S22 ultra (Exynos) GPS problems with bizarre GPS altitude

[Iain_F]

Hi,

I'm getting very variable GPS accuracy in my photos. I use an app (Neofinder) that shows the GPS coordinates and altitude. The accuracy is variable, sometimes dead on but often out by up to 100 metres. 

In addition to the location I also get the GPS altitude and this is out by approximately 40 metres even when the GPS location is accurate. Is this part of the problem. I know the altitude is wrong because the photo is taken on a jetty.

Could this be part of the GPS problem or is it unrelated?

Any thoughts?

Cheers

Iain

[MickJG]

GPS altitude will always be hit and miss, or more to the point, quite inaccurate. It's very difficult for satellite location to be accurate for height above sea level when they are so far away effectively above your head, and not at your sides. Barometric altitude is the way to go. And yes the S22 ultra does measure that, not sure if it stores that info in a photograph file.

[Iain_F]

OK then, but I'm puzzled. As I understand it, as the phone is getting signals from a number of satellites shouldn't the GPS signal give a 3D position with accuracy the same for height as well as horizontal location?

[MickJG]

A quick Google will tell you gps elevation accuracy is good for + - 400ft. So around your 100m
Military gps data is more accurate than civilian from what I've been told. But either way, calibrated barometric altitude is what you need, and is what aviation uses.

[Iain_F]

Hmm, OK. After a bit of searching, I got a number of hits suggesting that you are correct e.g.

The general rule of the thumb is that vertical error is three times the horizontal error. If a decent signal reception is available, a modern GPS receiver should be able to give elevation data accurate to a range of 10 to 20 meters (35 to 70 feet) post correction.

However, if this is the case, the S22 is still out of this range by a factor of 2