On Fri, 4 Feb 2011 16:17:09 +0100 Stefan Keller <[email protected]> wrote: > Now given that mobile phones can be connected to low-cost GPS (e.g. > via bluetooth) it should be possible to implement at a "consumer DGPS" > which gets an accurracy of 2m or better.
Sorry for an email that includes SWAGgery, I haven't done this yet so there are a few "try this", but I'm interested in pursuing it further. Some of those low-cost consumer grade devices already integrate SBAS (Space-Based Augmentations Services) correction like WAAS, EGNOS and MSAS, which can put them close to 2m. These systems work by having a network of ground reference stations which broadcast error back up to the satellites, which then send it back down to your receiver. My EM-406A module, SiRF III chipset based device, which I've incorporated into an Arduino based GPS logger, does this. On the other hand, data from my Wintec G-Rays 2+ indicates that it probably does not. You can get free reference data from the NOAA CORS project. It looks like you could use GPSBabel to get data into NMEA 0183, and then use RTKlib to apply the CORS data back to those samples. However, a good portion of the additional error you're seeing with cheap GPS receivers with tiny little antennas is probably multi-path error, and DGPS won't help you with that. It'd be worth playing with, though. I may have to see if I can apply CORS data to the output from this morning's bike ride... Dan _______________________________________________ Geowanking mailing list [email protected] http://geowanking.org/mailman/listinfo/geowanking_geowanking.org
