Re: 8 channel agps vs 12 channel non-waas

On Sun, 27 Jan 2008 09:29:53 -0800 (PST), Eric <egrumling@xxxxxxxxx>
wrote:

I recently bought a Nokia N800 with the Navicore navigation kit. My
plan was to use it with the GPS built into my phone via bluetooth. The
Navicore kit includes a 12 Channel BT GPS (Nokia LD-3W). My phone uses
A-GPS with an 8 channel receiver.

Not that it really matters much, but I got thinking about which GPS
would work better. My first thought is that the 12 Channel one would
be better, but A-GPS seems to be about the same, and locks on much
faster as well (as long as a tower is near). Does A-GPS do anything to
augment finding a solution, like WAAS or DGPS?

Has anyone done a comparison of of this sort? If not, in the interest
of wasting time, I'd be willing to compare the two, if someone can
steer me to a good testing method.
Once you get past 5 channels, the law of diminishing returs comes into
place with extreme speed most of the time. You need 4 sats for a 3D
fix. No more, and no less.

A fifth channel is useful for continuous almanac update, and to switch
two if you suddenly lose one of the active four. Most GPS units will
pick the 4 birds they can see that provide the best Dilution of
Precision (most accurate solution). So absent WAAS or Differential
operation, you are going to have a very hard time seeing a difference
between an 8 channel, a 12 channel or even a 20 channel unit. At the
end of the day, they all end up using the same 4 birds to calculate
the same position.
.

Relevant Pages

  • questionable "Number of Tracking Channel" of a receiver
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    (sci.geo.satellite-nav)
  • Re: AIS Position Error?
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    (rec.boats.electronics)
  • Re: New GPS comming soon/rumors?
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    (sci.geo.satellite-nav)
  • Re: relying on GPS leads to accidents
    ... marking the channel just east of the point where he crashed into the jetty. ... It doesn't sound like the GPS was even slightly at fault in this case. ...
    (rec.boats.cruising)
  • Re: 8 channel agps vs 12 channel non-waas
    ... plan was to use it with the GPS built into my phone via bluetooth. ... Navicore kit includes a 12 Channel BT GPS. ... A-GPS with an 8 channel receiver. ... they all end up using the same 4 birds to calculate ...
    (sci.geo.satellite-nav)