Re: Stus-List Electronic navigation - chartplotters
I suspect that you are correct, Dennis. If you look at the legend of a paper chart, it will tell you when the cartographic data was recorded. The last section of the ICW in North Carolina was dug in the mid 30’s, and much of the survey data was collected between the 1930s and the 1950s – when accuracy was far below the plus or minus 10 feet you can get with modern GPS. There are sections around here where a boat in mid-channel will show to be 100 feet or more off to one side and on dry land. Segments that are regularly dredged or where markers have been moved in the past few years will have much more accurate cartographic data. The age and accuracy of the survey data is one of the reasons why NOAA no longer prints the “Magenta Line” on current ICW charts. Another potential inaccuracy, somewhat spotty, is an actual proof that Einstein was correct in general relativity. The geosynchronous GPS constellation is has a velocity somewhat greater than that of the point below it on the Earth’s surface. General Relativity predicts that time moves more slowly as velocity increases. Consequently the clocks on the satellites get reset by a few milliseconds every couple of hours to match the official atomic clock. There was an article in a science magazine about the GPS system a few years ago, and the writer mentioned that on the day he visited the GPS system control center in Colorado there was a communication issue between the atomic clock and the control center for several hours – with the result that the GPS in the reporter’s car directed him to a spot more than ½ mile away from the GPS control location. That’s why a prudent mariner uses multiple sources of navigation information – and why you need to keep your head out of the boat. Rick Brass Washington, NC From: CnC-List [mailto:cnc-list-boun...@cnc-list.com] On Behalf Of Dennis C. via CnC-List Sent: Tuesday, December 18, 2018 1:42 PM To: CnClist Cc: Dennis C. Subject: Re: Stus-List Electronic navigation - chartplotters The positions were accurate during the rest of the 178 nm trip except in that short section of the ICW. My guess is the cartography was inaccurate there. Dennis C. On Tue, Dec 18, 2018 at 12:34 PM Jerome Tauber via CnC-List mailto:cnc-list@cnc-list.com> > wrote: Is your GPS set to output positions using the corrrect Geodetic Datum? Jerry -Original Message- From: Dennis C. via CnC-List mailto:cnc-list@cnc-list.com> > To: CnClist mailto:CnC-List@cnc-list.com> > Cc: Dennis C. mailto:capt...@gmail.com> > Sent: Tue, Dec 18, 2018 11:22 am Subject: Stus-List Electronic navigation - chartplotters Over the weekend I brought Touche' back home to Mandeville for the winter. Nice trip but a bit cold for my Southern blood. Here's something I observed. For those who rely exclusively on charplotters and electronic navigation, here's something you need to look at. Go to Google Earth and enter the following in the search window: 30°18'2.24"N 87°37'34.10"W That will take you to a marshy island in Portage Creek, a portion of the ICW near Orange Beach, AL. That's where the GPS chartplotter showed the boat symbol representing Touche' was when Touche' was actually in the middle of the channel adjacent to island. If I had been using the boat symbol for navigation and had been steering to keep the symbol mid-channel, Touche' would have been in the trees on the south bank of the ICW. The GPS continued to show Touche' in the trees on the north bank during the entire transit of this section of the ICW. Having navigated these waters dozens of times, I'm very familiar with them but a boater transiting here the first time in heavy fog Once out of the man-made ICW the GPS returned to being fairly accurate. Just saying, once again, how important it is to use your eyeballs and not rely on electronics exclusively for navigation. Maybe it doesn't seem like a big deal when you're in a channel that is well marked but there are lots of areas with no marks, no land and seriously shallow shoals or rocks. Dennis C. Touche' 35-1 #83 Mandeville, LA ___ Thanks everyone for supporting this list with your contributions. Each and every one is greatly appreciated. If you want to support the list - use PayPal to send contribution -- https://www.paypal.me/stumurray ___ Thanks everyone for supporting this list with your contributions. Each and every one is greatly appreciated. If you want to support the list - use PayPal to send contribution -- https://www.paypal.me/stumurray ___ Thanks everyone for supporting this list with your contributions. Each and every one is greatly appreciated. If you want to support the list - use PayPal to send contr
Re: Stus-List Electronic navigation - chartplotters
