Aviation airport geolocation  - Page 1
Forum section: electronics / general

author: soldar
author_rank: Super Contributor
timestamp: April 20, 2019, 02:19:29 pm
content: Inanother threadsomeone posted a photo of a sign at an airport gate giving the geographical coordinates. I looked it up on the map and found some discrepancy and so I posted asking but got no reply or interest in that thread. I am still curious as to why the geographical longitude marked at airports do not match the WGS84 coordinates. Anyone?Quote from: soldar on March 26, 2019, 09:10:24 am

author: CatalinaWOW
author_rank: Super Contributor
timestamp: April 20, 2019, 04:57:10 pm
content: I know that there is much misdirection about "important" sites for a variety of reasons. Maybe someone considers an airport "important". In any case I am not sure the strategy is well thought out. A sophisticated entity trying to reach one of these "important" sites would not be inconvenienced greatly. Perhaps the decision makers were/are living in the past where simple subterfuges might be enough to hide something.

author: awallin
author_rank: Frequent Contributor
timestamp: April 20, 2019, 06:28:04 pm
content: Quote from: soldar on April 20, 2019, 02:19:29 pmcan't find much wrong with the one in Spain, google places a pin right next to "05"https://goo.gl/maps/sJFQTKXQZFw42or38

author: awallin
author_rank: Frequent Contributor
timestamp: April 20, 2019, 06:47:20 pm
content: googling landed me a picture of stand 16 - which seems to have roughly correct coordinates according to googlehttps://goo.gl/maps/5QnkNBdgDpxT25mx7

author: soldar
author_rank: Super Contributor
timestamp: April 20, 2019, 06:51:41 pm
content: Quote from: awallin on April 20, 2019, 06:28:04 pmYou are right. I must have made a mistake the first time around. I believe to main example is still wrong though.

author: soldar
author_rank: Super Contributor
timestamp: April 20, 2019, 06:52:39 pm
content: Quote from: CatalinaWOW on April 20, 2019, 04:57:10 pmNo, those are signs located at airport boarding gates so that pilots can zero their navigation systems. They must be good for whatever purpose they are supposed to be.An interesting case is China where official maps are distorted and the coordinates differ from WGS84. Using a GPS receiver in China is illegal (although the truth is nobody cares) and cameras and other devices sold in China must disable the GPS receiver when they detect they are inside China. IMHO it is crazy because, come on, America probably has better maps of China than China does. I really don't see what good it can do to them.https://en.wikipedia.org/wiki/Restrictions_on_geographic_data_in_China

author: donotdespisethesnake
author_rank: Super Contributor
timestamp: April 20, 2019, 08:27:09 pm
content: Quote from: soldar on April 20, 2019, 02:19:29 pmI would question the provenance of the photo. Clearly the longitude is wrong, but according to my investigation Tan Son Nhat International Airportdoes not have a Gate 10. The airport was remodelled in 2007, so maybe there used to be, although that still would not explain the wrong coordinate.Before concluding all airport gate location signs are wrong, I would look for some known good data.Update: gates 10-14 are described as "bus gates", i.e. passengers are taken by bus to plane on the apron. I'm not sure those are fixed locations, so I'm still not convinced this is a genuine sign.

author: soldar
author_rank: Super Contributor
timestamp: April 20, 2019, 11:06:32 pm
content: As the second photo turned out to be correct it may be this is just a bad photo somehow but I am still curious. I can't see why anyone would alter a photo like that.I did find the photo online when I searched last time but cannot find it now. Maybe Shutterstock or similar service.The difference in longitude is about 0.75º = 45' It does not seem like it could be a simple transcription error because several numbers would need to change.Maybe it is a single case and not a widespread thing as I first thought.

author: jc101
author_rank: Frequent Contributor
timestamp: April 21, 2019, 10:59:00 am
content: Well I posted that original pic which I just grabbed from Google Images as an example, no idea where it came from, it was just to show an example of what happens in aviation.Here is an example of charts, for Heathrow in this instance, where the stands and main areas are all referenced with GNSS coordinates.

author: soldar
author_rank: Super Contributor
timestamp: April 21, 2019, 03:24:01 pm
content: Quote from: jc101 on April 21, 2019, 10:59:00 amWhen you first posted it I searched and I found it somewhere and checked. Then I found another one and checked and I found it to also be mistaken and that is what sparked my curiosity.Now I find out I was mistaken with respect to the second one which turns out to be correct.So the scope of the question is greatly reduced from "why are all signs (I have found) wrong" to "why is one sign (which we can't even find now) wrong".