Selective Availability - the system that gave civilians a degraded GPS
compared to the military - was turned off in 2000. Wikipedia (of course) has
a pretty good article on GPS describing the various sources of error and
what can be done to improve accuracy.
But as you say 10m is pretty good for most birding locations - unless you
are trying to pinpoint a specific tree in a dense forest, in which case GPS
will probably not be getting signals anyway so will be useless!
2009/12/28 Peter Shute <>
> Regarding GPS accuracy, my phone generally claims the coordinates are
> within 10m, sometimes much lower, occasionally higher. I would imagine
> that's easily good enough for finding most birding locations again, what
> kind of accuracy are you talking about?
>
> I'm under the impression satellite signals are deliberately encoded to
> prevent civilians getting too much better accuracy than that, for military
> reasons, including making it hard to pinpoint the location of the actual
> satellites in order to shoot them down. To get better accuracy (precision
> might be a better word), I think a long succession of coordinates must be
> averaged. This may be what the more expensive gear does.
>
> Not so very long ago, GPS wasn't even an option. The alternative for those
> without access to expensive electronic distance measuring equipment was a
> tape measure or triangulation. In my opinion, the decision by the USA to
> release even this level of accuracy to civilians is absolutely wonderful,
> even if it does occasionally lead you back to the wrong side of the creek.
>
> Peter Shute
>
>
> --------------------------
> Sent using BlackBerry
>
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