Mark J Cox
mark@awe.com
   


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03 Mar 2008: Geotagging and route logging with Tom Tom

I'm out on holiday soon to Arizona, so we've been looking for ways to geocode the photos we'll be taking and get a record of our route. I use a Mio A701 phone which has built-in GPS, and this time we'll be using Tom Tom in the USA rather than Mapopolis. The problem with Tom Tom Navigator is that it doesn't keep a track log, and there doesn't seem to be any plugins to allow it to do so. So here is the solution I've been experimenting with over the weekend.

On the PocketPC:

  • Make sure the GPS Intermediate Driver is enabled, on the MIO there is a built-in "GPS Settings" utility where I have it set to COM4 and "Manage GPS automatically"
  • Use the GPS2Blue utility. Make sure it's set to GPS on COM4, 4800 baud, with logging only of GGA/GLL/RMC/VTG NMEA, and select 'Log processed raw data...'. You don't need to enable the "2blue" bit, we're just using it to write the tracklog.
  • Make sure your camera has a date and time that is close to the one being shown by GPS2Blue from the satellites
  • Start TomTom. Make sure it's also set to COM4, 4800 baud. This will work because the GPS Intermediate Driver is opened by GPS2Blue. You can't start TomTom first, but you can exit GPS2Blue and leave TomTom running.
  • After finishing you end up with a NMEA track log with an hour of logging taking up about 1.6Mb. Transfer it to your Fedora machine.

On my Fedora machine:

  • Use gpsbabel to convert the NMEA track log and clean it up a bit. I used: 
    gpsbabel -i nmea -f GPS_2008-03-03_122630.log -x discard,hdop=10,sat=5 -o gpx -F out.gpx
  • Use gps2photo.pl to add the geocoding to your images. This script looks at the time and date the photo was taken and tries to match it up to an entry in the tracklog, so you may need to play with the timeoffset to deal with timezone differences. Although we have snow, being in the UK in the Winter has it's advantages as we're UTC+0, so I just used: 
    gpsPhoto.pl --geoinfo=osm --dir ./ --gpsfile out.gpx --timeoffset 0 \
    --city=auto --sublocation=auto --state auto --country auto --kml out.kml

The exif metadata inside each jpeg now contains the approximate co-ordinates of where you were when you took the photo along with a guess of the location (city, country, etc). You can load out.kml into GoogleEarth to see the tracklog and photos on a map. If you've allowed Flickr to read the location data from exif then uploading a geotagged photo will automatically place it on a map. (Make sure you consider the consequences before enabling that option or you may end up unintentionally leaking information like the location of your friends houses or parties you've been to). Here's a quick pic taken in the snow today to test it out:

Test of photo Geocoding output from exiftool: 
GPS Position                    : 55 deg 46' 58.21" N, 4 deg 0' 5.50" W
City                            : Motherwell
Province-State                  : Scotland
Country-Primary Location Name   : United Kingdom

Created: 03 Mar 2008
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