NMEA gpsRecorder is a program that allows you to record, at predetermined time intervals, your GPS position and to save the data, in a NMEA-0183 compatible format (record types GGA and RMC), into a log file exportable using iTunes. Each Start/Stop, done using the "Record" switch, creates a new log file identified by an increasing number.
By recording the GPS coordinates you can later know exactly your position for each time interval, allowing, for example, in an extremely simple way, the geolocation of your photos or the tracking, on maps such as those of Google, of the path you made.
Before starting your trip, open the program and let 'NMEA gpsRecorder' active (also if your device is doing other thigs). Back to home, download the data with which you can geotag all pictures taken during the day.
Please note that the continued use of GPS running in the background can dramatically decrease battery life.