The project I’m preparing to work on (tentatively dubbed PathTagger) makes extensive use of the Global Positioning System to calculate a user’s latitude and longitude.
In order to experiment, I picked up the TrackStick 2, a portable GPS data logger, which promises 2.5 meter horizontal accuracy. You can pick it up on Amazon for about $150. (Unfortunately, the iPhone’s GPS can’t run as a background process which makes it useless as a data logger because you would have it open the entire day and even if you tried that, it’d eat up your battery in no time… damn technology.)
I’ve been playing with the TrackStick for two days and I’ve had mixed results.
On one hand, it’s small enough to fit in your pocket and, for the most part, it does what its supposed to do.
However, there are a few ares that could be improved.
The signal strength has been sporadic, to put it mildly. It does not work in any of the buildings I’ve been in and even when I’m outdoors, the signal seems to constantly fades in and out.
For example, I went on a short drive, making two stops along the way, one at Starbucks and one to pick up some sushi. It correctly recorded my commute to Starbucks, but then missed the short drive to the sushi place and the time I spent in that building. Once I left, it picked up my signal again and correctly recorded it until I got home. Subtracting the time I was still (it is designed to group stationary periods), I get that it worked a little less than 45% the time.
Then there’s the path itself. Here’s a portion of a the trip plotted on Google Earth:
I was traveling on the right (top) side of the road in the far left lane. The two points used to plot this line are approximately 120 feet and 35 feet from that line, quite a bit more than then 2.5 meters (8.2 feet) promised. Small sample size? Yes, but it’s not much better anywhere else on the trip. The farthest distance from my actual route was about 300 feet, or about 36 times their 2.5 meters.
That being said, I still think it’s pretty cool and am happy I bought it, even if it does think I’m driving in the trees.
More to follow as I get additional data.