How accurate should my GPS be?

[+Deep Search]

I have an emap, and it gets me close (sometimes) but the other day I found the cache and the unit said I needed to go another 8 feet. One day it says 320 ft left so I go left, then 473 right??? Never found, Cloudy day maybe?I know its old and lamer than some but how much better could I have it? Within a reasonable price range. Do the newer ones actually pinpoint the spot? I haven't dared going for nanos or minis to avoid the frustration. I know the fun is the hunt but I'm willing to upgrade if it's worth it.

[jmundinger]

The owner's manual for my Vista HCx says that I can expect less than 10 meter accuracy 95% of the time and less than 3 meter accuracy 95% of the time when WAAS is enabled. But, the accuracy information also includes a footnote that indicates that the accuracy can degrade when the Department of Defense has activated its selective availability system. Also, remember that when you are looking for a cache, your are dealing with the error in your unit as well as the error of the unit of the person who hid the cache. My suggestion would be to search for a couple of benchmarks - the coordinates for those should have a smaller margin of error than the average cache. I am not familiar with the emap. But, if you are consistently within 15 feet, that's probably all that you can reasonably expect from a consumer grade gpsr.

[Motorcycle_Mama]

The accuracy listed on the spec sheet for that model is 15 meters (49 feet).

 

Modern receivers can be accurate 5 - 10 meters or so.

 

However, since both the hider's GPS unit and the finder's GPS unit might be off by 20 feet or so each, even with a modern receiver, you won't necessarily be pointed to the EXACT spot.

Edited January 19, 2008 by Motorcycle_Mama

[+J10fly]

Tree cover, miserable day, anything can play into how accurate it is. GPS is good to get you close but then you have to use some geocaching skills to find GZ. I have a $300 GPS that is really nice, and I had a $100 GPS that actually got me closer than this one, but you start to learn the GPS "personality" of how close it is or isn't. There are none that are 100% accurate, keep in mind, the hider may also have a slightly different coordinate too when he placed the cache.

[+Barrettg]

Tree cover, miserable day, anything can play into how accurate it is. GPS is good to get you close but then you have to use some geocaching skills to find GZ. I have a $300 GPS that is really nice, and I had a $100 GPS that actually got me closer than this one, but you start to learn the GPS "personality" of how close it is or isn't. There are none that are 100% accurate, keep in mind, the hider may also have a slightly different coordinate too when he placed the cache.

Deep,

 

My family and I are g'cachers. We use a Garmin eTrex Vista HCx. It draws a pretty tight circle around the cache. 3 to 5 meters depending on conditions.

 

Last week-end, we went to Newport RI and did the Cliff Walk. We searched for 5 caches. Found 4 of them. The 5th was a wash out. Not because of the GPS. We were on it like dots on dice. Instead, the clue was vague.

 

If you can get within 10 to 15 feet of a cache, and if the clue(s) are good enough, you'll find the cache all day long. Between your GPSr and the person who placed the cache, their GPSr is going to be off a little, you'll get it, believe me.

 

Good Luck,

the G Man

[+Deep Search]

Thanks for all your answers. I was turned on to caching and just happened to have this old emap from years ago. And after going out with the person who got me interested in caching they said that it was because of the "map format " of the unit, that it was not going to work well for this. I will get a new one soon but I do appreciate all your help and I will keep at it with this relic for a while.

[baozebub]

WAAS corrects for satellite ephemeris and clock errors; and ionospheric delay errors. WAAS cannot correct for bad GPSs (faulty receivers or slow processors). On a bad iono day, WAAS performance degrades. Another factor that degrades performance is satellite geometry. In deep canyons, the satellites you see tend to be right overhead, which results in weak lateral positioning. Satellite geometry that is heavily weighted on one side or another will also give you bad lateral positioning. In general, a full constellation will give you the best positioning. A non-cloudy day may not necessarily mean a good ionospheric clear day, so GPS performance may degrade for no visible reason (this should be rare).

 

The quality of your hardware and software is very important in determining your position. A person with a bad GPS unit on a bad iono day may be off by quite a bit.

 

I've got a Vista HCx and love it!

