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| Subject: | RE: GISList: Handheld GIS - WAAS and othe ACCURACIES |
| Date: |
08/21/2001 06:37:01 PM |
| From: |
Neil Havermale |
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A point on this accuracy thing.
With SA off the best "any" autonomous GPS receiver will navigate is by
definition 30 meters depending smoothness of the receiver - you may get like
15-20 meters some days. The reference to 2 to 5 meters is a differentially
corrected position - either by traditional DGPS sources like the US Coast
Guard or number of the differential suppliers... as well as for receivers
with WAAS capability - wide area augementation system. You can also do
+/-10cm accuracy with post processing methods for certain "carrier" and raw
data loggers.
The WAAS GPS receiver is the most exciting developement for GPS since we had
the full array in place. There is a whole new era of GPS receivers able to
provide the 2 to 5 meter accuracy ALL THE TIME by use of the WAAS. WAAS is a
FAA development for air traffice control and limited visibility stuff. Its
still a bit limited to horizon blockage (like trees, mountains, buildings
and the like) and generally works better in the West that East of the US.
It is not as yet avaialble out side ot the Northern Hemisphere as far as I
now know.
The WAAS differentials are currently broadcast from a single stationary
satellite. Another two are on their way in the next year or two. Expect over
time for WAAS enabled receivers to tighten their accuracies to sub-meter -
like 0.5 to 0.8 CEP as the FAA specs tighten and the receivers improve.
My understanding is most Trimble "recent" handheld and some of their other
receivers can be software updated to allow WAAS correction. You might also
look at Garmin as they have increasing offerings of GPS devices just along
the lines of your interest - maps, waypoints, triggers, and other stuff you
didn't know you might need. Rumor is Garmin will have a PDA/CELLPHONE/GPS
combo to release in early January. But don't let that slow your down.
Garmin has all the features your are looking for in a sub $400 12-channel
receiver "with WAAS" included. Some coarse street/highways maps are
included and more detailed street maps can be purchased as well.
http://www.trimble.com
http://www.garmin.com
http://www.magellan.com
FYI
MidNight Mapper
aka neil
-----Original Message-----
From: John Koles [mailto:micron@global.net.au\
Sent: Tuesday, August 21, 2001 6:58 AM
To: gislist@geocomm.com
Subject: Fw: GISList: Handheld GIS
Bryan,
Since President Clinton authorised turning off of SA these little handheld
Units can deliver positional accuracy of 2 to 5 meters most of the time.
----- Original Message -----
From: "Bryan Wolfenden" <bwolfenden@louisberger.com>
To: "John Koles" <micron@global.net.au>: "Charlene Howard"
<charlene_howard@mwcog.org>: "'Chris Coberly'"
<christopher.coberly@madisonriv.com>: <gislist@geocomm.com>
Sent: Tuesday, August 21, 2001 9:41 PM
Subject: Re: GISList: Handheld GIS
> I am curious as to what the accuracy of these small gps units would
> be? We have used a trimble pathfinder pro for submeter accuracy. >
>
> Bryan J. Wolfenden
> Senior Environmental Planner
> The Louis Berger Group, Inc.
> 295 Promenade Street
> Providence, RI 02908
> Tel. 401.521.5980 Fax. 401.331.8956
> Email: bwolfenden@louisberger.com
>
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