Jump to content

What is EPE?


Recommended Posts

Took me awhile to figure this out previously.






I have this on my Magellan 315.

It equates to Garmins "Accuracy".


Gives you an idea of the accuracy range of the calculated position.


If I sit still, the display starts averaging, and I don't see an indication of accuracy until I start moving again.


Faster, Better, Cheaper

Pick any two.

Link to comment

Better yet, (now that you have what it "technically" means) here's a "real world" understanding:


If your EPE is say, 20' that means you could be 20' off when your GPSr shows you at being 0 feet away from your intended coords, or destination. So, if your EPE is at 20', and you are having trouble finding a cache, you could actually be around 20' from where it's actually posted. The lower your EPE, the greater your GPSr accuracy. icon_smile.gif


If you hide it, they will come.

Grandmaster Cache


Link to comment

Different manufacturers use different methods to determine EPE. A Garmin tech rep once emailed me back and said they use two standard deviations.


So there is still a 5% probability the error is larger than the displayed accuracy (or one in twenty waypoints)



Friends don't let Friends geocache drunk.

Link to comment

EPE (Estimated Position Error) with the emphasis on "estimated" as that's about exactly what it is, estimated, and next week with the next software revision it might be "estimated" a little different to what it was last week.


Just because it might say 20' really doesn't mean your in fact 20' from where ever as it's really ONLY an estimate and nothing factual in an absolute sense.


EPE is probably better treated as a relative measure in that 20' means the accuracy "might" be beeter than if it was displaying 30', basically 20' is a little better than 30' but not necessarily "really" 20' or 30 feet in the real world.


Cheers, Kerry.


Cheers, Kerry.


I never get lost icon_smile.gif everybody keeps telling me where to go icon_wink.gif

Link to comment

Originally posted by BletchleyPark:

Correct me if I'm wrong, here.


Okay. icon_wink.gif


Yes, it is the radius. But 20' still means 20' away, not 40'. However, here's the reality:


IF the person posted the genuine, honest-to-goodness 100% accurate coordinates and IF your accuracy (or EPE) was really and truly 20', then when your GPSr showed "zero feet", you could be sure that you were within 20 feet of the cache.


BUT the person who posted the cache ALSO had an EPE (or accuracy) of X. So let's say her or his EPE was also 20'. Now you may assume that you are within 40' of the cache. (e.g. the posted coords were 20' east of the actual spot and your GPSr has you 20' east of the posted coordinates.)


How's that for confusion?


I'd say that if your GPSr says "zero", you'd better stop looking at the GPSr and start looking for the cache! icon_biggrin.gif


- Seth!



Link to comment

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...