Date: Thu, 4 May 2000 01:01:25 -0700 (PDT) From: Matthew Dillon <dillon@apollo.backplane.com> To: Poul-Henning Kamp <phk@critter.freebsd.dk> Cc: Warner Losh <imp@village.org>, hackers@FreeBSD.ORG Subject: Re: GPS heads up Message-ID: <200005040801.BAA67715@apollo.backplane.com> References: <2288.957418565@critter.freebsd.dk>
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:SA *can* be averaged out, it has an average value of zero. But it
:takes several days or even weeks to get into the centimeter range,
:depending on the satelite coverage where you are.
:
:--
:Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
:phk@FreeBSD.ORG | TCP/IP since RFC 956
Months or years to get into the centimeter range.
Days to get in the 50 ft range, weeks to get into the 14 ft range.
That's based on measurements. And SA does *NOT* have an average value
of 0 even if you take a month's worth of data. Try to depend on the
average and you will be screwed. What you do is use the worse case
error (over a couple of days) to create an area, then take the middle
of the area. That will give you better results then an average (the
points within the volume will not be spread evenly so taking an
average will result in an offset).
-Matt
Matthew Dillon
<dillon@backplane.com>
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