[Geowanking] Low-cost GPS receivers and software for DGPS?

Dan Lyke danlyke at flutterby.com
Fri Feb 4 07:52:13 PST 2011


On Fri, 4 Feb 2011 16:17:09 +0100
Stefan Keller <sfkeller at gmail.com> 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





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