Inaccurate cache coordinates

[+slate6715]

So lately I've been noticing that the caches I have the most trouble with are the ones greater than 20 feet off, according to my GPSr. Once you get beyond 20, the search area really starts to grow exponentially so if you're talking about a small or micro in a boulder field, we're talking many thousands of hiding spots. I find myself wanting to write grumpy logs for having had to spend so much time looking, but in the end I'm usually polite.

 

So I'm not sure how grumped out I should be on inaccurate coordinates. I mean, in a canyon I understand it'll be tough to get a good fix. However, when I have a clear view of the sky and both my GPSr agree on where the coordinate should be, I shouldn't find it 50 feet away. I figure if you're planting a cache that hundreds of people over several years are going to attempt, you should at least make the effort to take numerous measurements coming in from several directions with multiple GPSrs (if you have them) to ensure accuracy. I often also wonder if people deliberately put the coordinates off to make it more challenging. I appreciate an ingenious hide (like the one that looked like a yucca plant, or the one hidden in a non-functioning sprinkler head), but don't want to spend days perusing a boulder field in an ever-expanding arc. To me, the best part of Geocaching is the journey and final locale far more than the hunt.

 

So, my question for others, what do you think is reasonable error, assuming a fairly clear view of the sky? How do you handle posting on caches that are off--do you post an error correction (i.e. coords or direction/distance) or just let it go?

[+va griz]

It is frustrating when the cache is a long way off from where GZ "should" be. I try to remember that my visit to the cache site (at least the first one) is only one reading with my GPS. So it is at least possible that the owner took multiple readings over days and my reading could be the fluke.

 

Most of the time the coords put me within 5 to 15 feet, but until it gets over 30 I consider it normal noise.

[+Userzero]

So, my question for others, what do you think is reasonable error, assuming a fairly clear view of the sky? How do you handle posting on caches that are off--do you post an error correction (i.e. coords or direction/distance) or just let it go?

 

Accuracy depends on the number of satellites in the sky and their position relative to you.

 

My GPSr shows accuracy in the form of a circle around my position. Sometimes, the circle is fairly big, sometimes it is really tight. Add to that the error of the Cache Owner at the time he placed the cache, and that could add up to a pretty bad accuracy. Whether or not he used one or seven GPSr at that time is irrelevant, because the satellites are still in a bad position in the sky. Coming back later is a better way of getting a good average. Or leaving your GPSr at Ground Zero for a few hours, and then averaging the track it has made is a pretty good way also.

 

So it's not always the Cache Owner's fault. If I find a cache that was way off, I simply say so neutrally in my log. If there are many such comments in the log, the CO should update his coordinates himself, in my opinion.

Edited September 15, 2008 by Userzero

[+DanOCan]

Once you get beyond 20, the search area really starts to grow exponentially so if you're talking about a small or micro in a boulder field, we're talking many thousands of hiding spots. I find myself wanting to write grumpy logs for having had to spend so much time looking, but in the end I'm usually polite.

 

On those sorts of caches I tend to write subtle hints in my logs such as:

 

"So many places to hide such a small cache here -- really wish there had been a good hint to consult before the hunt got tedious." (Assuming there wasn't a useful hint already.)

 

"A cache this small in a location like this could likely have another star added to the Difficulty rating." (Assuming the Difficulty wasn't already accurate.)

 

And, if all else fails I'll log a DNF and put the cache on my Ignore list. The key thing to remember is once the hunt isn't fun anymore it is time to walk away and look for a different cache.

[+briansnat]

I'm happy with anything under 50 feet off. I probably won't even make a mention of bad coords in my log until

it is about 75 feet off. Hey, for all I know the coords are great and my GPS is off.

[+StarBrand]

Average error on most of our handheld units is in the 20 - 25 foot range. Add the hiders and the finders potential errors together could be 40 or more. I used to get upset long ago but have come to understand that 30-40 foot off is really not unusual and nothing to worry about.

[+wimseyguy]

Anything inside of 50' is acceptable to me. It's possible that there is the extreme example of both the hider's 25' of inaccuracy and mine being linear.

