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Please Help With The Accuracy? Circle!


Durango!

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Posted

My GPSr has a circle on the map view I'm sure you are all familiar with. It basically shows the zone of uncertainty, and as you zoom in really close, you will see it appear. If the GPSr is accurate to only 20 feet, and you are zoomed in to the level where your screen shows 20 ft across, the accuracy circle will be about as big as the screen. Well, the circle on my unit is staying really big, it shows at about 0.2 miles and doesn't change. It is hard enough to explain this, can anyone help me out with what is going on?

Posted
Well, the circle on my unit is staying really big, it shows at about 0.2 miles and doesn't change. It is hard enough to explain this, can anyone help me out with what is going on?

I would suggest you reset the unit and see if that helps. What GPSr are you using?

Posted

What mapping software do you have loaded? As I recall the accuracy circle is linked to the mapping software that is loaded in the unit. The base map is not very accurate and the circle is large to reflect this inaccuracy. With MG or CS loaded the unit should respond the way you think it should.

Posted
Well, the circle on my unit is staying really big, it shows at about 0.2 miles and doesn't change. It is hard enough to explain this, can anyone help me out with what is going on?

The "accuracy circle" is supposed to show that your actual position after taking into account both GPS measurement errors *and map errors* is probably somewhere within the circle *as shown on the map*.

 

So if you only have the rather coarse basemap on your GPS the accuracy circle will always be shown very large since there can be large mapping errors. Load a more accurate map and the size will decrease. With identical GPS measurement errors, the accuracy circle will be largest with the basemap, smaller with Roads & Recreation, still smaller with US Topo, MetroGuide or City Select.

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