec / Tan Lat. The Sub-style Distance is the angle from the sub-style line to the vertical. This is the same angle that the perpendicular to the sub-style, the equinoctial, line, makes with the horizontal. As wall declination increases from zero, the sub-style distance (and equinoctial angle) increase but at a reduced rate, reaching a maximum, equal to the co-latitude, when the declination is 90 degrees. Using your examples and your latitude of 32.3 degrees and Tan Lat = 0.632: Dec = 0, Sin Dec = 0, Tan SD = 0 Dec = 45, Sin Dec = 0.707, Tan SD = 0.707/.632 = 1.118, SD = 48.2 Dec = 90, Sin Dec = 1, Tan SD = 1 / 0.632 = 1.582, SD = 57.7, or your co-latitude. Zarbula had it easy as he worked at latitude 45 degrees where the Tan = 1. For him, Tan SD = Sin Dec. Similarly you can calculate the Sub-style Height, the angle of the gnomon to the wall, as Sin SH = Cos Dec x Cos Lat. But this is not how Zarbula did it. He only had available a stick, some string and the sun. I will leave that as a homework exercise. Regards, Roger Bailey Walking Shadow Designs N 48.6 W123.4 -Original Message- From: John Carmichael [mailto:[EMAIL PROTECTED] Sent: December 4, 2004 8:46 AM To: Roger Bailey Cc: Sundial List Subject: Re: Zarbula's Method for Wall Declination Hi Roger: I followed your whole letter with great interest, and understand it all, except for one thing. Is it possible to determine the wall's declination once I have drawn the equinoctial line and the substyle line using this method? At first I thought that if I drew a horizontal line on the paper and determined the angle of the sloping equinoctial line, that this angle would equal the wall's declination, but it doesn't in all the examples I've tested. For examples, I played around with a sundial drawing program and entered different wall declinations (0, 45 and 90 degrees East of South) for my latitude 32.3 deg N. and then I measured the sloping angle of the equinoctial lines. Here are the results: 1. If the wall is due south, then the equinoctial line is horizontal which means the declination is 0. so far so good. 2. But if the wall declines say 45 degrees to the East of South, and I draw a sundial face using Shadows or Zonwvlak, then I thought it's angle is should be 45 also, but it's not. It's 48.2 degrees. 3. If I draw a dial the declines 90 degrees East of South, then the angle of the equinoctial line should be 90, but it's not. It's 57.7 degrees. So obviously my supposition is wrong. The angle of the equinoctial line is NOT equal to the wall declination. How can I get the wall declination using your Indian Circle method? Thanks John -
Zarbula's Method for Wall Declination
Hello Colleagues, The Piedmontese painter and sundial maker, Giovanni Francesco Zarbula left an amazing legacy in the villages of the French alps. Between 1832 and 1870 he crafted over 60 sundials in the area from Grenoble to Gap, near the Italian border. Over half of these flamboyant folk art masterpieces still survive; recently many have been expertly restored. I often wondered how Zarbula laid out these designs on vertical declining walls. As an itinerant craftsman, carrying all the tools of his trade on the back of a mule, he would not be able to utilize the methods summarized in Frank King's note following John Carmichael's good question. How did he do it? I am pleased to report that Google found the answer for me. Follow the link to: http://www.meridianeitaliane.it/Rivista%20Gnomonica/gnomonica6.pdf On pages 8- 10 of this 61 page edition of Gnomonica, there is a letter by Alessandro Gunella outlining Zarbula's method: L'orolgio Francese e il metodo DI ZARBULA per trovare la declinazione del muro. Thanks, Alessandro for answering the question. I guess that I am not the first to be impressed by Zarbula's dials and wonder about his techniques. As Alessandro reported, Zarbula didn't actually measure the declination of the wall. He didn't need to. Zarbula seems to have applied a variation of the Indian Circle technique (Cassini's Method on Frank King's list) to establish the equinoctial and sub-style line on the wall. From these he could lay out the hour lines using well known graphical gnomonic techniques. The Indian Circle method (cerchio indu in Italian) is a simple technique for finding north. All you need is a stick, a string and sunshine. Put the stick vertically into the flat level ground. Use the string to describe some circular arcs, using the stick as the center. Watch the shadow of the tip of the stick and note where the path of the shadow tip crosses the arc in the morning and then again in the afternoon on the other side of the circle. The line between the crossing points is due east - west. North - south is perpendicular to the east - west line. Zarbula's method is based on the fact that every vertical declining sundial has an analogous horizontal sundial somewhere else in the world. To apply this variation to a declining wall, all you have to do is mount a stick perpendicular to the wall, draw one or more concentric arcs, mark the shadow tip crossings on the wall, and draw a straight line through them. This line is the equinoctial line, (equinoziale in Italian), the intersection of the equatorial plane with