Nokia N900

[Joshua Judson Rosen]

David Rysdam <david at rysdam.org> writes:
> On 05/12/2010 01:46 PM, Joshua Judson Rosen wrote:
> >
> > This is why I'm dubious of these `N810's GPS receiver is slow' claims--
> > because coupling them with `... so I never use it' is actually a
> > vicious cycle. 
>
> Are the claims peculiar to the N810?  If not, perhaps you are right.
> What other not-always-on-the-internet devices that support GPS as a
> non-main feature are there?
>
> I could do a test.  Get a fix, drop it, wait N hours and reacquire.
> Graph reacquisition time against N.  Except I'll never have the time for
> all those tests, so I'll just do one if you suggest a value for N.

Well, the way I interpreted your described use-pattern put N
somewhere in the thousands. ;)

My suggestion is to duplicate the ranges of N described in this here
page that I found:

     http://www.pocketgpsworld.com/ttffcomparisons.php

... noting that "between 8 to 12 hours" means that you
want to have had a successful fix *within the past 12 hours*; and that
you want to be sure that you actually wait for a `3-D fix', because
you can get a 2-D fix before you have enough data to get a 3-D fix,
and some elements such as GPS time can become available without having
attained fix.

Summary:

    Cold tests

         were performed when both Pocket PC and GPS receiver were
         powered off (if GPS receiver has a separate power source, the
         GPS receiver was unplugged) for a period of between 8 to 12
         hours requiring a cold start.

    Warm tests

          Warm tests were performed when both Pocket PC and GPS
          receiver were powered off (if GPS receiver has a separate
          power source, the GPS receiver was unplugged) for a period
          of 30 minutes
 
    Hot tests

          Hot tests were performed when both Pocket PC and GPS
          receiver were powered off (if GPS receiver has a separate
          power source, the GPS receiver was unplugged) for a period
          of 15 minutes


And, of course: be sure that you are outdoors with a clear sky,
and that you have a nice wide view of that sky.

It'd probably be worthwhile to take note of both the `2-D fix' time
and the `3-D fix' time, and the length of their delta.


> I will note, though, that when I first unpacked my actual GPS it
> acquired a signal in just a couple of minutes *from inside the house*
> whereas the N810 has rarely done it even standing in the yard for
> significant fractions of an hour.

Pshaw--I bet that's another trick: they probably preprogrammed it with
your shipping-/billing-address, just to make themselves look better ;)

-- 
"Don't be afraid to ask (λf.((λx.xx) (λr.f(rr))))."