Re: [Qgis-user] split polygon with lines seems not working correctly

[David Greenewalt]

Luigi,

The lines must fully transect the polygon in order to split.  The dotted 
lines in the image are examples of such lines.


Hope this helps,
David


On 6/10/2020 11:31 AM, Luigi Raffaele Sapone wrote:


Hello

I’m using QGIS 3.12

I have a poly shapefile named building.shp in the zip file, and a line 
shapefile, named line.shp.


I’m using the geoprocessing function ‘split polygon by line’ using 
poly.shp as input, and line.shp as divide layer.


I obtain the ‘split_by_line.shp’. But, in this splitted file, the 
polygon was not divided considering all the lines present, but only 
some of them, as visible in ‘split_by_line.shp’.


Is there something wrong?

Regards


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Re: [Qgis-user] split polygon with lines seems not working correctly

[David Greenewalt]

Luigi,

I see the problem now, I would suggest:

1. Polygons to Lines (on the Buildings layer)

2. Merge vector Layers (lines-from-buildings, and line layer)

3. Polygonize (merged layer)

4. Join Attributes from Location (New polygons, building layer) 
(Geometric predicate = within)


David


On 6/10/2020 11:31 AM, Luigi Raffaele Sapone wrote:


Hello

I’m using QGIS 3.12

I have a poly shapefile named building.shp in the zip file, and a line 
shapefile, named line.shp.


I’m using the geoprocessing function ‘split polygon by line’ using 
poly.shp as input, and line.shp as divide layer.


I obtain the ‘split_by_line.shp’. But, in this splitted file, the 
polygon was not divided considering all the lines present, but only 
some of them, as visible in ‘split_by_line.shp’.


Is there something wrong?

Regards


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Re: [Qgis-user] colorramp starting from white

[David Greenewalt]

The ramps that go from white to color (just 2 colors - for example 
white/green) have more stops than needed. I would just delete the 
intermediate stops and set the first to the pale green of your choice.  
Then save your new color ramp for future use.


For maximum contrast between high and low data values, you could leave 
it as white/green and then set the screen/page background color to 
something other than the default white.  Go to Project-Properties and 
then Background Color.


David



On 6/15/2020 10:50 AM, Seggie, Graeme wrote:

Would adapting and using this code help at all?

https://gis.stackexchange.com/questions/134435/what-is-replacement-for-setcolorshadingalgorithm-in-qgis-2-6/134589#134589

Graeme



-Original Message-
From: Qgis-user  On Behalf Of Raymond Nijssen
Sent: 15 June 2020 15:34
To: DelazJ 
Cc: qgis-user 
Subject: Re: [Qgis-user] colorramp starting from white

Attached is an example image.

Currently it is very hard to distinguish lakes from areas in the lowest class, 
for example in the southwest area.

In the map at the right, I manually adjusted the color ramp to start at a light 
green color. Should that be the default?

Raymond



On 15-06-2020 16:04, DelazJ wrote:

Hi Raymond,

Instead of changing manually, why not "Invert the Color ramp" when
applying it?
https://docs.qgis.org/testing/en/docs/user_manual/introduction/general
_tools.html#the-color-ramp-drop-down-shortcut

Regards,
Harrissou

Le lun. 15 juin 2020 à 15:53, Raymond Nijssen mailto:r.nijs...@terglobo.nl>> a écrit :

 Am I the only one who would like the color ramps in QGIS to NOT start
 from (super nearly) white, but from a light version of the color?

 For example, "Reds" should go from (light) pink to red.

 Currently, the first class in my legend always looks white, as many
 other parts of my map often do. Therefore it is hard to see where my
 data is and where not.

 Another thing, changing it manually is hard because of the 7 stops in
 the ramps.

 I'm happy to figure this out and make a PR, but would like to know
 other's opinions first.

 Regards,
 Raymond


 --
 Terglobo
 Fahrenheitstraat 1
 5223 BJ 's-Hertogenbosch
 The Netherlands
 +31 (0) 6 25 31 49 83
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Re: [Qgis-user] Field Calculator Expression

[David Greenewalt]

You could try a "CASE" expression:


expression CASE

CASEWHEN conditionTHEN result[ …n ][ ELSE result]END

[ ] marks optional components

Arguments


WHEN condition- The condition expression to evaluate.

THEN result- If conditionevaluates to True then resultis evaluated and 
returned.


ELSE result- If none of the above conditions evaluated to True then 
resultis evaluated and returned.