the plane of the vertical declining wall. This important construction line is highlighted in most of Zarbula's dials. A perpendicular line from the equinoctial is the sub-style line (sostilare in Italian) for the polar axis parallel. QED I hope that I got this right as I used Babblefish to transliterate Alessandro's note and some points may have been lost in translation. The web link brings up the whole pdf file, 3.6 MB. If any one wants to have a copy of the extracted pages, a 60 kb file and/or my interpreted translation based on Babblefish, I would be pleased to send them on as email attachments. I assume Alessandro Gunella or Nicola Severino of Gnomonica will allow such single copies to colleagues within the copyright laws. I am continuing my research on Zarbula, his methods and his dials. If any one has information to share on these topics that doesn't come up among the ~200 Google hits on Zarbula, I would appreciate a note. Regards, Roger Bailey Walking Shadow Designs Now back at N 48.6 W 123.4 -
Re: Wall Declination Measurement
Dear Alex, Thank you for your rapid reply... As architect my comment on no.1. is that the north arrow which we place in drawings (at least the ones I place) are based on the North direction on large scale survey maps supplied by planning authorities and on which the drawing would be based. That certainly makes sense. Here in the U.K. we would have to know whether the large scale map used true north or grid north but, subject to that caveat, your arrow ought to be within a degree or two of being right. The main reason for errors of 15 degrees or so seems to be a result of modern surveying practice using instruments which measure distance as well as angle... What seems to happen is that the surveyor takes ONE primary point on a building site and marks this on the ground with a pin and a little circle. This is the origin of an x,y,z coordinate system in which positive z is vertically up and the x-y plane is horizontal. This still lacks an orientation. In theory, positive y is due north and positive x is due east. Surveyors don't actually use the letters x, y, and z but talk about Easting, Northing and Height respectively. I have watched these guys at work. When they start off, they choose a reference origin quite carefully (you don't want a spot which is going to be built over or have huts on it) but they are much less fussy about orientation. They will simply guess which way is north (or east if that is more convenient) and slap a target on a wall and use that as their reference orientation for the whole construction period. If it is 15 degrees out no one seems to mind! Maybe surveying practice is more rigorous in Malta! Frank -
Re: Wall Declination Measurement
Dear Mr King, Interesting post. As architect my comment on no.1. is that the north arrow which we place in drawings (at least the ones I place) are based on the North direction on large scale survey maps supplied by planning authorities and on which the drawing would be based. Errors of 15 degrees are quite serious in this respect, even though one should always take the arrow only as a general indication of north and not for accurate sundial work, for which I would favour four trials (a few days apart) of Waugh's technique from his book. Best regards Alex Malta 1. Architect's Drawings A typical Architect's site plan includes a very convincing ornamented letter N enfolding an arrow. The arrow usually points at some arbitrary angle with respect to the sides of the paper. Alas, the angle is also pretty arbitrary with respect to true north. I have known errors up to 15 degrees. Verdict: Avoid like the plague
Re: Wall Declination Measurement
I have been enjoying the comments on estimating wall declination, especially those which have the ring of experience about them. I am prompted to offer the following Consumer Guide to the methods I have used over the years (and two I haven't). I am sure that many readers will be able to add to my list: 1. Architect's Drawings A typical Architect's site plan includes a very convincing ornamented letter N enfolding an arrow. The arrow usually points at some arbitrary angle with respect to the sides of the paper. Alas, the angle is also pretty arbitrary with respect to true north. I have known errors up to 15 degrees. Verdict: Avoid like the plague 2. Large-Scale Maps Good maps may well stem from very careful surveys but the representations of buildings are often more suggestive than accurate. You can often determine latitude and longitude to high precision but should treat the orientation of a depicted wall with great caution. You also have to worry (in the U.K.) about distinguishing grid north from true north. Verdict: Avoid 3. Magnetic compass Subject to numerous caveats you ought to be able to get good results. You have to be sure that there isn't a hidden iron drain or some such nearby and, of course, you need to know the local magnetic variation. The method is no use if the magnetic dip is too large. Verdict: Avoid 4. Using Solar Azimuth - General Carol Arnold, John Davies, Tony Moss and Bill Gottesman have described variants of the same idea: use the sun! I have used all these and more. I am not keen on plumb lines [they don't keep still and if you use a bucket of water to dampen the swings you just get a bowed string!]