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Author Topic:   Garmin Differential GPS
Don88outrage posted 01-23-2008 04:26 PM ET (US)   Profile for Don88outrage   Send Email to Don88outrage  
I'm still using a Garmin 815 differential GPS, was just wondering with no selective availability in use by the government now does the unit still require a differential antenna to provide optimal accuracy. I'm guessing, it being an older unit there's probably some dependency on the differential signal within the unit's software. Goal would be to eliminate the antenna if possible. Appreciate anyone's feedback on experience with this question.
jimh posted 01-23-2008 04:30 PM ET (US)     Profile for jimh  Send Email to jimh     
The accuracy of your position will have greater precision if you use the Differential GPS receiver to augment the basic GPS receiver.

If Selective Availability Mode were turned on again, would it spoil the Differential GPS correction?

Chuck Tribolet posted 01-23-2008 06:57 PM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
Garmin 815? I don't remember it, Garmin's website doesn't
mention it, and Google can't find it.

GPS with SA on: about 300' accuracy.
GPS with SA off: about 45' accuracy.
GPS with differential (SA on or off): about 15' accuracy.
WAAS GPS: about 9' accuracy.

So, yes, it still helps. But essentially all modern GPS
receivers are WAAS-capable. Time for a new toy.

When WAAS came online (and Garmin nicely had a firmware
update to use it), I gave my DGPS receiver away to some folks
who were mapping trails in Henry Coe State Park that were down
in canyons where the WAAS birds of that day didn't reach,
but the DGPS did.

The US military has some localized disruption capability for
GPS the eliminates the need for SA.


Chuck

Don88outrage posted 01-24-2008 12:40 PM ET (US)     Profile for Don88outrage  Send Email to Don88outrage     
Thanks, that's about what I was thinking, the accuracy for the Long Island Sound area is very good, it will consistently find the same locations within 3 meters, have heard the differential signal is strong for the area. Chuck, you're right, how about a 215-D, and yes will be looking at the new toys at the upcoming shows.

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