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GPS Gadgetry
07/18/07 17:57 , Categories: random ramble 
As I said a few days ago, I've been out geocaching quite a bit in my spare time this summer. I've also been playing with my old (and wearing out) Garmin eTrex Legend hand held GPS. It was fancy in its day, but now it lacks some features such as turn-by-turn directions, a color display, a microsd memory card slot, and a magnetic compass that the new models have. To keep the buttons working on my trusty eTrex, I occasionally have to bang the unit against a rock, tree, or whatever is handy. And the screen sometimes flips out with alternate lines in the LCD display blanking out. Again, a light tap seems to fix the problem. I think to myself, it might be time to go shopping.
Aside from drooling over the new GPS receiver models from Garmin, I have been playing around with free mapping software like Google Earth and Google Maps. And I've found quite a few new ways to make use of my Garmin eTrex's computer interface cable to transfer information back and forth.
First, I noticed that geocaching.com allows you to download bookmark lists of cache locations into a gpx file. And using the program EasyGPS I can download these cache locations directly into my eTrex via the serial cable, saving typing. I thought that was pretty cool.
Next, I realized that EasyGPS had downloaded my "tracks" and "waypoints" from the eTrex and let me save them as a GPX file on my hard disk. This makes me very happy because I know that Google Earth can open a GPX file. Every place I marked with my GPS over the years was now posted on Google Earth maps. In addition, everywhere I walked or drove recently while the GPS was powered on was marked with a white trail on the map in Google Earth, like the picture above from last weekend's "tour de cache II." These are the "tracks" that the GPS automatically records whenever it is turned on.
That was all fun, but the most interesting trick I found had to deal with automatically putting pictures on a map. I went out and hunted for caches last weekend. I left my GPS running, plugged into the electrical outlet in my pickup, as I drove across the countryside and hiked through the brush. I occasionally stopped to take pictures. I hunted for the caches, and took more pictures. I had no idea that it would be so easy to combine my digital images with GPS data.
Today I saw an article about some software called PhotoMapper that would take the timestamp recorded by my digital camera in the image, combine that with the track log recorded by my GPS, and figure out the latitude and longitude at which the picture was taken. It then encoded that latitude and longitude into the digital image file in a standardized way.
So why is that interesting? Google's Picasa and some other similar sites can read that information and will stick the photos on a map. If you click on the image above or right here you can see how Picasa Web placed my photos on the map, almost exactly where I took them. Just click the "view map" button. Click on a thumbnail and then click "play" in the popup bubble for a slideshow on the map. The clock in my camera must be a few minutes off of the GPS time, but it's close because the locations are not far off on the map. In most cases just a few hundred feet. Next time I'll check the time on my camera.
I'm amazed how easy this was and that it's all done with free software. Even a low-end Garmin hand held GPS and digital camera can do this stuff.
For more details, I recommend checking out these sites:
