A work in progress, detailing how to use a 3rd party gps unit not intended for use in getotagging in geotagging (read it again, it makes sense), using only free tools.
1) convert whatever gps file format you have to a gpx file format. For me it’s a garmin.
gpsbabel -t -i garmin -f usb: -o gpx -F tracklog.gpx
2) use the gpx file to tag all the photos. I’m not sure about the timeadd thing. Has to do with time zone. I think it’s possible that I can get away without it. Anyways I’ll have to try. There’s also a clever gui (which I haven’t yet looked at) for gpscorrelate, which might add in figuring out what’s going on with timezones.
gpscorrelate –gps tracklog.gpx –timeadd -5 *.jpg
It’s worth reading what this character has to say about the topic.