I love animating bikesharing systems, but without GPS data it looks like people travel in straight lines, from bike-out to bike-in. So to get a better idea of how cyclists really travel across the city, I wanted to investigate mapping multiple GPS tracks.
The first step is finding data. Strava has a huge repository of bike data, but you can’t access a trips’s GPS data unless you are connected to that person, or if they otherwise grant you access. And even then when you download the GPS data the GPX file doesn’t include timestamps. You can get an idea of the potential of Strava’s data from this “Beautiful Weekend” video made by BikeArlington using VeloViewer.
I decided to try to collect my own GPS data by asking a local monthly bike ride, the DC Bike Party, to record their outing and send me the data. Their April ride attracted 650 riders, but I got only 5 responses, and one of those I had to reject for not having timestamps. But four cyclists is good enough for an experiment to learn more about the process.
The next step was data munging. One participant sent me two separate GPX files, for before and after the break at the bar. It was easy enough to merge them by taking the trkpt tags from one file’s trkseg section and adding them to the other file’s trkseg section. Another participant’s GPX file wasn’t syncing up with the others. To correct it, I just manually edited the timestamps using a global search & replace for the hour field. » Continue Reading…