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[+CJOttawa]

I was caching over the weekend with a friend who I just helped buy a GPSr.

 

We're both pretty new to this but we came across one particular cache which seemed to have coordinates off by about 10 meters. (30 feet+)

 

Our GPSr's were getting about 3 meter accuracy and we couldn't locate the cache after about 20 minutes of crawling around the posted coordinates, looking high and low.

 

Ready to give up, I decided to walk down the trail and spotted a tree, with a rock leaning against it and well trampled vegetation around. Move rock - lo' and behold, a cache!

 

I stood there for a while holding the GPSr up high to get a good reading and marked the coordinates.

 

When I got back to my computer to log the find, I noted from the cache's photo gallery it appeared to be a different container but the hiding spot looked familiar (very likely where we found this cache).

 

I feel quite confident we took an accurate reading of coordinates on the cache. There's no mention of any offset on the cache page.

 

Coincidentally, I've visited some of this owner's other caches and not found them - now I wonder if all of his coords are off by some kind of predetermined distance!

 

I mentioned in my log the actual find coordinates and my confusion but I really don't want to seem like I'm whining to or about the owner.

 

Has this ever happened to you? What would YOU do in this type of situation?

[+owl&pussycat]

see post below - having comp issues.

Edited July 25, 2006 by owl&pussycat

[+gof1]

I usualy just mention in my log that my GPSr showed the cache X number of feet west (or east,etc.) of the posted coords. If the owner recieves several logs like that he knows his numbers could be off.

[+owl&pussycat]

I've noticed the same effect and oddly enough it seems to occur to caches that were place prior to the tsunami in SE Asia. If I am having difficulty finding a cache I tend to move 20-30 ft SE of 'ground zero' and then I find it. Also, if I am in trees or near large rocks there seems to be a definite bounce factor happening.

[+StarBrand]

I've noticed the same effect and oddly enough it seems to occur to caches that were place prior to the tsunami in SE Asia. ....

 

That should not have affected anything.... The effects would have been far more dramatic if it caused North America to shift by 30 feet.

 

Small consumer grade GPS receivers have a general accuracy of about 30 feet. Not surprising at all to find a cache inside the 30 foot radius of ground zero. The EPE reading on your display should not be read so literally. It is simply an estimate of the accuracy. I have read that the EPE reading has about a 75% confidence level from many manufactuers - not all that wonderful. Also imagine if your GPSr error was 3 meters and the hiders was also 3 meters than it could easily be 6 meters away.

 

I sometime mention if I find a cache 25 or more feet away but I don't make a big deal about it until it is more like 50 feet away or more. Less than 25 is not usually worth a mention.

[+briansnat]

Has this ever happened to you? What would YOU do in this type of situation?

 

It happens nearly every time I find a cache, so I would do nothing but log my find and thank the owner for placing a nice cache. 10 meters (32 feet) feet off is well within the expected margin of error. Your unit is accurate to from 3-10 meters and so was the unit of the the person who placed it (note: just because it says you have 3 meter accuracy it doesn't mean it does. It is just an estimate). So a cache that is 3-10 meters off is quite normal and even 20 meters (65 feet) off is not unusual.

 

I wouldn't even make mention of the coordinates in my log unless they were more than about 22 meters (about 70 feet) off.

Edited July 25, 2006 by briansnat

[rbrugman]

I usually don't mention it unless it's way off, because there are differences in the way GPSr's calculate the accuracy. My GPSMAP 60csx may be different than someone's explorist. It doesn't always mean mine is 100% correct and theirs sucks. Usually when placing a cache I use mine to average the coordinates and then I use a friends Magellan to test the coords. Changes in the season, tree cover and a bunch of other factors can make things less accurate. If the cache was placed before selective availability was turned off you're in for a much larger-scale hunt.

 

It's nice to make note of a "possible" inaccuracy.

[+StarBrand]

.........If the cache was placed before selective availability was turned off you're in for a much larger-scale hunt....

ummmmm - they ALL were placed after. It was in celebration of SA being turned off that the first cache was placed.

