NewsPeeps

Introduction On a stationary GPS without a differential correction signal, you should see a 20m average radius "random walk" pattern. On the same receiver with DGPS corrections and a good view of the sky, the error should be reduced to approximately 2m average radius. If you've always wanted to see how clean the GPS signal is once the government-induced noise signal is removed but didn't want to spend the money for a DGPS radio, here is your big chance!

I'd like to announce a fun DGPS hack. I've written a small Un*x server and client for redistributing DGPS correction signals over the Net. Basically the server grabs the serial byte stream from my DGPS radio and sends it off over a TCP connection. The client does the same thing but in reverse. The result is that you can receive the local DGPS corrections from absolutely anywhere by using the Internet as the world's largest extension cord. You'll still need to be within 1000 miles or so of San Francisco, California, USA for best results. However, chances are better than not that the GPS error will still be reduced if you are within a 3000-mile radius. Several respondents from 2000 miles away have noted that the remote differential signals have diminished the selective availability (SA) induced position and velocity errors by approximately a factor of three. Here are some plots illustrating the reduction of SA-related wander at a site some 3,500 km away. The red traces are with dgps-ip, the green without. [1] [2] Thanks to Tom Dunigan for contributing this data.