On Thu, 23 Sep 2004 18:25:33 UTC, "Gavin Hamilton"
wrote:

: It's been somewhat better than that for a while, since the "random error"
: was removed. IME the error is probably nearer 2 metres. Though the powers
: that be can reintroduce the random factor, or turn it off entirely, should
: they feel the need.

You have to be careful not to confuse the random precison errors with
the unrandom accuray ones. Civilian GPS is designed to be precise to
about +/- 10m, whereas military GPS, which uses different signals, is
precise to +/- 1m. Those errors are random - there is nothing you can
do about them. Selective availability was a deliberate degradation of
accuracy, done by effectively instructing satellites to tell porkies
in their signals, and thereby displace all GPS positions in a
particular area by an ordained amount. That's what doesn't happen
(much) any more, but the precision errors remain.

Ian
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