The Perfect Sunrise

by NULLZ

submit your photo


Hall of Fame
View past winners from this year

Please participate in Meta
and help us grow.

Take the 2-minute tour ×
Photography Stack Exchange is a question and answer site for professional, enthusiast and amateur photographers. It's 100% free, no registration required.

I tried to geotag my photos from my DSLR using GeoSetter software. Although I corrected the time shift (I had 16 minutes difference between camera and GPS time) I am still unable to geotag my photos correctly.

For example there seems to be still more than 30 minutes or more than 5 km difference - I checked it using a photo of some lake for comparison with a google hybrid map.

All the photos were taken from a helicopter during some monitoring and the average speed was 120-150 km/h.

Geosetter

Full resolution image is here. The displayed photo of the lake was taken approximately from the position marked by the white hand cursor, while Geosetter locates it far away - the yellow dot in lower right corner.

Any idea, where could be problem?

PS: I used my SE Xperia Pro phone with OruxMaps to record the gpx file. The initial and final photos from the airport are OK.

share|improve this question
2  
Personally, I think the problem might be in the phone GPS. I don't think its actually a GPS but some type of an a-gps system with some wi-fi/cell-site positioning triangulation. Even a tru low-end Garmin GPS would have problems with positioning accuracy at those speeds without an external antenna. Just a thought. What is the accuracy like when you are on the ground? –  Jakub Apr 24 '12 at 15:28
    
Jakub: a-gps was not used as I had no wifi connection on board and I have mobile data (GPRS/3G) disabled by default. About the "true GPS" devices - we use one measuring device which uses Pharos Traveler 535v PDA as display and to get GPS data and it works very well on board without external antenna - but it has GPS Sirf Star III chip inside. About the accuracy of the phone GPS - I checked it and it is about 5 m outdoors, while in my office it was 9-40 m with 9 satellites. –  Juhele Apr 25 '12 at 5:37
    
Yeah I don't know much about how 3G mobile devices interact with satellites. I am surprised its reporting satellites at all but if it does not have a GPS chip it's probably the 3G network passing along the information over the network. 9-40m is pretty bad even for a cheap GPS unit with 9 satellites locked in. I would still blame it o the 3G network and the triangulation. –  Jakub Apr 25 '12 at 13:47
    
It has a GPS chip. I am using GPS Status sw: play.google.com/store/apps/… so I do not know how reliable is the information. And about the 3G - I have prepaid card so I surely would notice use of mobile data as I would get a billing sms message after every data connection. My colleague promised to take his Holux GPS logger so I will try to geotag the photos using the gpx from it and will see... –  Juhele Apr 25 '12 at 14:07
add comment

1 Answer

I'm not used to GPS but let's use logic,

You say that your starting and ending points are correct. They are also the only ones where your altitude with respect to the ground was 0, so was your speed.

  • GPS gives a 3-dimention position (including the altitude) but on the map you have only a 2d position: at some point there is a projection from the 3d coordinate to the 2d one.

You may check how this conversion is done, since they seems to have some systematics in the way your position are off (looks like they lies on parallal lines north-east of your track)

  • Speed may certainly interfer with the position determination but as I say I do not know enough GPS to assert this point.
share|improve this answer
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.