. If you make many observations widely spaced in hour-angle you can get a result better than 10 arc-minutes. Verdict: Fair to Good 5. Using Solar Azimuth - Window Ledge Method If you simply place a sheet of paper on a window ledge with one edge firmly against the inside of the bottom of the window frame you can often get the vertical edge of the window frame or a vertical glazing bar to cast a shadow. You draw a line just ahead of the (moving) shadow and note the time that the shadow reaches the line. Typical window ledges are close to horizontal and the sides of windows are approximately vertical so this can be quite accurate. Verdict: Fair 6. Using Solar Azimuth - Letting the client do it What do you do if you have to rely on someone else? The instructions I have given overseas clients (for example) are as follows: Find a flat board, a sheet of squared paper, a spirit level, a wooden pencil and a digital clock (preferably one that is radio-controlled and shows the date as well as the time). Place the board against the wall and place the squared paper on the board with one edge against the wall. Place the clock on the piece of paper. Check that the board is level and stand a pencil so that it balances on its blunt end (this is an added check that the board is level). Arrange that the pencil casts a shadow that falls across the squared paper. Take several digital photographs (preferably over several hours) which show the paper, the pencil, the shadow and the clock. E-mail me the results the same day. By counting squares I can get a reasonable estimate of the angle the shadow makes to the wall. The rest is as for 4 and 5. Make sure that you know how the time on the clock relates to UTC. Verdict: Fine if there is no other way 6. Using GPS An up-market approach using GPS kit exploits two GPS receivers each slaved to the other so that the relative phase-angles of the signals received from each satellite can be compared. You let the system run for 6 hours or so and via a good deal of software you can determine the position or one receiver relative to the other to about 5mm. Their absolute positions will not be known to such precision but that doesn't matter. Using a 50m baseline, a 5mm error means you can determine the azimuth of the baseline to about 20 arc-seconds. You then use standard surveying techniques to find the declination of your wall. You have to take care not to get stray reflections so you should be high up on something solid. Scaffolding will not do! This works splendidly even if it is cloudy. The snag is the cost. The kit costs about $80,000 and is obviously expensive to hire. It is suitable for high-budget sundials only! Verdict: Wonderful if you have a rich client 7. Cassini Method When setting out camera obscura noon marks a technique, which I think is due to Cassini, is first to note the point on the floor perpendicularly below the hole in the roof (immensely difficult to determine accurately) and then draw concentric circles round that point. Next you plot the hyperbolic path followed
Wall Declination Measurement
Hello Carol: (c.c Sundial List) I'm back home and this morning I'm looking at your wall declination measurements. Unfortunately, I am not accustomed to using the nail method you used and I hesitate to comment because I don't want to make a mistake. I have heard of this method however. I am going to forward your letter to our Sundial List discussion group and hopefully somebody there will be able to check your measurements. But I was able to check your solar azimuth data that you got from your astronomy program. According to the program I use (The Dialist Companion), the solar azimuth at that latitude, longitude and time was about 20.45 degrees west of south, not 209 degrees. Just think about it. If the solar declination were 180 degrees west of south, the sun would be due north and that's not possible. 209 degrees would be towards the North East which is also impossible. Hopefully, somebody from the sundial list will help us. John - Original Message - From: carol arnold To: John Carmichael Sent: Monday, November 22, 2004 1:09 PM Subject: declination John, I was just having a go at measuring the declination of a window in my house - I am not convinced of the accuracy of my measurement of sun angle to wall,but I wondered if you could double check the calcualtions? The window was approx south facing. 22 nov 2004 at14.01 gmt I used a nail 92mm long on a vertical board and its shadow was 50mm to the right of the nail. So the sun angle to the wall is 28 deg 31min 23sec west of south. My astronomy program gave me azimuth of sun to be 209 deg 44min 31sec ie 29deg 44min 31sec west of south, for lat 51deg 25min 20sec North and long 2 deg 42 min 30 sec west. So I reckon the the wall faces 1 deg 13 min 8 sec west of south?? Regards and hope you dont mind my asking you about this, Carol Carol Arnold Stained glass artist, commissions welcome, please takea look at my stained glass websitehttp://www.carolarnold.co.uk Moving house? Beach bar in Thailand? New Wardrobe? Win £10k with Yahoo! Mail to make your dream a reality.
