GPS position is inaccurate

[gd5362]

I have a Challenger Lite and the GPS position relative to the airport is not accurate. GPS navigation works well to get me to the general area of the airport and the GLS approach will show the runway off to the side.
I have tried moving the antenna to several locations and will receive 8-13 satellites reliably depending on location.
Any ideas?

Glenn Davis

[Sputnik]

I doubt it’s your GPS position; far more likely it’s your runway end coordinates, which are only as good as the database they came from, as modified by any loss of precision due to anyone chopping off significant digits along the way.

Have you tried another runway? Another airport? What airport are we talking about? Is it in the USA?

Probably you’re going to have to edit your runway end coordinates. Worse, you might have to do so with every database update....

[gd5362]

Thanks for the reply Sputnik,
Very small airports in the USA and they are all about the same distance off. Your reply was what I was afraid of.

Thanks
Glenn Davis

[hpmicrowave]

If you send me the coordinates in your data base for your airport, and the airport identifier i will check on google earth and compare. Coordinates pulled from Google earth i have found to be less than 3 meters. You can check yourself also. I check/verify Google Earth accuracy (coordinates) by looking up the FAA coordinates for IFR Runway approaches, FAA has them nailed to where the Runway centerline starts at the approach end of each IFR Runway approach. Then put those into google earth, they will match up with the same runway centerline point, and you can easily verify how accurate the coordinates are pulled from Google earth.

Cecil

[gd5362]

Thanks Cecil,
How do I access my coordinates in my data base ?

Glenn

[PaulSS]

Are you saying the representation of the co-ordinates is not aligned with your raster map? For instance you select a waypoint and it is off to one side on your raster map. If so, it sounds to me like the geo referencing of your raster map is a bit off.