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GPSr accuracy - what to expect?


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I've been using a Geomate Jr. and the accuracy is great. I just got a good deal on a Garmin Colorado 300. I only had time to look for one cache but I wouldn't have found it with the Colorado. I followed the Colorado until it was showing I was a few feet, looked everywhere and couldn't find anything. I turned on the Geomate and it showed me 30 feet away, I walked directly to the cache. Standing beside the cache the geomate jr. showed 0 feet and the Colorado showed 32 feet. Pretty big difference. Is the Colorado defective? Is there a difference in the way they interpret the signals? I don't get it, how did my $50 GPS outperform the garmin by such a large margin?

I might try again tomorrow but I'm thinking of returning the Garmin.

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Also, see if the Colorado is set to use WAAS. The raw accuracy of the GPS system is usually not much better than 100 feet or so, due to atmospheric turbulence. There are ground stations that interpret the GPS signals to measure the amount of that inaccuracy and it gets sent with the GPS signal. However, with some GPSr, you have to turn it on.

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GPS signal accuracy, IMO, is highly dependent on the amount of signal scattering trees between the satellites sending the signal, and your GPSr. Thicker foliage, gives greater problems. On a boat on a lake, GPS signal reception and interpretation is fast and accurate.

 

It is also dependant on the software, chips (SIRF III is better) and antenna type (patch is ok, helix antenna is better).

Edited by chuckr30
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Is there a difference in the way they interpret the signals? Yes.

 

My old Legend is still the fastest and most accurate of all my GPSR's.

 

However....I love the functions in the new 62 unit. I love the paperless ability and the field notes.

 

The response is slower in ALL the new units, probably from all the added firmware, but they get to zero sooner or later. If I'm in a hurry, I turn WAAS off. If I need to get exactly to zero, I keep WAAS on.

 

You should have found the cache before you arrived at zero anyways.

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