Re: Wall Declination Measurement
Hello John , the values written by Carol are all correct and very accurate and her wall faces exactly 1 deg 13 8 west of south In astronomy the azimuth values start from north and therefore a value of 209 deg corresponds, for the dialist, to 29 degs from South toward West. Regards Gianni Ferrari 44° 39' N 10° 55' EMailto : [EMAIL PROTECTED] - Original Message - From: John Carmichael To: carol arnold Cc: Sundial List Sent: Monday, November 29, 2004 2:55 PM Subject: Wall Declination Measurement Hello Carol: (c.c Sundial List) I'm back home and this morning I'm looking at your wall declination measurements. Unfortunately, I am not accustomed to using the nail method you used and I hesitate to comment because I don't want to make a mistake. I have heard of this method however. I am going to forward your letter to our Sundial List discussion group and hopefully somebody there will be able to check your measurements. But I was able to check your solar azimuth data that you got from your astronomy program. According to the program I use (The Dialist Companion), the solar azimuth at that latitude, longitude and time was about 20.45 degrees west of south, not 209 degrees. Just think about it. If the solar declination were 180 degrees west of south, the sun would be due north and that's not possible. 209 degrees would be towards the North East which is also impossible. Hopefully, somebody from the sundial list will help us. John - Original Message - From: carol arnold To: John Carmichael Sent: Monday, November 22, 2004 1:09 PM Subject: declination John, I was just having a go at measuring the declination of a window in my house - I am not convinced of the accuracy of my measurement of sun angle to wall,but I wondered if you could double check the calcualtions? The window was approx south facing. 22 nov 2004 at14.01 gmt I used a nail 92mm long on a vertical board and its shadow was 50mm to the right of the nail. So the sun angle to the wall is 28 deg 31min 23sec west of south. My astronomy program gave me azimuth of sun to be 209 deg 44min 31sec ie 29deg 44min 31sec west of south, for lat 51deg 25min 20sec North and long 2 deg 42 min 30 sec west. So I reckon the the wall faces 1 deg 13 min 8 sec west of south?? Regards and hope you dont mind my asking you about this, Carol Carol Arnold Stained glass artist, commissions welcome, please takea look at my stained glass websitehttp://www.carolarnold.co.uk Moving house? Beach bar in Thailand? New Wardrobe? Win £10k with Yahoo! Mail to make your dream a reality.
Re: Wall Declination Measurement
I think the measurement of the wall declination with the nail method done by Caroil is correct. The azimuth of the sun is 29deg 44min 31sec west of south on the mentioned place and time. And thus the wall declination is: 29deg 44min 31sec - 28 deg 31min 23sec = 1 deg 13 min 8 sec west of south Willy Leenders Hasselt, Flanders in Belgium John Carmichael wrote: Hello Carol: (c.c Sundial List)I'm back home and this morning I'm looking at your wall declination measurements. Unfortunately, I am not accustomed to using the nail method you used and I hesitate to comment because I don't want to make a mistake. I have heard of this method however. I am going to forward your letter to our Sundial List discussion group and hopefully somebody there will be able to check your measurements.But I was able to check your solar azimuth data that you got from your astronomy program. According to the program I use (The Dialist Companion), the solar azimuth at that latitude, longitude and time was about 20.45 degrees west of south, not 209 degrees. Just think about it. If the solar declination were 180 degrees west of south, the sun would be due north and that's not possible. 209 degrees would be towards the North East which is also impossible.Hopefully, somebody from the sundial list will help us.John - Original Message - From: carol arnold To: John Carmichael Sent: Monday, November 22, 2004 1:09 PM Subject: declination John, I was just having a go at measuring the declination of a window in my house - I am not convinced of the accuracy of my measurement of sun angle to wall,but I wondered if you could double check the calcualtions? The window was approx south facing.22 nov 2004 at14.01 gmtI used a nail 92mm long on a vertical board and its shadow was 50mm to the right of the nail. So the sun angle to the wall is 28 deg 31min 23sec west of south.My astronomy program gave me azimuth of sun to be 209 deg 44min 31sec ie 29deg 44min 31sec west of south, for lat 51deg 25min 20sec North and long 2 deg 42 min 30 sec west.So I reckon the the wall faces 1 deg 13 min 8 sec west of south??Regards and hope you dont mind my asking you about this,Carol Carol ArnoldStained glass artist, commissions welcome,please take a look at my stained glass website http://www.carolarnold.co.uk Moving house? Beach bar in Thailand? New Wardrobe? Win 10k with Yahoo! Mail to make your dream a reality.
Re: Wall Declination Measurement
Gianna got in before me with the answer to your question. I use a version of the "nail in a board" method myself. I like to take several measurements, preferably over a couple of hours, to improve the accuracy of the measurement. As well as the horizontal position, I also record the vertical position of the shadow tip below the base ot the "nail". This can be compared with the sun's altitude and proves a useful double-check, allowing doubtful readings to be discarded. Regards, John --John Carmichael [EMAIL PROTECTED] wrote: Hello Carol: (c.c Sundial List) I'm back home and this morning I'm looking at your wall declination measurements. Unfortunately, I am not accustomed to using the nail method you used and I hesitate to comment because I don't want to make a mistake. I have heard of this method however. I am going to forward your letter to our Sundial List discussion group and hopefully somebody there will be able to check your measurements. But I was able to check your solar azimuth data that you got from your astronomy program. According to the program I use (The Dialist Companion), the solar azimuth at that latitude, longitude and time was about 20.45 degrees west of south, not 209 degrees. Just think about it. If the solar declination were 180 degrees west of south, the sun would be due north and that's not possible. 209 degrees would be towards the North East which is also impossible. Hopefully, somebody from the sundial list will help us. John - Original Message - From: carol arnold To: John Carmichael Sent: Monday, November 22, 2004 1:09 PM Subject: declination John, I was just having a go at measuring the declination of a window in my house - I am not convinced of the accuracy of my measurement of sun angle to wall,but I wondered if you could double check the calcualtions? The window was approx south facing. 22 nov 2004 at14.01 gmt I used a nail 92mm long on a vertical board and its shadow was 50mm to the right of the nail. So the sun angle to the wall is 28 deg 31min 23sec west of south. My astronomy program gave me azimuth of sun to be 209 deg 44min 31sec ie 29deg 44min 31sec west of south, for lat 51deg 25min 20sec North and long 2 deg 42 min 30 sec west. So I reckon the the wall faces 1 deg 13 min 8 sec west of south?? Regards and hope you dont mind my asking you about this, Carol Carol Arnold Stained glass artist, commissions welcome, please takea look at my stained glass websitehttp://www.carolarnold.co.uk Moving house? Beach bar in Thailand? New Wardrobe? Win £10k with Yahoo! Mail to make your dream a reality.Dr J R DavisFlowton DialsN52d 08m: E1d 05m
Re: Wall Declination Measurement
John Carmichael wrote: Subject: Wall Declination Measurement Hopefully, somebody from the sundial list will help us. This is my own preferred method of determining wall declination but, before originally adopting it, I needed to be sure that a) the 'nail' was truly pependicular to the measuring board and b) the plumbline/pencil line ran exactly through the axis of the nail. Without this certainty the results might be questionable so to that end I developed my 'precision declinometer' which I know has been adopted in various forms by other diallists. It uses a tapered 'gnomon' spike sliding in a machined vee groove*. The novel idea was to include a needle point in the butt end of the spike which punctures the recording paper exactly on its axis. For anyone who missed the previous offer via this list some years ago I can supply a gif and jpeg showing how it is made and used. Like John Davis I also prefer to take a number of readings over an extended period then take an average. * An accurately drill hole is almost as good but 'drilling is the least precise process in engineering' and unless a good sliding fit is obtained then the tip and needle point can wobble off centre whereas a vee groove constrains the spike precisely in two perpendicular planes. Tony Moss -
Re: Wall Declination Measurement
I wrote a program that determines declination of a vertical wall using just a watch and a carpenter's square. It gives very accurate results if performed when the square's shadow is long. Be certain to follow directions closely, and measure the edge of the shadow as described in the method. Take a few measurements for consistency. Download it free at www.precisionsundials.com/walldeclination.exe Bill G. -
Re: Wall Declination Measurement
I've got that drawing of your somewhere but I can't locate it. Could you please send me a copy? thanks John - Original Message - From: tony moss [EMAIL PROTECTED] Cc: Sundial List sundial@rrz.uni-koeln.de Sent: Monday, November 29, 2004 9:46 AM Subject: Re: Wall Declination Measurement John Carmichael wrote: Subject: Wall Declination Measurement Hopefully, somebody from the sundial list will help us. This is my own preferred method of determining wall declination but, before originally adopting it, I needed to be sure that a) the 'nail' was truly pependicular to the measuring board and b) the plumbline/pencil line ran exactly through the axis of the nail. Without this certainty the results might be questionable so to that end I developed my 'precision declinometer' which I know has been adopted in various forms by other diallists. It uses a tapered 'gnomon' spike sliding in a machined vee groove*. The novel idea was to include a needle point in the butt end of the spike which punctures the recording paper exactly on its axis. For anyone who missed the previous offer via this list some years ago I can supply a gif and jpeg showing how it is made and used. Like John Davis I also prefer to take a number of readings over an extended period then take an average. * An accurately drill hole is almost as good but 'drilling is the least precise process in engineering' and unless a good sliding fit is obtained then the tip and needle point can wobble off centre whereas a vee groove constrains the spike precisely in two perpendicular planes. Tony Moss - -