Example

CASEWHEN "ID" = 1 THEN 'Yellow'
WHEN "ID" = 2 THEN 'Green'END


Hope this helps,
David


On 8/17/2020 7:20 PM, krishna Ayyala wrote:

I have the following attribute table with two fields ID and ID2
image.png

What expression can I use within the field calculator so that, I can 
fill the values for ID2 as below?


ID  ID2
1   Yellow
2   Green
3   White
4   Blue
5   Orange
6   Brown
7   Light Blue
8   Light Yellow
9   Light Green





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Re: [Qgis-user] automatic data entry

[David Greenewalt]

I typed "closest" into the search box (bottom left of screen), and saw 
the processing algorithm  "Join Attributes By Nearest" .  It may be 
worth looking into.


Thanks,
David



On 9/17/2020 7:07 AM, Nicolas Cadieux wrote:

Hi,
You could make a 25m buffer and then use “join attributes by location” 
fond in processing.




Once the information is in the buffer object table, start again with 
the buffer and your line, point and polygons.


https://www.qgistutorials.com/en/docs/performing_spatial_queries.html?highlight=buffer

https://www.qgistutorials.com/en/docs/3/performing_spatial_joins.html


Nicolas Cadieux


Le 17 sept. 2020 à 04:23, FVHGmail  a écrit :



Hello ,

I use QGIS 3.14  and I want to arrange when I draw a line , point or 
area that the fields  City and Street can be are filled with the 
closest  City and Street-name out of OpenStreetMap .   In a range of 
25 Meter  . The marking I draw are always on a street or bicycle path.


Maybe an easy question but I am new in the use of QGIS  so I can use 
a little help the experts .


Kind regards

Ferrol

Sent from Mail  for 
Windows 10


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Re: [Qgis-user] How do I clean up this geometry?

[David Greenewalt]

I notice that the small polygon is a separate park. You could delete the 
polygon. (or leave it as the separate area).   If the polys are to be 
merged, you could manually edit the boundary (pull the vertices) so they 
overlap completely, and then merge the polys.


If v.clean doesn't address all the problems and there are too many, you 
could build the polys from lines. If the lines are correct, the polys 
created from them will be clean.


David




On 1/8/2021 3:28 PM, qgis-u...@stripfamily.net wrote:
This linked 
 
file, proclaimed.zip, is the boundary of the Santa Fe National Forest 
as supplied by the USFS.

If you focus on this area




There is some problematic geometry. If I do a dissolve I get this:



If I remove the holes, I'm left with this bit of stray boundary:


I then remove that with edit nodes. But the resulting polygon is still 
not clean  - if I try to use the field calculator to add the area 
(using $area), I get /null.

/There is bad geometry that I'm not spotting, but how do I find it?


The second linked 
file, 
clean.zip, is the result of the steps above.





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Re: [Qgis-user] how to find center of polygons and/or major and minor diameters

[David Greenewalt]

Azzurra,


Two other methods to try are:


Point on surface

Pole of inaccessibility


Both found in the Processing Toolbox


David


On 1/12/2021 2:13 PM, Brent Wood wrote:
This may be a suitable approach, not specifically the ellipse axis 
approach, but:



Vector -> Geometry tools -> Centroid

may do what you want, depending on exactly how QGIS calculates the 
centroid...




Brent Wood

Principal Technician, Fisheries
NIWA
DDI:  +64 (4) 3860529


*From:* Qgis-user  on behalf of 
Azzurra Lentini 

*Sent:* Wednesday, January 13, 2021 08:04
*To:* qgis-user 
*Subject:* [Qgis-user] how to find center of polygons and/or major and 
minor diameters
Hi to all, any suggestion on how to quickly draw the minor and major 
diameters of different polygons? I have a shapefile of polygons: some 
of the polygons are ellipses and others are similar to ellipses but 
not regular.
My aim is to find the center of these polygons (In this aim I was 
thinking to draw the 2 diameters and to use the intersection of these 
diameters as a center point of the polygon)

Thanks, Azzurra
--
Lecturer GIS University "Roma Tre"
Consultant Environmental Risk Prevention and Hydrogeology
AZZURRA LENTINI
++
Italy Mobile Tel.: **(39) 338 24 40 676
++
SKYPE azzurrahydro
++

