Record your geolocation!
The recordings can be shared as KML files via mail or sent to the ShutterSnitch photography app, that in turn can geotag all JPEG photos that matches the capture time.
Recording time can be set to half an hour, 1, 2, 5, 10, or 24 hours through the Settings app. But keep an eye on your battery level - it could run out before the limit is up.
Continued use of GPS running in the background can dramatically decrease battery life.