Wall Declination Software
Now that CardinalDirections.exe is running so nicely, it was not hard to adapt the code to perform calculations for accurately measuring the declination of a vertical wall. The method is simple, requiring just a carpenter's square and a watch. You can check it out by downloading WallDeclination.exe from www.precisionsundials.com/software.htm. The method is sketched in the program, and is described in detail in Wall Declination.doc on the same software page. As usual, suggestions are welcomed. -Bill -
Re: Wall Declination Software
Just a practical remark for both of your programs: You mention the date format as mm/dd/ and the time format as H:M:S AM/PM but the programs accept only the date and time formats as defined in the Regional Options of the Control Panel on your PC. Thibaud Chabot At 10:20 03-09-2003 -0400, you wrote: Now that CardinalDirections.exe is running so nicely, it was not hard to adapt the code to perform calculations for accurately measuring the declination of a vertical wall. The method is simple, requiring just a carpenter's square and a watch. You can check it out by downloading WallDeclination.exe from www.precisionsundials.com/software.htm. The method is sketched in the program, and is described in detail in Wall Declination.doc on the same software page. As usual, suggestions are welcomed. -Bill - -
Corrected Method for finding Wall Declination
I have put the corrected method for finding wall declination on my website (the handout from the NASS conference had significant errors). Go to www.precisionsundials.com/software.htm and download Wall Declination.doc. It is an MSWord Document. You can also download an MSWorks spreadsheet to assist the calculations called WallDec.wks. I hope this time I've got all the bugs out. Bill G. -
Error in my conference Wall Declination Formula.
Dear 2002 Conference attendees, John Carmichael tried my wall declination formula, and it did not work because I mistakenly put a minus sign where it didn't belong. I'm sorry to make an error in a method that was supposed to be so simple. The Correct formula is Wall Dec. = A +/-ArcCos[Sin(C)/Cos(B)], NOT Wall Dec. = -A +/-ArcCos[Sin(C)/Cos(B)]. Note the minus sign before A has been removed. Please correct this on your handout. To the list members who were not at the conference, I apologize for the irrelevance of this message. Bill Gottesman -
Re: wall declination recipes
Hi Roger Excuse me for not commenting on your wall declination recipe sooner, but it has been in the back of my mind. What do you mean when you say: a convenient perpendicular. I'm having a hard time visualizing the envelope, the wall, the perpendicular and the sun. I'm assuming that these results let you use the solar azimuth/altitude formula that you use so often? John John L. Carmichael Jr. Sundial Sculptures 925 E. Foothills Dr. Tucson Arizona 85718 USA Tel: 520-696-1709 Email: [EMAIL PROTECTED] Website: http://www.sundialsculptures.com - Original Message - From: Roger Bailey [EMAIL PROTECTED] To: sundial@rrz.uni-koeln.de Sent: Tuesday, July 30, 2002 8:26 PM Subject: RE: wall declination recipes I agree with Claude's comments The many notes about this subject only points out its importance but we have to appreciate individual differences. I can put an old envelope against a wall or window, align the shadow of a convenient perpendicular and check the time. This gives me everything I need to determine the declination of a wall. But if you have not set your watch by the atomic clock, read Bowditch before breakfast or Rohr before resting, you cannot do this. You will need to follow a detailed incomprehensible recipe. Miss one critical step and the project is a flop. My wife can go to the local market to buy what is in season, add from the pantry Je ne sais quoi and create from scratch a gourmet meal. When in the kitchen, I need to follow a detailed incomprehensible recipe. I am sure to miss one critical step and the meal is a flop. We have different talents. Vive la difference even if it makes it hard for us to market custom sundials. The wonderful feature of this mailing list is that we are from different backgrounds, languages and cultures but we share this interest and understanding of gnonomics. Amazing! Roger Bailey Walking Shadow Designs N 51 W 115 - -
RE: wall declination recipes
I agree with Claude's comments The many notes about this subject only points out its importance but we have to appreciate individual differences. I can put an old envelope against a wall or window, align the shadow of a convenient perpendicular and check the time. This gives me everything I need to determine the declination of a wall. But if you have not set your watch by the atomic clock, read Bowditch before breakfast or Rohr before resting, you cannot do this. You will need to follow a detailed incomprehensible recipe. Miss one critical step and the project is a flop. My wife can go to the local market to buy what is in season, add from the pantry Je ne sais quoi and create from scratch a gourmet meal. When in the kitchen, I need to follow a detailed incomprehensible recipe. I am sure to miss one critical step and the meal is a flop. We have different talents. Vive la difference even if it makes it hard for us to market custom sundials. The wonderful feature of this mailing list is that we are from different backgrounds, languages and cultures but we share this interest and understanding of gnonomics. Amazing! Roger Bailey Walking Shadow Designs N 51 W 115 -