Poor satellite coverage will drop accuracy too. It’s a factor in land surveying in planning hours of data collection. Bill Dakin > On Dec 18, 2018, at 12:41 PM, Dennis C. via CnC-List > wrote: > > The positions were accurate during the rest of the 178 > ___ Thanks everyone for supporting this list with your contributions. Each and every one is greatly appreciated. If you want to support the list - use PayPal to send contribution -- https://www.paypal.me/stumurray
Re: Stus-List Electronic navigation - chartplotters
Dennis. Good guess but where else. Lot water on the surface of the earth On Tue, Dec 18, 2018 at 3:46 PM Bruce Pope via CnC-List < cnc-list@cnc-list.com> wrote: > Thanks Dennis. > Couldn't agree more. I love this quote from NOAA Office of Coast Survey: > "The age and accuracy of data on nautical charts can vary. Depth > information on nautical charts, paper or digital, is based on data from the > latest available hydrographic survey, which in many cases may be quite old. > In too many cases, the data is more than 150 years old. Sometimes, > particularly in Alaska, the depth measurements are so old that they may > have originated from Captain Cook in 1778." > My favorite - sailing directions for the south-west coast of Barbuda > indicate the deepest water is relatively tight to shore. We were > paralleling the beach about 150m off and for about 20 minutes the chart > plotter showed our position as driving down a road that runs just inland of > the beach. > > -- > *From:* Dennis C. > *Sent:* Tuesday, December 18, 2018 9:21 AM > *To:* CnClist > > *Subject:* Stus-List Electronic navigation - chartplotters > > Over the weekend I brought Touche' back home to Mandeville for the > winter. Nice trip but a bit cold for my Southern blood. Here's something > I observed. > > For those who rely exclusively on charplotters and electronic navigation, > here's something you need to look at. Go to Google Earth and enter the > following in the search window: 30°18'2.24"N 87°37'34.10"W > > That will take you to a marshy island in Portage Creek, a portion of the > ICW near Orange Beach, AL. That's where the GPS chartplotter showed the > boat symbol representing Touche' was when Touche' was actually in the > middle of the channel adjacent to island. If I had been using the boat > symbol for navigation and had been steering to keep the symbol mid-channel, > Touche' would have been in the trees on the south bank of the ICW. > > The GPS continued to show Touche' in the trees on the north bank during > the entire transit of this section of the ICW. Having navigated these > waters dozens of times, I'm very familiar with them but a boater transiting > here the first time in heavy fog > > Once out of the man-made ICW the GPS returned to being fairly accurate. > > Just saying, once again, how important it is to use your eyeballs and not > rely on electronics exclusively for navigation. Maybe it doesn't seem like > a big deal when you're in a channel that is well marked but there are lots > of areas with no marks, no land and seriously shallow shoals or rocks. > > Dennis C. > Touche' 35-1 #83 > Mandeville, LA > > > ___ > > Thanks everyone for supporting this list with your contributions. Each > and every one is greatly appreciated. If you want to support the list - > use PayPal to send contribution -- https://www.paypal.me/stumurray > > -- Sent from Gmail Mobile ___ Thanks everyone for supporting this list with your contributions. Each and every one is greatly appreciated. If you want to support the list - use PayPal to send contribution -- https://www.paypal.me/stumurray
Re: Stus-List Electronic navigation - chartplotters
Thanks Dennis. Couldn't agree more. I love this quote from NOAA Office of Coast Survey: "The age and accuracy of data on nautical charts can vary. Depth information on nautical charts, paper or digital, is based on data from the latest available hydrographic survey, which in many cases may be quite old. In too many cases, the data is more than 150 years old. Sometimes, particularly in Alaska, the depth measurements are so old that they may have originated from Captain Cook in 1778." My favorite - sailing directions for the south-west coast of Barbuda indicate the deepest water is relatively tight to shore. We were paralleling the beach about 150m off and for about 20 minutes the chart plotter showed our position as driving down a road that runs just inland of the beach. From: Dennis C. Sent: Tuesday, December 18, 2018 9:21 AM To: CnClist Subject: Stus-List Electronic navigation - chartplotters Over the weekend I brought Touche' back home to Mandeville for the winter. Nice trip but a bit cold for my Southern blood. Here's something I observed. For those who rely exclusively on charplotters and electronic navigation, here's something you need to look at. Go to Google Earth and enter the following in the search window: 30°18'2.24"N 87°37'34.10"W That will take you to a marshy island in Portage Creek, a portion of the ICW near Orange Beach, AL. That's where the GPS chartplotter showed the boat symbol representing Touche' was when Touche' was actually in the