John F. Eldredge <[email protected]> wrote:
>... both car and cell-phone GPS is that it seems to be more accurate
>when I am moving than when I am standing still.
Many GPS units use something called "pinning" so that when you are stopped,
your GPS coordinates will still show as stopped. Without pinning, it is
perfectly normal to see the coordinates reported by a stationary GPS change
slightly ("jitter").
One typical algorithm used for pinning is to look at both the reported speed
and position. If the speed reported is high enough, the newly calculated
position is reported. If the speed is too low (typically < ~5kph), newly
calculated positions are not reported until they show a nominal movement
(several meters).
Pinning may work well for things that move quickly, but it can cause some
interesting problems with it when doing activities like hiking, walking, and
Geocaching.
- John
--
John Werner
http://www.snowtire.info
http://www.frontiernet.net/~werner/
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