wall declination
Hi everybody, here is my modest contribution to the subject, according the old method (thanks to Alain Mory) it is based on finding the local meridian in front of the wall. If the floor in front of the wall is well horizontal you can use it right away, if not you have to put a flat stone or board on the ground put it horizontal in every way. Lets say the lenght of the board is 65cm in the direction south/north, mount a style of +/- 20cm vertically on the south end of the board; on top of the style you attach a small plate in such a manner that the angle plate/board is = local lattitude; in the small plate you drill a hole of +/- 3mm. With a plumbers weight you find the vertical projection of that hole on the board, that is the first point of the local meridian. Then around 9 in the morning you mark the spot of the gnomons hole on the board; with as radius the first point of the meridian this spot you draw part of a circle that goes to the right up till the edge of the board.If the first spot was obtained say at 9h 7min or 2h 53min before noon, the image of the sun will appear again on the same circle in a different position, at 2h 53min after noon. So a little before that hour you observe the spot, when it is on the circle, you mark it. Then you join both spots with a line, determine the middle, which is the second point of the meridian. Prolong this meridian line up to the wall is not difficult provided you do it with a helper to taughten the thin cord check its position over the meridian.The angle made by this line the orthogonal on the wall is the declination value of the wall. If you have doubts about the wall being well vertical plane, one can allways use a marine plywood board about the size of the future sundial, put it well vertical, mark the footprint on the ground with several points, measure the angle to that board later install that board on the wall in exactly the same position with plumbers weights glass level. Thank you for reading all this, Walter -
Re: wall declination
The many notes about this subject only points out its importance. In the September 2001 issue of the NASS compendium there was included an article by Gianni Ferrari on methods for finding the orientation of a plane using the sun. The digital edition included his program WallDec that uses about 8 different methods. In correspondence with Gianni he reported that he often has helped people who were using his programs. He said he sends them the times of solar transit for their location and asks them to use his small board method which finds the angle the sun's shadow makes with the wall at that time. They merely telephone him with the information. He says this nearly always has worked and has done so 15 to 20 times. My recent experience with trying to determine the declination of a client's wall by e-mail reflects the many cautions of others. Don't expect many to follow even good instructions! Above all, don't expect them to set or even read their own watch correctly. Send them a digital watch. I would not send them a camera. You might get a lot of fuzzy out of focus images. Here is my own tale of woe: I asked that a surveyor find which way the wall faces. He reported 84.16 degrees! I knew from the client that the wall faced somewhat South and that must mean a declination of 5.86 degrees to the east. I made a test dial and sent it to them. The reported times were off by more than 30 minutes! With much effort I finally got some readings to agree only if I accepted that the surveyor was off by 9 degrees! I suspect that the building contractor may have used a magnetic compass or was merely reading construction plans. The result is if I do this again I would have the client use the board method even if they claim to have a reliable surveyor - the sun is the best surveyor. I would send a board with a perpendicular attached. On the board would be a bubble level and a digital watch. Have the client draw along the shadow of the perpendicular while holding the board level against the wall. Then note the time to the second. Have them repeat this at several intervals at least hours apart and at different locations along the wall. When they return everything you have the shadows you can measure. You can also check the time on the digital watch. Claude Hartman 35.13 N 120.58 W Even with the best of -
Wall Declination Through the Window