middle of the channel adjacent to island. If I had been using the boat symbol for navigation and had been steering to keep the symbol mid-channel, Touche' would have been in the trees on the south bank of the ICW. The GPS continued to show Touche' in the trees on the north bank during the entire transit of this section of the ICW. Having navigated these waters dozens of times, I'm very familiar with them but a boater transiting here the first time in heavy fog Once out of the man-made ICW the GPS returned to being fairly accurate. Just saying, once again, how important it is to use your eyeballs and not rely on electronics exclusively for navigation. Maybe it doesn't seem like a big deal when you're in a channel that is well marked but there are lots of areas with no marks, no land and seriously shallow shoals or rocks. Dennis C. Touche' 35-1 #83 Mandeville, LA ___ Thanks everyone for supporting this list with your contributions. Each and every one is greatly appreciated. If you want to support the list - use PayPal to send contribution -- https://www.paypal.me/stumurray
Re: Stus-List Electronic navigation - chartplotters
The positions were accurate during the rest of the 178 nm trip except in that short section of the ICW. My guess is the cartography was inaccurate there. Dennis C. On Tue, Dec 18, 2018 at 12:34 PM Jerome Tauber via CnC-List < cnc-list@cnc-list.com> wrote: > Is your GPS *set* to output positions using the corrrect *Geodetic* > Datum? Jerry > > > > -Original Message- > From: Dennis C. via CnC-List > To: CnClist > Cc: Dennis C. > Sent: Tue, Dec 18, 2018 11:22 am > Subject: Stus-List Electronic navigation - chartplotters > > Over the weekend I brought Touche' back home to Mandeville for the > winter. Nice trip but a bit cold for my Southern blood. Here's something > I observed. > > For those who rely exclusively on charplotters and electronic navigation, > here's something you need to look at. Go to Google Earth and enter the > following in the search window: 30°18'2.24"N 87°37'34.10"W > > That will take you to a marshy island in Portage Creek, a portion of the > ICW near Orange Beach, AL. That's where the GPS chartplotter showed the > boat symbol representing Touche' was when Touche' was actually in the > middle of the channel adjacent to island. If I had been using the boat > symbol for navigation and had been steering to keep the symbol mid-channel, > Touche' would have been in the trees on the south bank of the ICW. > > The GPS continued to show Touche' in the trees on the north bank during > the entire transit of this section of the ICW. Having navigated these > waters dozens of times, I'm very familiar with them but a boater transiting > here the first time in heavy fog > > Once out of the man-made ICW the GPS returned to being fairly accurate. > > Just saying, once again, how important it is to use your eyeballs and not > rely on electronics exclusively for navigation. Maybe it doesn't seem like > a big deal when you're in a channel that is well marked but there are lots > of areas with no marks, no land and seriously shallow shoals or rocks. > > Dennis C. > Touche' 35-1 #83 > Mandeville, LA > > > ___ > > Thanks everyone for supporting this list with your contributions. Each > and every one is greatly appreciated. If you want to support the list - > use PayPal to send contribution -- https://www.paypal.me/stumurray > > ___ > > Thanks everyone for supporting this list with your contributions. Each > and every one is greatly appreciated. If you want to support the list - > use PayPal to send contribution -- https://www.paypal.me/stumurray > > ___ Thanks everyone for supporting this list with your contributions. Each and every one is greatly appreciated. If you want to support the list - use PayPal to send contribution -- https://www.paypal.me/stumurray
Re: Stus-List Electronic navigation - chartplotters
Is your GPS set to output positions using the corrrect Geodetic Datum? Jerry -Original Message- From: Dennis C. via CnC-List To: CnClist Cc: Dennis C. Sent: Tue, Dec 18, 2018 11:22 am Subject: Stus-List Electronic navigation - chartplotters Over the weekend I brought Touche' back home to Mandeville for the winter. Nice trip but a bit cold for my Southern blood. Here's something I observed. For those who rely exclusively on charplotters and electronic navigation, here's something you need to look at. Go to Google Earth and enter the following in the search window: 30°18'2.24"N 87°37'34.10"W That will take you to a marshy island in Portage Creek, a portion of the ICW near Orange Beach, AL. That's where the GPS chartplotter showed the boat symbol representing Touche' was when Touche' was actually in the middle of the channel adjacent to island. If I had been using the boat symbol for navigation and had been steering to keep the symbol mid-channel, Touche' would have been in the trees on the south bank of the ICW. The GPS continued to show