My Galaxy ACE SD card fills up with .txt files in the GPS folder when the GPS is on. I often run out of space. This doesn't happen with my other Android phones.
How can I diagnose and fix this?
It's most probably a buggy 3rd party app (preinstalled by Samsung or by you).
To find the offender I'd install Permissions and narrow the problem down to apps with precise GPS location permissions.
If you're rooted you could also run 'lsof | grep sdcard' to see which processes have these gps/txt files open and subsequently delete the offending app, here's a sample output: