Re: birding-aus GPS

Subject: Re: birding-aus GPS
From: Paul Taylor <>
Date: Fri, 20 Aug 1999 13:36:36 +1000
Tony Russell wrote:
> Morning all.
> I have a hand held Magellan Pioneer GPS which I now wish I had not
> bought, it's a real pain and an embarrassment.
> [snip details of slow lock on etc.]

There is a lots of information on this and many other GPS topics
on Joe Mehaffey and Jack Yeazel's GPS Information Website,

"Cold start" and "warm start" do not refer to temperature, instead
the refer to how much data the GPS has to work with (time, location,
and satellite almanac and ephemeris data.)  The more data it has
to work with, the faster it will lock-on.  If you are moving or
don't have a clear view of the sky, lock-on times are increased

If you are planning on taking frequent position fixes through the
day, you want to maximize the chance of getting a "warm start" fix
than a "cold start"  If you can't leave your GPS switched on all day,
you should try and leave it switched on for as long as you can as
often as you can.  Allowing ten minutes to get a good position fix
and sufficient time to update the satellite data will greatly improve
subsequent lock-on times during the day.

The satellite ephemeris data needed to obtain a position fix is sent
by each satellite individually, and is valid for only a few hours.
The satellite almanac data is used to determine which satellites are
"visible" without having to search for them; this is valid for several
months, so you should turn your GPS on once a month for around ten
minutes to keep the almanac up to date.  Similarly, the very accurate
time signal is carried by all satellites.

   Paul Taylor                           Veni, vidi, tici -
                    I came, I saw, I ticked.
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