What is EPE?

[cwoper]

Can anyone explane this to me?I know that it has to do with accuracy,how can I use this?What does EPE stand for.It is on my position screen,however there is no mention about in my manual.

[GRANDMASTER CACHE]

That's your Estimated Position Error, usually in feet. It's a reference to how many feet (plus/minus) you are from being accurately placed to your reported coordinates. HTH

 

If you hide it, they will come.

Grandmaster Cache

Tank at: FISH WHISPERER'S LAGOON

[yeahright]

Took me awhile to figure this out previously.

 

Estimated

Position

Error

 

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.

[GRANDMASTER CACHE]

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.

 

If you hide it, they will come.

Grandmaster Cache

Tank at: FISH WHISPERER'S LAGOON

[dsandbro]

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.

[cwoper]

You guys are awesome,thanks Dudes!!! cwoper

[Kerry.]

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 everybody keeps telling me where to go

[+BletchleyPark]

if I am not mistaken, if you HAVE to equate it with distance...20ft should be considered the radius and not the diameter of the "confidence circle". Thus, you could be up to 40ft away.

 

Correct me if I'm wrong, here.

 

BP

[+Seth!]

quote:

---

Originally posted by BletchleyPark:

Correct me if I'm wrong, here.

---

 

Okay.

 

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!

 

- Seth!