Touche' in the trees on the north bank during the entire transit of this section of the ICW. Having navigated these waters dozens of times, I'm very familiar with them but a boater transiting here the first time in heavy fog Once out of the man-made ICW the GPS returned to being fairly accurate. Just saying, once again, how important it is to use your eyeballs and not rely on electronics exclusively for navigation. Maybe it doesn't seem like a big deal when you're in a channel that is well marked but there are lots of areas with no marks, no land and seriously shallow shoals or rocks. Dennis C.Touche' 35-1 #83Mandeville, LA ___ Thanks everyone for supporting this list with your contributions. Each and every one is greatly appreciated. If you want to support the list - use PayPal to send contribution -- https://www.paypal.me/stumurray ___ Thanks everyone for supporting this list with your contributions. Each and every one is greatly appreciated. If you want to support the list - use PayPal to send contribution -- https://www.paypal.me/stumurray
Re: Stus-List Electronic navigation - chartplotters
I think that’s why electronics are called navigational aids On Tue, Dec 18, 2018 at 12:22 PM Dennis C. via CnC-List < cnc-list@cnc-list.com> wrote: > Over the weekend I brought Touche' back home to Mandeville for the > winter. Nice trip but a bit cold for my Southern blood. Here's something > I observed. > > For those who rely exclusively on charplotters and electronic navigation, > here's something you need to look at. Go to Google Earth and enter the > following in the search window: 30°18'2.24"N 87°37'34.10"W > > That will take you to a marshy island in Portage Creek, a portion of the > ICW near Orange Beach, AL. That's where the GPS chartplotter showed the > boat symbol representing Touche' was when Touche' was actually in the > middle of the channel adjacent to island. If I had been using the boat > symbol for navigation and had been steering to keep the symbol mid-channel, > Touche' would have been in the trees on the south bank of the ICW. > > The GPS continued to show Touche' in the trees on the north bank during > the entire transit of this section of the ICW. Having navigated these > waters dozens of times, I'm very familiar with them but a boater transiting > here the first time in heavy fog > > Once out of the man-made ICW the GPS returned to being fairly accurate. > > Just saying, once again, how important it is to use your eyeballs and not > rely on electronics exclusively for navigation. Maybe it doesn't seem like > a big deal when you're in a channel that is well marked but there are lots > of areas with no marks, no land and seriously shallow shoals or rocks. > > Dennis C. > Touche' 35-1 #83 > Mandeville, LA > > > ___ > > Thanks everyone for supporting this list with your contributions. Each > and every one is greatly appreciated. If you want to support the list - > use PayPal to send contribution -- https://www.paypal.me/stumurray > > -- Sent from Gmail Mobile ___ Thanks everyone for supporting this list with your contributions. Each and every one is greatly appreciated. If you want to support the list - use PayPal to send contribution -- https://www.paypal.me/stumurray
Stus-List Electronic navigation - chartplotters
Over the weekend I brought Touche' back home to Mandeville for the winter. Nice trip but a bit cold for my Southern blood. Here's something I observed. For those who rely exclusively on charplotters and electronic navigation, here's something you need to look at. Go to Google Earth and enter the following in the search window: 30°18'2.24"N 87°37'34.10"W That will take you to a marshy island in Portage Creek, a portion of the ICW near Orange Beach, AL. That's where the GPS chartplotter showed the boat symbol representing Touche' was when Touche' was actually in the middle of the channel adjacent to island. If I had been using the boat symbol for navigation and had been steering to keep the symbol mid-channel, Touche' would have been in the trees on the south bank of the ICW. The GPS continued to show Touche' in the trees on the north bank during the entire transit of this section of the ICW. Having navigated these waters dozens of times, I'm very familiar with them but a boater transiting here the first time in heavy fog Once out of the man-made ICW the GPS returned to being fairly accurate. Just saying, once again, how important it is to use your eyeballs and not rely on electronics exclusively for navigation. Maybe it doesn't seem like a big deal when you're in a channel that is well marked but there are lots of areas with no marks, no land and seriously shallow shoals or rocks. Dennis C. Touche' 35-1 #83 Mandeville, LA ___ Thanks everyone for supporting this list with your contributions. Each and every one is greatly appreciated. If you want to support the list - use PayPal to send contribution -- https://www.paypal.me/stumurray
