Improved GPS Activity Tracking

Activity Traces

I’ve been using my iPhone to GPS track various activities for a number of years. I love how easy it is to integrate various data sources via Bluetooth. Having heart rate, bike speed, and pedaling cadence tracked along with GPS is fantastic for post-activity review. I was never particularly happy with the GPS performance of the older iPhones. When I directly compared the iPhone 4S to a purpose-built GPS (the Locosys GT-31; which I bought to use windsurfing and sailing), the results were as expected: the GPS tracks from the GT-31 were much more accurate.

I wanted the accurate GPS along with all the extra data collected by the iPhone, so I carried both. To combine the two data sources I put together a simple script in R that replaces the GPS track in the iPhone data with the more accurate data from the GT-31. The script is available on GitHub.