[+Harriet the Spy]

When I first being introduced to geocaching by my friend, he told me that when my gps says I have 40 feet left to go to start looking for signs of caching: Geowood, large stump that could hold an ammo can, geotrails, etc. Following this advice I have been able to find caches that have left some other cachers stumped. You are the search engine!

[4wheelin_fool]

Accuracy is important, and often overlooked by new cachers. Its entirely possible that your coords were off by 30 feet. However, 30 feet is usually the average for coords to be off. Put the accuracy indicator of your GPS on the same screen as the Distance to Go, and keep it in mind while looking. When I find a cache and the GPS says that it is still 50 feet away, I'll check the accuracy of the GPS, and usually it is 50 feet also. After standing in the same spot and letting the GPS settle, it may say 15 feet accuracy, with the cache 15 feet away. I try to get the accuracy to 9 feet when I hide a cache, but if someone else looks for it with their GPS saying 20 feet accuracy, then it is possible for the cache to be off 29 feet when they find it. See how it works? If you find the coords to be way off, just post new ones (unless it is a multi, or puzzle).

[+Tharagleb]

.........If the cache was placed before selective availability was turned off you're in for a much larger-scale hunt....

ummmmm - they ALL were placed after. It was in celebration of SA being turned off that the first cache was placed.

 

ummmmm - I think that was a joke.

[CacheNCarryMA]

If the cache was placed before selective availability was turned off you're in for a much larger-scale hunt.

 

Hey, I've got a cache like that.

[+Ichabod]

As others have pointed out, this is all part of caching and is certainly within the "normal" range of accuracy. I have noticed that there is sometimes a consistent difference in coordinates, depending on the manufacturer. I use a Garmin 60cs and there is a good local cacher here that uses a newer Magellan. On every one of his caches, my ground zero is always about 40 feet west of his ground zero. The North coordinate is always right on, however. It is very consistent, so I always know to move east when hunting his caches.

 

In my first 100 caches, small "innaccuarcies" in coordinates bothered me, but I have grown very used to it now and even hunt caches without my GPSr, which I find quite enjoyable. Sometimes the GPSr just gets in the way of good human instinct!

[+fizzymagic]

Has this ever happened to you? What would YOU do in this type of situation?

It happens nearly every time I find a cache, so I would do nothing but log my find and thank the owner for placing a nice cache. 10 meters (32 feet) feet off is well within the expected margin of error.

It's well within the margin of error for a cache placed in a forested area with only a few places around for the cache to be, where the hider doesn't take careful coordinates.

 

It's not within an acceptable margin of error for an urban microcache or a highly camoed cache. People in my area generally take good coordinates, so it is rare for me to read a distance greater than 20 feet from ground zero in areas with good reception. Under heavy tree cover, of course, the situation is completely different.

 

In this case, I would simply post the coordinates I took in my log, without any further comment. If they are better than the original coordinates, future finders will probably mention that and maybe the hider will update the coordinates to the ones you took.

 

One thing I have noticed: as the experience level of the hider increases, the coordinates tend to get better and better. That's to be expected, as people learn to use their instrument better and to take those good coords. So I take that into account as well when deciding whether to post additional coordinates or not.

Edited July 25, 2006 by fizzymagic

[+edscott]

Isn't the standard +/- 20 ft ???.. so with the two readings,.. hider + finder, it could be 40 feet and still be normal. The biggest deviation I have experienced was about 60 miles and I still found it. ..... OK it was a typo that soon got fixed, but it makes a good story.

[+edscott]

When I first being introduced to geocaching by my friend, he told me that when my gps says I have 40 feet left to go to start looking for signs of caching: Geowood, large stump that could hold an ammo can, geotrails, etc. Following this advice I have been able to find caches that have left some other cachers stumped. You are the search engine!

 

This system works for me also...

[+niraD]

The biggest deviation I have experienced was about 60 miles and I still found it. ..... OK it was a typo that soon got fixed, but it makes a good story.

I found one that was about 150' from my GZ once, but that's because I solved the puzzle incorrectly and didn't notice that my checksum was wrong.