Re: GPS unable to lock while moving

On Tue, 26 Jul 2005 13:51:23 GMT, "Pieter Litchfield"
<pvcl@*nospam*plitch.com> wrote:

>I would disagree - I have had otherwise excellent retail GPS receivers be
>unable to get enough information to get a fix on startup in a moving
>vehicle. When the vehicle is stopped (without changing the GPs position
>inside the car) it will rapidly get a fix. I have seen the same happen on a
>bicycle!

Pieter,

I can confirm that. My guess has been that the receiver has to
make assumptions about the relative speed of each satellite to
receive any data, and its first assumption is always that the
receiver is not moving.

The faster it moves, the harder it is to get a lock. In an
airliner it can take 5 minutes.

>Once the almanac is
>downloaded and a fix is obtained, then movement has little impact. I'd
>suggest getting a current poition fix before getting under way. In my very
>subjective experience the same seems to also apply to WAAS "lock" as well -
>best to establish a WAAS connection at standstill.

Agreed as well.

Hans-Georg

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.

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