[FOSS-GPS] AGPS for newbies?

Michael Tandy 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 [1]
[2] 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 [3] [4].

[1] http://www.u-blox.com/services/assistnow_framework.html
[2] http://www.u-blox.com/products/Product_Summaries/AssistNow_Prod_Summary.pdf
[3] http://www.crunchgear.com/2008/07/01/atts-text-messages-cost-1310-per-megabyte/
[4] http://news.zdnet.co.uk/communications/0,1000000085,39235137,00.htm

More information about the FOSS-GPS mailing list