 

But I agree that needle in haystack hides deserve good hints, and I always walk away when it isn't fun to search any more. I spent 45 minutes looking for one micro in the woods yesterday, and walked away from another location after 7 minutes. Logged DNF's on both. <shrug>

[+wimseyguy]

..and sometimes posting in the forums is so much fun I do it twice.

Edited September 15, 2008 by wimseyguy

[+ArcherDragoon]

I'm happy with anything under 50 feet off. I probably won't even make a mention of bad coords in my log until

it is about 75 feet off. Hey, for all I know the coords are great and my GPS is off.

 

Average error on most of our handheld units is in the 20 - 25 foot range. Add the hiders and the finders potential errors together could be 40 or more. I used to get upset long ago but have come to understand that 30-40 foot off is really not unusual and nothing to worry about.

 

Anything inside of 50' is acceptable to me. It's possible that there is the extreme example of both the hider's 25' of inaccuracy and mine being linear.

 

But I agree that needle in haystack hides deserve good hints, and I always walk away when it isn't fun to search any more. I spent 45 minutes looking for one micro in the woods yesterday, and walked away from another location after 7 minutes. Logged DNF's on both. <shrug>

I was going to write something here...but all three seemed to have covered this very well

[Skippermark]

Here in CT, coords are "good" if they're within 20 feet. 30 is even okay. 40 isn't even that bad. 50 starts getting iffy, but we won't usually say anything until it's over 60 and then we'll just mention that our GPS was playing tricks on us and wanted us to be here...

 

Forgot to say that in some places, like FL & CA, we found the coords to be much more accurate, usually 10 feet or less. Those areas were very flat and open with large views of the sky. Here where we live, there are lots of hills and rock ledges. That, combined with metals and stuff in the ground makes the GPS signal "bounce" around a lot more, making it a little harder to get an accurate signal.

Edited September 15, 2008 by Skippermark

[+Harry Dolphin]

And sometimes 47 feet can be an unnecessary error. If I'm caching in the woods, that's a bit off. But when I'm in the city that can be bad. Coords and map said northeast corner of Kingsbridge and 238th. No hint available. After logging the DNF, I noticed some finders mentioned that it was on the northwest corner. Not good.

[+johnling]

I have found more often than not that the accuracy of placed caches depends on each owner. The owner that hits GZ right on does so on all of his hides. Another on is always off by approximately the same distance on all of his hides. I attribute this to the owner having a high sensitivity receiver or not. When I get to a cache I always look at who placed the cache. I then know right away weather the cache will be at GZ or if I am going to have look around more.

 

We just had a long time cacher place a 26 cache series in a large loop around town. Many of them are LPC’s and GZ has been dead center between 2 or three Lamp Poles. I have assumed this was intentional as way to make a simple LPC a little bit of a challenge or time consumer.

 

I placed my caches on clear sky days with an accuracy of 8 to 11 feet on the GPS and checked cords several time to be as accurate as possible. Not everyone does this. Maybe the day they planned to place their hides turned out to be a cloudy and/or rainy day. Maybe their GPSr is less accurate. Maybe they used the wrong datum.

 

I have started using CacheMagnet for cachers that always seem to be a bit off on their hide cords. It seems somewhat like cheating but in the Bird’s Eye View I know the area before I get their.

 

Just my 2 cents.

[+DanOCan]

I have found more often than not that the accuracy of placed caches depends on each owner.

 

Yeah, same here. There are certain cache owners where I simply know to focus my search at ground zero regardless of where the logical hiding spots are because their coordinates are always solid. For some other cachers I have been know to say the following:

 

"Admit it, the posted coordinates were taken from where you threw this cache out of the window of your car, aren't they?"

[+Mocadeki]

I'm happy with coords that are within 50 feet. With my old gps I remember thinking being within 50 feet of a cache in the woods was very good. Before than when we used the Garmin legend in the woods it was luck whether we'd have cache location. I don't mention the coords being off until they're more than 50 feet off.

