Thursday, April 22 2010


Geotagging your photos is both fun and useful, and not just for big trips like Japan, where I often had no idea where a bus was taking us. I think it’s nice that they’re starting to integrate it directly into cameras, but there’s a problem with that idea: satellite acquisition takes time, especially if it’s been a while since the device was last turned on.

The problem with putting the GPS into the camera is that people turn their cameras off. So, either the GPS stays active and drains the battery, or your first half-dozen pictures at each stop may look like this:


Standalone GPS trackers have their own problems, of course. Some have poor battery life, some don’t show up as simple USB mass-storage devices for transferring logs, some have poor chipsets, and most do not have a screen that shows the current time. That last bit is perhaps the most important, because your camera and your tracker have to match up by timestamp. Most software supports adjusting the time to improve the match, but for best results, you want to set the camera to GPS time, every day.

[Disclaimer: this particular picture doesn’t actually demonstrate the cold-start location problem. In fact, the cluster of accurately-tagged images in the upper right were taken first, and the half-dozen trailing off to the lower left were the result of the tracker losing signal when we got into the car, and not getting another satellite fix until we were several blocks away. Because the clocks weren’t in sync, the software assumed the pictures were taken while the car was moving, and interpolated their location between the two points. Easy to fix, but still amusing.]