[phern47]

When I want to pinpoint a location and save it as a waypoint, my IFinder Pro has a function called "averaging". When I go to enter a waypoint, I can choose this function and just wait a bit. The IFinder Pro indicates how many points it has in it's memory. The longer I stay where I am, the more points the IFinder records. It takes about 10 or 15 seconds to have about 30 points. When I choose "create", the IFinder averages out all the points before creating my waypoint.

 

Today, I tried out the function on a waypoint that had 30 points before being averaged out. I was ice fishing and wanted to find a fishing hole that I had used the day before. The snow and wind had wiped out all traces of the hole but I got within a few feet of it and with careful scrutiny, I could see the disturbance in the snow where my previous fishing hole had been made.

[phern47]

Thanks for all your answers. I was turned on to caching and just happened to have this old emap from years ago. And after going out with the person who got me interested in caching they said that it was because of the "map format " of the unit, that it was not going to work well for this. I will get a new one soon but I do appreciate all your help and I will keep at it with this relic for a while.

 

The EMap is a nice unit. It even has mapping. I have noticed that the older GPS units seem to have fewer problems than the newer units. Look at all the messages concerning the problems people are having with their new GPS units. If your EMap has worked well so far, it will work well for a long time to come....it's dependable and well worth keeping. If you do buy a newer GPS unit some day, keep the Emap as a back up or as a loaner.

[+spyderman]

I have an emap, and it gets me close (sometimes) but the other day I found the cache and the unit said I needed to go another 8 feet. One day it says 320 ft left so I go left, then 473 right??? Never found, Cloudy day maybe?I know its old and lamer than some but how much better could I have it? Within a reasonable price range. Do the newer ones actually pinpoint the spot? I haven't dared going for nanos or minis to avoid the frustration. I know the fun is the hunt but I'm willing to upgrade if it's worth it.

I started with a Garmin 12 which belonged to my brother-in-law. Not long after I bought an E-Map and still have it along with four more units. The e-map is as accurate as any on given days. I use my e-map as a loaner to folks who want to try their luck at caching and most are and were pleased with it.

However it lacks some of the bells and whistles of newer models but I use it with GSAK and am still pleased with it.

[+spyderman]

I have an emap, and it gets me close (sometimes) but the other day I found the cache and the unit said I needed to go another 8 feet. One day it says 320 ft left so I go left, then 473 right??? Never found, Cloudy day maybe?I know its old and lamer than some but how much better could I have it? Within a reasonable price range. Do the newer ones actually pinpoint the spot? I haven't dared going for nanos or minis to avoid the frustration. I know the fun is the hunt but I'm willing to upgrade if it's worth it.

Would you consider selling it ?

[+Deep Search]

Thanks for all your answers. I was turned on to caching and just happened to have this old emap from years ago. And after going out with the person who got me interested in caching they said that it was because of the "map format " of the unit, that it was not going to work well for this. I will get a new one soon but I do appreciate all your help and I will keep at it with this relic for a while.

 

The EMap is a nice unit. It even has mapping. I have noticed that the older GPS units seem to have fewer problems than the newer units. Look at all the messages concerning the problems people are having with their new GPS units. If your EMap has worked well so far, it will work well for a long time to come....it's dependable and well worth keeping. If you do buy a newer GPS unit some day, keep the Emap as a back up or as a loaner.

 

Super! Thanks for your input.I will keep on truckin.

[+Deep Search]

I have an emap, and it gets me close (sometimes) but the other day I found the cache and the unit said I needed to go another 8 feet. One day it says 320 ft left so I go left, then 473 right??? Never found, Cloudy day maybe?I know its old and lamer than some but how much better could I have it? Within a reasonable price range. Do the newer ones actually pinpoint the spot? I haven't dared going for nanos or minis to avoid the frustration. I know the fun is the hunt but I'm willing to upgrade if it's worth it.

Would you consider selling it ?

 

I don't really do enough to justify replacing this one if I don't have to. I have a lil babe strapped to my chest most days when I go out with my 10 year old. so we are very low key, and don't get out much. I wish I had found this hobby a few years ago, I do love it. However if I do decide to sell it, I will let you know. Thanks.