Re: questions about accuracy

From: Sam Wormley (swormley1_at_mchsi.com)
Date: 11/19/04 

Date: Fri, 19 Nov 2004 20:17:18 GMT

PM wrote:
> I have a Garmin V that can achieve 7' accuracy on the external car ant. A
> farmer friend of mine tells me about using GPS to plant, apply chemicals,
> etc. The way he explains it the hardware/software he is using would have to
> be a lot more accurate than 7'
>
> Is it just because the consumer GPS devices are just not that accurate to
> hold the prices down? Can anyone shed some light on this or direct me to a
> site that can.
>
> Thanks.
>
>

How do you know Garmin V that can achieve 7' accuracy?
   http://edu-observatory.org/gps/gps_accuracy.html

DGPS is the bread and butter of the professional GPS community. Mapping,
minning, precision agriculture, survey (sub cm), and a host other applications.
See: http://www.edu-observatory.org/gps/dgps.html

Differential GPS involves the cooperation of two receivers, one that's
stationary and another that's roving around making position measurements.
The stationary receiver is the key. It ties all the satellite measurements
into a solid local reference. Here's how it works:
   http://www.trimble.com/gps/dgps.html
                                               -- Trimble Navigation Ltd.

See: http://www.edu-observatory.org/gps/dgps.html

Some Differential Reference Datums

   Source* Reference URL (supporting)
_________________________________________________________________________________
   Omnistar NorthAm NAD-83 Ref: http://www.omnistar.com/faq.html
   Omnistar World WGS-84 Ref: http://www.omnistar.com/faq.html
   Racal-Landstar WGS-84 Ref: http://www.bruttour.com.au/DGPS.html
   WAAS WGS-84 Ref: http://users.erols.com/dlwilson/gpswaas.htm
   USCG Beacon NAD-83 Ref: http://users.erols.com/dlwilson/gpswaas.htm
   CORS NAD-83** Ref: http://www.ngs.noaa.gov/CORS/metadata1/

*There are many other sources used around the world that I have not included
**Referenced to ITRF00