How I use my GPS

I take my GPS everywhere I go with my camera and just leave it on. Using the free tools available at I download the logs from my GPS when I empty my memory cards. I often don’t have time to stamp the photos themselves, but always keep the GPS track logs with the photos for the future. To me it is more important to have the information available than to use it immediately. As long as it is recorded I can worry about how to use it later.

NOTE: 2006-11-24 – There have been some problems with the download page. The tools can be downloaded directly from Microsoft Reasearch. I have written more details about that here.

Some General Tips

  • Keep the camera time in sync with the GPS time. This is critical for automatic synchronization. It doesn’t have to be in the same time zone (more on that later) but the minute, and preferably second, should be the same.
  • Be aware that the WWMX Location Stamper is a bit dumb about time zones. More on that below

Getting the Track Log out of the GPS
I have the Garmin ETrex Legend GPS which is well supported by the WWMX GPS Track Downloader tool. It saves the track logs in the GPX file format. This is an XML based data format that is easy to read and is supported by many GPS tools.

Running WWMX GPS Track Downloader

  • Connect the GPS to the serial port and turn it on
  • Run the WWMX TrackDownload program
  • Select the “TrackLog Only” from the drop down list. The waypoints and routes are not needed for geotagging.
  • Select “Download From Device” in the Action menu.
  • When the download is complete choose a location to save it. I put it in the same directory as the photos I just copied from my memory card.

Tagging the Photos with Data from the GPS Track Log
I use the WWMX Location Stamper to stamp the photos. There are instructions given on their site and available with the tool, but here is a simple intro.

  • Start the WWMX Location Stamper
  • Select “Photos->Add Photos…” to load the photos you wish to stamp
  • Select “Tracks->Add Tracks…” to load the GPX file that you extracted from the GPS
  • When you load the GPX file the map in the tool should zoom in to the track points in that file. Be aware that if you have waypoints and trackpoints from around the world it will stay zoomed out. You should try and limit the content of the GPX file as much as possible (by not downloading waypoints with the track log)
  • Select the photos you want to tag.
  • Click “Apply Tracks”. I usually keep the default settings and select “Stamp the Photos”.
  • The photos should now be grouped into those that were stamped and the “Tricky Cases”.

At this point I check the non-Tricky Case photos and make sure that they are mapped correctly. If there is a problem with the time zones this is where it will appear.

Go through the Tricky Cases and check if they are correct. The reason why some of the photos are considered “Tricky Cases” is because the GPS was not on or not getting a good signal when that photo was taken. This can happen if you take photos inside when the GPS wasn’t working. You can toggle them between the following options by right clicking on each photo

  • “Last Known Location” – This is the last track point recorded before the photo was taken. This is usually selected by default if there is a long gap in the track points when the photo was taken (hours) and the photo time is close to the begining of that gap. This is common if you take a photo just after turning of the GPS for a day.
  • “Next Known Location” – This is the next track point recorded before the photo was taken. This, like the “Last Known Location”, is selected if there is a long gap in the track points and this was close to the end. This is commonly selected if you take the photo just after turning off the GPS.
  • “Calculated Location” – This is a calculated location between the last track point before the photo time and the next track point. It is calculated from the time the photo was taken. So if the photo was taken at a time one quarter between the last track point and the next then it will be one quarter away along the line between those two points. This is most often selected when the GPS was on during the signal gap and the gap was short.

If none of those choices is the correct location you can just drag and drop the photo at the location where you believe it was taken. This is helpful if you forgot to turn on the GPS or don’t have a GPS, but less automated.

Problems with WWMX Location Stamper
The Garmin GPS records the track logs in GMT. If you change the time in the camera to match the local time when you are on vacation or otherwise in a different time zone from your PC, then you should be aware of the issues that will occur when you try to stamp the photos.

When you are running the WWMX Location Stamper it has only the photos (stamped with local time) and the GPX file (stamped in GMT) and the current PC clock to work with. It assumes that the camera and PC are in the same time zone (which is true most of the time) and works backwards from that. If your camera was set to a different time zone, let’s say one hour ahead, when you took the photos, then the Location Stamper will incorrectly assume that the photos were taken in the PC time zone and all the photo locations will be off by an hour. To get around this issue there are a few options.

  1. Always keep your camera in your computer time zone. This should keep the times in sync, though I haven’t tried this
  2. Using the WWMX Location Stamper you can change the time stamps of the photos to adjust them back one hour (or from whatever time zone you were in).
  3. Set your PC clock time zone to the time zone you were in when you took the photos. This is my prefered option since it doesn’t require me changing either the GPX data or the Photo and the photos will remain stamped with the correct time. You must change the clock before you run the WWMX Location Stamper. Don’t forget to change it back when you are done.

Why I do not yet tag every photo out of the camera
My biggest concerns with tagging the photos immediately is losing data. I always keep a copy of the original unedited photos as they come out of the camera. With GPS data I hoped that I could simply geotag the originals and add some data without losing anything. Wrong. I discovered early on that the tools I was using (from to geotag the photos modified other meta data in the photo. I still do not trust any editing of the original photo files. This means that if I tag all my photos immediately that I will always have two copies, and that is a big waste of space.

I purchased a Canon Rebel XT DSLR camera shortly after I bought the GPS. It can take photos in RAW format. While the RAW files that it produces can also contain GPS data in the EXIF header (I have tested this using ExifTool), none of the available tools can geotag RAW files and none of the tools for processing RAW files into JPEGs will pass the GPS data along.

As usual I am a bit ahead of the technology curve and am waiting for the rest of the world to catch up. In short, I’m not incredibly satisfied with the tools that are currently available but I have the GPS track logs for most of my photos. Once there is a system that meets my requirements I will be able to show off my photos in a whole new way.