Do the units any of you guys use make use of the
"WAAS" (Wide Area Augmentation System) data
transmissions?

Some of the newer hand-held GPS receivers do, and
some made a year or so back can be re-flashed
to yield this function (a friend updated his awhile
back for this functionality) ...

WAAS can yield better accuracy (but probably not to the
degree that DGPS can).

WAAS data, btw, is transmitted in the same BW (or
spectrum) as standard GPS signals - but from a
geosynchronous bird (actually a couple of them) ...

RF Jim


----- Original Message -----
From: "John Walshe" <John.Walshe@INPACTMICRO.COM>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Tuesday, November 19, 2002 11:52 AM
Subject: Re: [ot]: GPS differential corrections for home brewers??


> As far as I can make out it is a question of what accuracy you want. For
mm
> accuracy I'm sure Dr Hill's comment holds, but if you just want cm/m
> accuracy then a static/base unit in the locale of the area of interest
would
> be sufficient (it is likely to be using the same satellites anyway). I was
> using a Leika DGPS system just this weekend and the correction signal was
> beamed from a site in Wales (Holyhead ->I was mapping in the centre of
> Ireland ~250miles away!). The repeatability of the resultant map was quite
> good - enough to show that the mappers did take the same path when doing
the
> work. Of course when the differential signal was lost the plot jumped west
> by about 5m.
> I'm working on a system similar to your idea but because of the terrain I
> will have a centrally located unit, static and just logging position (this
> should wander with the dither). The second (mobile)unit for the mapping I
> will carry with me and at the end of the day I'll subtract one data set
from
> the other to get (hopefully) a more accurate map (and hopefully zeroed on
> the static location to boot). I only need 1~2m accuracy so I'm hoping that
> will do.
> I'd be interest to hear your - or anybody else's comments on my proposal.
>
> John
>

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