GPSMAP 62s vs PN-40 EPE

[+stigloc]

Having both GPSMAP 62s and a PN-40, I find it rather surprising that the PN-40 consistently shows a lower EPE than the 62s. When driving in my car, 62s usually shows EPE of 9, PN-40 of 7. When traveling down a valley, the 62s EPE will fluctuate greatly going from EPE of 8 to 17, while the PN-40 will go from EPE of 7 to 10. While walking in the woods, 62s EPE varies from 8 to 20, while PN-40 EPE may go from 8 to 10. Having said all of this, both GPSr will roughly put me in the same GZ. The 62s will acquire WASS quicker and retain it better than the 40. I had thought that the quad helix antenna would hold EPE better than the patch antenna. So does EPE mean nothing if both GPSr put you in the same area? I have a location adjusted benchmark that I would like to place both GPSr's to see if there is a difference between them and would like to hear if anyone else who has a GPSMAP 62s and notices that there EPE fluctuates as much as mine. If I had not owned a PN-40, I would have never paid much attention to it. ( 62s I keep upright and 40 horizontal )

[+embra]

One trouble with making EPE comparisons is that it's not clear exactly what they mean. Sure, they are Estimates of Position Error. But what are the methods of doing the estimation and what are the probabilities that your true position is within the circle defined by the radius of the EPE? 95%? 90%? 99%? It would seem that the EPE for a given GPS device offers meaningful comparisons to devices of the same model, but beyond that it's hard to know what contributes to the differences we see.

[+Team CowboyPapa]

And don't bother DeLorme and Garmin about obtaining the specific details on how they determine EPE until you get the recipe for Coca Cola.

[+user13371]

Which one do you want? Original Coca-Cola up to 1903 (9mg of cocaine per serving)? Or the cocaine-free variety basically unchanged since then? Or that funny 1985 detour called New Coke? Or any of the diet, caffeine free, or alternate flavored (lime, vanilla, cherry, etc) varieties?

 

I tells ya, there are as many Coca Cola formulae as there are for EPE numbers!

[+stigloc]

Which one do you want? Original Coca-Cola up to 1903 (9mg of cocaine per serving)? Or the cocaine-free variety basically unchanged since then? Or that funny 1985 detour called New Coke? Or any of the diet, caffeine free, or alternate flavored (lime, vanilla, cherry, etc) varieties?

 

I tells ya, there are as many Coca Cola formulae as there are for EPE numbers!

As I was saying, EPE's are over rated apparently.

[+user13371]

Ok, seriously -- EPE is not especially useful for comparing different devices to each other. I tend think of it more as the GPSR's own "confidence" in what it's showing me at any given moment. It's not saying "We're within 7 feet of this spot" with any kind of precision. It's saying "I reckon we're around here, but..." the EPE number tells me how fuzzy the guess is likely to be.

Edited November 9, 2010 by lee_rimar

[+dfx]

the only way to find out which one is more accurate is by doing a proper statistical comparison between the coords they produce.