Hello Fellow Dialists, I posted this note last spring. since the subject came up again, i though I would re-post it. I have used the technique several times since the posting and it has worked well. I have had clients take the readings and send me the data for reduction. Even these resdings have been within half a degree. I will re-post the cautionary notes as well. Roger Bailey Vertical declining dials like those that decorate houses in the alpine villages of Europe are my favourite style of sundial to design and build. With programs like Fer de Vries' Zonwvlak or Francois Blateyron's Shadows, the difficult mathematics are easily solved to produce the basic design for a dial for any wall declination. The problem in such a design is to accurately measure the declination of the wall. Compass measurements are inaccurate. Plumb bob or nail shadow measurements work but are awkward to do correctly. The math to solve for solar azimuth is also intimidating. I faced this problem recently when I designed a dial as a gift for my sister-in-law who lives on the other side of the country (and Canada is a large country). On a short visit I had to get the appropriate measurements without anyone suspecting what I was doing. The usual tools like step ladders supporting plumb bobs, carpenters' squares etc were unavailable. The solution was simple. Measure the azimuth of the sun through the window! The windows in well built modern houses (an oxymoron) are vertically set in the plane of the wall. The shadow of the window frame on a pad of paper held horizontally, with one edge pressed on the glass determines the azimuth of the sun with respect to the plane of the window at that instant. All you need to do is mark the shadow line on the paper and the exact time. Take several readings, hours apart, for better accuracy and a check on measurements. To keep the orientation correct, I also note the rough heading of north and add to the shadow line an arrow pointing to the sun. Data reduction is still a problem. You have to correct for clock error, know the latitude, longitude, equation of time and declination of the sun and solve the usual spherical trigonometry equations to determine the azimuth of the sun. This is greatly simplified using The Dialist's Companion a program written by Terwilliger and Sawyer and published by NASS. Enter the appropriate data; the program solves for azimuth. From that calculated azimuth compared to the measured azimuth, the declination of the window (wall) is determined by simple geometry. The technique works very well. I have used it many times with excellent results. Generally the declination results agree to within half a degree. Errors are obvious as outliers. My sister-in-law was surprised by the gift and amazed by the accuracy of a dial designed and built thousands of miles from it's unique location. If you are interested, e-mail me and I will send pictures (106 kb JPG) and operating instructions for the dial. Cheers, Roger Bailey Walking Shadow Designs Canmore, Alberta, Canada
Re: Wall Declination
Dear Roger, Thank you for posting the directions for finding azimuth. I have found the Dialist's Companion equally valuable for some of the same purposes as you describe. Your explanation brings to mind how it would be possible to make an azimuthal dial for a window seal. The use of Zevonplot from Fer de Vries makes it very easy. Sincerely, Warren Thom Roger Bailey wrote: Hello Fellow Dialists, The solution was simple. Measure the azimuth of the sun through the window! The windows in well built modern houses (an oxymoron) are vertically set in the plane of the wall. The shadow of the window frame on a pad of paper held horizontally, with one edge pressed on the glass determines the azimuth of the sun with respect to the plane of the window at that instant. All you need to do is mark the shadow line on the paper and the exact time. Take several readings, hours apart, for better accuracy and a check on measurements. To keep the orientation correct, I also note the rough heading of north and add to the shadow line an arrow pointing to the sun. Data reduction is still a problem. You have to correct for clock error, know the latitude, longitude, equation of time and declination of the sun and solve the usual spherical trigonometry equations to determine the azimuth of the sun. This is greatly simplified using The Dialist's Companion a program written by Terwilliger and Sawyer and published by NASS. Enter the appropriate data; the program solves for azimuth. From that calculated azimuth compared to the measured azimuth, the declination of the window (wall) is determined by simple geometry. The technique works very well. I have used it many times with excellent results. Generally the declination results agree to within half a degree. Errors are obvious as outliers. Cheers, Roger Bailey Walking Shadow Designs Canmore, Alberta, Canada
Re: Wall Declination
25 Apr 98 Hello Rodger, You wrote: (snip) The problem in such a design is to accurately measure the declination of the wall. Compass measurements are inaccurate. Plumb bob or nail shadow measurements work but are awkward to do correctly. The math to solve for solar azimuth is also intimidating. I faced this problem recently when I designed a dial as a gift for my sister-in-law who lives on the other side of the country (and Canada is a large country). On a short visit I had to get the appropriate measurements without anyone suspecting what I was doing. The usual tools like step ladders supporting plumb bobs, carpenters' squares etc were unavailable. The solution was simple. Measure the azimuth of the sun through the window! (snip) Thanks for sharing this neat way of determining the declination of a wall. Your process has a lot to recommend it over the method I normally use, which involves a plumb bob and carpenter's square. I particularly like the idea that your method may be exercised covertly. Also, indoors out of the [cold] wind sounds just fine! All the best, Mac Oglesby P.S. My sister-in-law was surprised by the gift and amazed by the accuracy of a dial designed and built thousands of miles from it's unique location. If you are interested, e-mail me and I will send pictures (106 kb JPG) and operating instructions for the dial. I've seen photos of two of Roger's beautiful dials and strongly recommend that others request his pictures.