[+Wild Thing 73]

As the other person says......I just try and take a fix....average the satilites signals for about 10-15 minutes. close it out...walk away and try the signal again. ....Then, I get a log from a cacher saying that the signals are loose or in error, or, words to that effect. I hope that cacher will place his correct Cord's in the log, but mostly they don't, so next time I'm in the cache area, I will recheck the Cord's....It is the right thing to do....I hate loose Cord's, which means sloppy cache placement...We must all be concerned Geocachers. Happy Trails and looking a GZ all the time...

[rogheff]

I thought I'd chime in here. I'm that person who's caches always seem to be way off. When I hide a cache in the woods, it's a real "treat" trying to get satelite reception let alone accuracy. I spend a long time wandering around just trying to get reception.

 

I usually cache with a 25' accuracy on my GPSr. On a bad day, I may get 48'. Sorry, not much I can do about that except try everything I can to get the coords as accurate as possible. I'm still at the mercy of the GPSr.

 

I've met cachers on teh trails while looking for my caches. Once a good friend of mine was hunting for one of mine with his GPSr hanging from a branch at his GZ. I envied the fact that he got reception under the tree canopy. The container itself was 64' away from his GZ. It was about 16' away from my GZ on THAT day.

[+johnling]

I thought I'd chime in here. I'm that person who's caches always seem to be way off. When I hide a cache in the woods, it's a real "treat" trying to get satelite reception let alone accuracy. I spend a long time wandering around just trying to get reception.

 

I usually cache with a 25' accuracy on my GPSr. On a bad day, I may get 48'. Sorry, not much I can do about that except try everything I can to get the coords as accurate as possible. I'm still at the mercy of the GPSr.

 

I've met cachers on teh trails while looking for my caches. Once a good friend of mine was hunting for one of mine with his GPSr hanging from a branch at his GZ. I envied the fact that he got reception under the tree canopy. The container itself was 64' away from his GZ. It was about 16' away from my GZ on THAT day.

 

That's all part of the fun. At first I did have to wonder if the cache was there or not. As I cached more I began to pick up on these things.

[+slate6715]

Speaking of GPSrs and accuracy, I have noticed a big difference between my two GPS. The Garmin eTrek is quite accurage on the plains of Colorado without a tree in sight but just doesn't handle tree canopy very well--even holding my hand over the antenna is enough to make it lose signal. My Garmin Forerunner 305 (and the 205 when I had it), I can practically be underground and still get signal. I find the Forerunner 305 will come within 15 feet on -most- caches, perhaps 20% of them are beyond 20 feet off. On one of the caches we own, I usually come within 5 feet of it with the GPS when I go to maintain it. I recently did an 11 point multi--and did find the points were either smack dab on, or about 25 feet to the south, nearly consistently. So I'm wondering if those caches that are off are one of two things:

 

- Based on the sensitivity of the GPS, quirks that skew it one direction or another routinely

- Drive-by planting (i.e. not taking averages of multiple measurements, etc)

 

I personally have never noticed constellation playing a huge difference, however if half the sky is blocked by a cliff or mountain, it does tend to pull my readings the other direction slightly. Sit in a canyon and interesting things happen. However, not to say you couldn't have a bad luck day where just not many satellites are above you or they're mostly on one side of the sky giving you bad triangulation.

[Skippermark]

While on the subject of accurate coords, Keystone has a great post about getting good coords. This is how we've been doing it all along, and most everyone says are coords are "spot on."

[Clan Riffster]

One of the caches in my favorites list has a concrete span above the sidewalk. As I approached GZ with my old Magellan SporTrak Color, I watched my distance counting down to about 5' away. This was near the edge of the span. Two more steps showed the cache 160' away. This patten kept repeating itself, and led to a couple DNF's. In an attempt to figure this out, I switched to the satellite view screen, observing that the listed satellites changed significantly after I stepped under the span. When I came back for my third attempt, I had my 60CSx, which was not affected by the span.