*_azzurralent...@gmail.com _*

*_azzurra.lent...@uniroma3.it  _**__*

++
*Par respect pour l'environnement,*

*n'imprimez ce mail qu'en cas d'absolue nécessité*





  Brent Wood
Principal Technician - GIS and Spatial Data Management
Programme Leader - Environmental Information Delivery
+64-4-386-0529 |
National Institute of Water & Atmospheric Research Ltd (NIWA)
301 Evans Bay Parade Hataitai Wellington New Zealand
*Connect with NIWA:* niwa.co.nz  Facebook 
 LinkedIn 
 Twitter 
 Instagram 



To ensure compliance with legal requirements and to maintain cyber 
security standards, NIWA's IT systems are subject to ongoing 
monitoring, activity logging and auditing. This monitoring and 
auditing service may be provided by third parties. Such third parties 
can access information transmitted to, processed by and stored on 
NIWA's IT systems


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Re: [Qgis-user] Map styles changing when I export as image

[David Greenewalt]

Jeremy,

What version of QGIS are you using?  It may be entirely unrelated, but I 
ran into serious problems exporting map layouts to PDF.  I noticed it at 
3.18 (Windows 10).  Some, not all, exports were using a lot of memory, 
and it would actually cause one of my duel screens to go blank and stop 
working.  Apparently I had too little RAM (8 gigs) - I added 16 more and 
all is working fine now.  It took a long time to resolve as I was 
looking at software and settings and it was actually my hardware/system 
being overwhelmed.  Just a thought.


David



On 3/21/2021 4:47 AM, jeremy benwell wrote:

Hi all,
I'm having some trouble with exporting my map as an image. When I try 
to export my map as an image all the styles change (see images below, 
I had to shrink size to make email within 100kb limit so they are a 
bit blurry). The dpi I choose is 100. I'm guessing the problem has 
something to do with what layers are selected in the project tab but 
can't seem to figure out how exactly. Is there some way to stop the 
project tab from feeding information to the print layout tab so i can 
export the print layout tab as an image exactly as is.


Any help would be much appreciated.

Cheers,

Jeremy

How I want my map to be exported as an image
imgonline-com-ua-CompressToSize-uIfjmSKXaLw1ocp.jpg

My project layers
imgonline-com-ua-CompressToSize-tRIxoZUAwx6sH.jpg


How my map is actually exported as an image
imgonline-com-ua-CompressToSize-VePdVaL4aS.jpg



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Re: [Qgis-user] First steps with 3D Scan Data?

[David Greenewalt]

I know nothing of the data you have or the subject in general, but was 
intrigued a few years ago with software that would generate 3d models 
from photos ("scans from all angles"?).  Look at 
https://www.agisoft.com/features/standard-edition/ for example. May not 
be helpful or fruitful, but fun (and pretty incredible).


Good Luck,
David


On 3/25/2021 5:07 PM, Bernd Vogelgesang wrote:

Hi folks,

in a project on a former dumpside now to be transformed into a sand
lizard habitat, I saw the chance to get my hands dirty for the first
time on 3D scan data (terrestrial). I received 10GB of stuff, and now
I'm completely lost.

The data consists of .rwcx files, .tzf files and lots of other stuff.

Is there any chance that I can process any of this data with an open
source stack?
Or what should be done, to make them digestible?

Second step: There seem to be 32 different scans of the area form all
angles. In case I succeed to somehow load the data, how do I combine 
them ?


For the first steps, I actually "only" would like to generate a decent
DEM from the data to be able to place some features on a map for the
guys in charge to do the habitat stuff.

Any kind of hints or links to reads about this topic would be appreciated

Cheers,

Bernd


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Re: [Qgis-user] Fw: Did scale change outputting to PDF?

[David Greenewalt]

John,

Is it possible to ask Kinkos what scale they printed the base maps?  
They don't have to actually reprint the maps, just go through the 
motions.  Open the PDF and look at the print options. As Andreas points 
out, the default is often "Fit" and there will be a "zoom" or "scale" 
percent displayed in the application (I use Foxit, and Adobe and both 
show this).  The page size parcel maps will have to be printed at this 
scale.  If they can guarantee that the print scale was 100%, then I 
would assume some other export discrepancy.


David


On 5/27/2021 4:15 AM, Andreas Neumann wrote:


Hi John,

No - the PDF export does not distort the scale. But the printing of 
the PDF file might.


It is absolutely important that - when printing the PDF - the setting 
"Actual size" or "Custom Scale at 100%" is used. All other options 
will change the scale.


