GPS lat/long accuracy issues?

[raldo]

Hi,

I've tagged some of my images using Geosetter which uses exiftool under the hood AFAIK.

I've now noticed that some locations seem to be offset somehow to a slightly different position. Maybe 50 meters off (max) North and 10 meters off East.

Since many tags have ended up in the same location, I'm suspecting some kind of rounding error, either in the Geosetter GUI or in the lat/lon metadata.

If there is a roundoff errror in the jpg lat/lon fields, I'd thhink that one should see such effects in Picasa too.

Has anybody seen effects like these?

[Phil Harvey]

This is definitely something to ask the Geosetter author.  ExifTool just writes what you tell it.

How are you reading the GPS back again?  Try using "exiftool -n" to see if the tags really ended up in the same location.  Maybe the software you use to display the position does some rounding.

- Phil

[hrpan]

I've tagged some of my images using Geosetter... ...there is a roundoff errror in the jpg lat/lon fields...?

Hi,
I'm not familiar with Geosetter, but I assume it's a program that derives geographical locations based on the exif timestamp of image files and .gpx log file. If you have the original .gpx log files, you may want to compare the results you are getting from it with those generated by Vagabond; see:

http://vagabond.sealug.com/

Assuming precisely set (or "delta-defined") camera clock, and constant speed linear movement between GPS fixes in the log, Vagabond precision is very high; probably higher than the GPS device itself. I also believe it was very well tested, including locating of images taken from high-speed trains. Note that Vagabond is a suite of comand-line tools, and, intentionally, does not change the content of original camera files: it creates instead a separate text file of filenames and locations. (full description and documentation is provided on the web-site given above). 

hrpan