[Motorcycle_Mama]

I thought I'd chime in here. I'm that person who's caches always seem to be way off. When I hide a cache in the woods, it's a real "treat" trying to get satelite reception let alone accuracy. I spend a long time wandering around just trying to get reception.

 

I usually cache with a 25' accuracy on my GPSr. On a bad day, I may get 48'. Sorry, not much I can do about that except try everything I can to get the coords as accurate as possible. I'm still at the mercy of the GPSr.

 

I've met cachers on teh trails while looking for my caches. Once a good friend of mine was hunting for one of mine with his GPSr hanging from a branch at his GZ. I envied the fact that he got reception under the tree canopy. The container itself was 64' away from his GZ. It was about 16' away from my GZ on THAT day.

I thought I'd chime in as a response to this.

 

I'm not trying bash you, but there's is a LOT you can do to get more accurate coordinates when hiding caches. Not hiding caches in locations where your current equipment has limited satellite reception comes to mind.

Edited September 16, 2008 by Motorcycle_Mama

[+Seeker625]

Personally I think if the co-ords put me within 20 feet I can take it from there. I do get a bit peeved when someone posts new co-ords for one number differences. For instance the last number was 664 and someone put a correction of 665. A GPS will be off that much on a good day, To say nothing of having a different brand than the one that was used to place the cache. I have been watching one cache that has been corrected 3 times and all within one number of the others.

[rogheff]

I thought I'd chime in here. I'm that person who's caches always seem to be way off. When I hide a cache in the woods, it's a real "treat" trying to get satelite reception let alone accuracy. I spend a long time wandering around just trying to get reception.

 

I usually cache with a 25' accuracy on my GPSr. On a bad day, I may get 48'. Sorry, not much I can do about that except try everything I can to get the coords as accurate as possible. I'm still at the mercy of the GPSr.

 

I've met cachers on teh trails while looking for my caches. Once a good friend of mine was hunting for one of mine with his GPSr hanging from a branch at his GZ. I envied the fact that he got reception under the tree canopy. The container itself was 64' away from his GZ. It was about 16' away from my GZ on THAT day.

I thought I'd chime in as a response to this.

 

I'm not trying bash you, but there's is a LOT you can do to get more accurate coordinates when hiding caches. Not hiding caches in locations where your current equipment has limited satellite reception comes to mind.

 

You're limiting me to sunny hilltops (and then I will get 16' of accuracy). The very last cache I placed was on a sunny hilltop with no trees within 100'. I had 176' of accuracy that day. I had a heck of a time getting accurate coords. I use the mapping/imaging programs to get me even closer. It's kinda hard to find hidey holes on sunny hilltops by the way.

[Skippermark]

One of the caches in my favorites list has a concrete span above the sidewalk. As I approached GZ with my old Magellan SporTrak Color, I watched my distance counting down to about 5' away. This was near the edge of the span. Two more steps showed the cache 160' away. This patten kept repeating itself, and led to a couple DNF's.

We had something like this happen while caching in downtown Boston.

 

We were doing a cache in a pocket park and walking towards the cache. Our GPS started counting down, 150', 140, 130...we continued walking, but then suddenly it stopped around 110' and was basically spinning the arrow around in all random directions. We were never able to get closer than 110', so we finally went back to about 150 feet away and walked and noticed where the arrow wanted us to be and tried to estimate where 110' would put us. The cache was in hand a short bit later.

 

If we hadn't found it, I was going to walk 150' away and do it again from a different direction to try to triangulate where it was. The only thing I could think was causing it was either the tall buildings, or maybe some metal underground or something like that.

[+Konshentz]

Unless it's like 75 feet, I don't mind the coords being a little off. I get bored when I walk right up to it and can see it without really searching. I also hate people that leave logs that complain, when it was probably their awful GPS that caused the screw-up.

[+edscott]

With all these stories about how tough it is to get good coordinates with a GPS I wonder if maybe I really am cheating by not using one.

[+GrateBear]

For the few caches I have placed, I take multiple readings and average them, then go to Google Earth to see how accurate that is. Doing so usually works quite well. The only problem is when the GE picture is old, such as when streets aren't in the picture yet.