As far as I know, the default option when printing is "Fit", which 
will often shrink the content by some percentage - because some often 
"invisible" or white background might be present in the file that 
extends right to the edge of the page format. Acrobat then thinks that 
the content goes beyond the "printable area" of the printer and will 
scale down the whole file.


Hope that clarifies this potential pit-fall when printing PDF files. 
It might well be a different issue than the one I describe, but this 
is a very common source of error that I know.


Andreas

On 2021-05-27 10:02, John Antkowiak wrote:

Hi, Jochen. Your suggestion sounds do-able; I'll play around with it 
and see if I can sort it out. I've got some digital calipers around 
here somewhere :)
What I'm hearing is that the process of converting both the base map 
(and yes, I did create it in QGIS) and the parcel maps into PDF will 
distort the scale. (And that a print shop might compound the problem 
by manually fitting the source file to the printable area. Yes?) A 
question then is why didn't the PDF conversion distort them all the 
same way, to the same degree? The base maps are done now and I 
couldn't afford to do them again no matter what, so they are what 
they are. Going forward, is there an export option in Print Layout 
that will not distort the scale of the parcel maps?

I am so relieved that someone has an explanation for this!
- John A.
- Forwarded Message -
*From:* j.hu...@post-ist-da.de 
*To:* "qgis-user@lists.osgeo.org" 
*Sent:* Thursday, May 27, 2021, 03:33:12 AM EDT
*Subject:* Re: [Qgis-user] Did scale change outputting to PDF?
Hi John,
as I understand it, you created the base map in QGIS. If you use the 
measure tool in QGIS to get the distance between two distinct 
features in the map (e.g. road intersections) and then measure the 
same distance on the printed base map with a ruler, it should be 
possible to calculate the scale. Maybe use two distances, one aligned 
more or less horizontally and one vertically, to check if the scaling 
is proportional.
As Andreas pointed out, it is probably a problem with the settings 
when the PDF was printed. In my experience it is a good idea to go to 
print shops usually working for architects and engineers since they 
are familiar with the importance of scaling (for advertising etc. it 
is more important that the whole content is printed, so that scaling 
might be used to fit the output to the printable area without 
potential cropping).
You can print directly to a plotter in QGIS if you have access to the 
device, avoiding the PDF detour.

EPSG 2264 should be fine. Units should be US feet.
Regards
Jochen
Am 27.05.21 um 07:15 schrieb John Antkowiak:
Hi. This plan was too simple to fail - but it failed. The charity 
whose project this is needed a large (that is... massive) paper wall 
map on which to plot and rethink its delivery driver assignments. 
Both drivers and delivery addresses are subject to change from week 
to week but it's not a pizza delivery; this is a regular run to 
supply people in a bad way. So the plan was to print the base map 
(roads and road names and county boundaries only) and then print 8.5 
x 11 address maps with parcel data and orthos. That way, the base 
maps don't change but the physical parcel layer is flexible. (On top 
of that is a third paper layer indicating which drivers go where so 
someone can stand back and take in the whole picture graphically. 
Not a cutting-edge state of the digital art solution, but not 
everyone is cut out for that. It is what it is.) In order for this 
to work, the parcel maps have to be the same scale as the base map. 
Which they were... in QGIS.
We have to convert all the maps to PDF to print them, and we had to 
send the base map PDFs to FedEx/Kinkos to print the 9 map grid 
panels at 42" by 62" each.
When we got the big base maps up on the wall, we discovered the 
scale did not match the 8.5" x 11" parcel maps output to PDF and 
printed from home. It's not off by a lot, but it's enough to be 
painfully obvious from a single standard size sheet of paper. I 
d

Re: [Qgis-user] Changing default pop-up attribute when using Identify tool

[David Greenewalt]

Double click on the layer to bring up layer properties, then find the 
tab for "Display".  At the top of the window is a field selection list.  
This will set the value to display at the top of the identify window.  
Hope this is what you're looking for.


David



On 12/8/2021 3:01 PM, Holly McLachlan wrote:
Is there a simple way to change the attribute table record that is 
automatically displayed in the right side pop-up panel when using the 
identify tool. I'm trying to single out a point feature in a point 
shapefile with a large set of attributes. I want to see only one 
associated row from the attribute table -- one that displays soil Li 
values in ppms. Currently the panel that pop ups on the right side of 
the map viewer shows these data under the "Action" sub-tree, but only 
for another row (record). I need to change the default record that is 
called by this tool.


Thank you,

--
Holly S Mclachlan
(775) 762-3408

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