[FOSS-GPS] AGPS for newbies?
m.j.tandy at warwick.ac.uk
Mon Jan 19 09:16:47 EST 2009
2009/1/19 Lauri Hahne <lauri.hahne at gmail.com>:
> 2009/1/19 Timo Jyrinki <timo.jyrinki at gmail.com>:
>> In three kilobytes?
> That sounds credible. [...] I think your program requires coordinates
> only because the chip expects them with the agps data.
I agree with you that, with a single satellite's ephemeris data 900
bits long, one could send 32 satellites' ephemerides in 3.5 kilobytes.
However, the documentation for U-Blox's AssistNow Online service 
 explicitly says it only sends ephemeris data for visible
satellites, so that the data is "1 to 3 kilobytes".
You might ask why anyone would be worried about making such a small
amount of data even smaller. I can only assume it's because of the
usurious rates some telephone companies charge for data  .
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