Digital Shiv

Open Source Real Time Kinematic GPS with accuracy to the centimeter

By runagate

Make Magazine brought this Open Source real time kinematic GPS receiver to my attention and, having just started development on a device with a GPS receiver with plans for an Augmented Reality musical controller interface, the claim that Real Time Kinematic GPS can give accuracy of centimeters instead of traditional civilian GPS of about 16 feet or so, I was intrigued by the possibilities:

“Want to fly your plane or drive your car using GPS signals, but finding that your receiver just isn’t accurate enough to make things work? Well, MAKE subscriber Bruce Mueller writes in to point us at an impressive solution: an open-source real time kinematic GPS receiver. Researchers Tomoji Takasu and Akio Yasuda of Tokyo University developed the RTKLIB library to perform the RTK-GPS calculations, and then ported the whole thing to run on a low-cost beagle board and commodity GPS receiver. Want to try it out? Full source code, circuit layouts and instructions are provided on their site.

So, how does it work? A GPS receiver normally works by measuring the delay between an internally generated signal and one received by a satellite. This specially crafted signal makes it possible for the GPS receiver to find and latch onto the satellites signal, however it’s wavelength limits the accuracy of the receiver. The real time kinematic system gets around this limitation by measuring the phase delay in the carrier signal. Because this signal has a much sorter wavelength, it is possible to make a system that is accurate to the centimeter”

Whether a mobile device’s GPS can be hacked with the Open Source software to usably enable small-scale Augmented Reality position sensing remains to be seen.