Archive | November 16, 2010

Measuring Travel Times with GPSTrack: Monday, Nov 15th

In gearing up for a research project on travel times to health facilities in developing countries, I used a GPS app for my iPhone to track my travel route yesterday. GPSTrack is a free app which tracks one’s lat/long positions and elevation at intermittent points throughout a specified time window (you can pause it, it’s a battery hog). One is then able to export the points as a data file and can then import it into a GIS program such as ArcGIS to view it, as I have done to the left. A close of up my travels through Central campus on my lunch break gives you an idea of the accuracy of the readings. It’s pretty good; I can even track my movements within buildings:

The app not only allows one to produce pretty pictures, but, with a little computational pushing can allow one to calculate speed travelled between points. Below, I have two graphs, one is on an absolute time scale, the other is just for the series of measurement points, ignoring the time that passes between points:

It’s pretty easy to spot the difference between travel by foot and by bus, and to notice that I do a lot of sitting on my butt throughout the day. Unfortunately, travel distances while in front of a computer are 0. You can even spot stop lights and pausing in front of doors, desks, etc.

A cool feature is being able to track changes in elevation throughout the day, as I show below. To get from North Campus (where I live) and Central, one must travel through a bowl along where a river flows, hence the dips.

All in all? A cool free app. Unfortunately, the data export requires a little coaxing to get it to do what you want to do, and you have to filter out odd points when the cel phone is trying to figure out where you are. However, for the price, it’s worth it. In the future, we hope to attach GPS readers to mothers on their way home from health facilities, in order to accurately track the amount of time and the means of getting there and back.

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