(Please note that I am copying this message to the OpenStreetMap folk: http://openstreetmap.org as we will hopefully find more GPS/mapping experts there. Please edit the list of recipients if you need to.)
On Thu, 27 Mar 2008 14:24:56 +0100 [EMAIL PROTECTED] wrote: > Hi all! > > After hours of searching the web for information about the new Antaris GPS > chip I am still not sure if it will be possible to use the raw data output of > the ATR0635 (message type RXM-RAW) on the Neo FreeRunner. This message > should, according to the protocol specification [1], contain information > about the per-satellite errors necessary to build something like > a "cooperative differential GPS" [2]. Such an application could - in theory - > greatly improve the accuracy of the Neo-GPS and therefore open it up to a > whole new range of use-cases. [...] Thanks for bringing this up, as this is is a topic that I am very much interested in. We are just starting to explore this area, but the AGPS capabilities of the Neo 1973 was one reason that we went ahead and bought this. However, I do not know what AGPS support means in real terms. My naive understanding of this is that a cooperative differential GPS needs no external support. One just sits at a base station, and averages GPS readings until one knows the position of the base station to an arbitrary level of accuracy. After that, the reception of realtime GPS signals at the base station provides information about random errors, which I understand are largely due to atmospheric fluctuations. Corrections for these are derived from the difference between the well-known actual position of the base station, and the received realtime position. These can be broadcast through various means, e.g., an Internet DGPS server, and should be good for a few hundred km around the base station. The cooperative aspect of this comes in because of the benefits of multiple base stations. I would love to be corrected on the above by someone who knows better, as this is little more than a surmise on how DGPS should work. Regards, Gora _______________________________________________ talk mailing list [email protected] http://lists.openstreetmap.org/cgi-bin/mailman/listinfo/talk
