🚀 go-pugleaf

In article <1992Oct2.193224.12784@CSD-NewsHost.Stanford.EDU>, vadim@CS.Stanford.EDU (Vadim Akselrod) writes:
|> I'm planning to incorporate a Global Positioning System and a Digital
|> Compass into a wheeled robot for improved navigation.  If anyone is familiar
|> with vendors that market either a GPS or such a compass, I would love to
|> hear about it!  Thanks in advance!

For GPS-based navigation, it really depends on how much you are
willing to spend for accuracy. If you can live with GPS without SA
(i.e., approx. 25 meters), then a number of manufacturers carry
"cheap" units. These units are being sold primarily to the recreational
aviation and marine markets by Trimble, Navstar, Maganox, etc. A good
source for vendors is "GPS World" magazine. 

If you want better accuracy than 25 meters, you can setup a fairly
cheap differential GPS system which will give you around 2 meter (or less)
accuracy. Of course, you need to setup a GPS base station which can
broadcast DGPS corrections to the vehicle (typically done with low
power UHF/VHF radios). The best (i.e., "cheapest") solution for mobile
vehicles is:

	Base Station:	Navstar XR4-G   (approx. $2500)
	Remote Station:	Trimble Placer GPS 300 (approx. $1250)
	UHF/VHF radios: approx. $2000

Of course, you can get better than 25 meter accuracy with regular GPS
(i.e., surveyors routinely get centimeter accuracy), if you are
willing to sit a position and wait a while. For real-time (i.e. near 1
Hz) updates, however, you really need DGPS.

As for digital compasses, well, I've been looking... If anyone has
pointers to some, I'd love to hear about them! So far, the only thing
I've found is the KVH C100 "Compass Engine" (basically a flux-gate
compass with some electronics). It costs approx. $700 and will give
0.5 degree heading accuracy.

-Terry
NASA Ames Research Center

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