# gps 76 accuracy circle

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here is the deal. my epe is inside 15ft but when i use the measure distance function to measure the accuracy circle, it reads 140ft. what is going on? i thought epe was a radius measurment. anybody know?

did we find it?

Estimated Position Error, it is nothing more than ESTIMATED and for many reasons does not mean that because the EPE is so many feet then that is the actual accuracy relative to the actual position.

Cheers, Kerry.

I never get lost everybody keeps telling me where to go

But Kerry, I think the ''Acuracy Circle'' IS suppose to be a visual version of the EPE. Why it would differ, I don't know.

quote:
Originally posted by EraSeek:

But Kerry, I think the ''Acuracy Circle'' IS suppose to be a visual version of the EPE. Why it would differ, I don't know.

As it was written above I read the "measure distance function" as basically the distance from the GPS position to the target

Whichway, could you also clarify things.

Cheers, Kerry.

I never get lost everybody keeps telling me where to go

the "measure distance" function lets you measure between points. in this case i measured from current position on the screen to the edge of the accuracy circle(radius) and multiplied by two.

did we find it?

If it's a garmin receiver you're using, the accuracy circle is a combination of the EPE and estimated map error on the mapping units. I'm not exactly sure how they compute it, but you'll see the size of the circle changing with both EPE changes, and the type of map you've loaded. The circle tends to be pretty big with the basemap.

One thing to keep in mind is that the circle, and the EPE numbers are just semi educated guesses as to the real accuracy. It may or may not reflect reality at any given time.

For what it's worth

Jeff

If you zoom in on different maps, you'll see the text "mapsource" under the scale ruler change to "overzoom". At what scale that happens gives a measure of how accurate the particular map you use is. It will be different for the basemap or the MetroGuide, for example.

That in turn is reflected by the size of the circle that's shown on the map display.

Anders

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