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JROFam

Coordinates always off?

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I've noticed with 2 Garmin GPS receives that the cache locations are usually off by sometimes up to 20'. Newer caches seem to be prone to this problem, older ones from 8 years ago seem to be better. Is this by design or is it possible that people creating the caches are not getting an accurate reading? I know that my unit, Garmin GPSMap 66st, is pretty accurate.

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I would expect any Garmin device to be reasonably accurate.  There could be a number of issues, which include a clear view of the sky, the type of GPSr used to obtain coordinates, and the skill of the hider to use it correctly.  If the coordinates appear significantly off, like on the order of 30 feet or more, I would probably mention it in my log.  If enough people get the same results, it might provoke the CO to update the coordinates.

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28 minutes ago, JRMFam said:

I've noticed with 2 Garmin GPS receives that the cache locations are always off by a bit. Is this by design or is it possible that people creating the caches are not getting an accurate reading? I know that my unit is pretty accurat.e

 

How much is "a bit"? Under ideal conditions, when the GPSr is receiving clear signals from its full complement of satellites, the best you can hope for is about 10 feet of uncertainty and when you add in the same uncertainty for the cache setter you can easily double that. Throw in some buildings, tree cover, hills or go down in a steep gully and the accuracy can degrade considerably. I've also seen phone apps do oddball things, like only taking readings spasmodically - I've seen examples when taking coordinates for waypoints in a multi where the phone shows the same coordinates for positions twenty or thirty metres apart because it hadn't taken a fresh reading at the second location.

 

I currently own an old Garmin GPSmap 62s and a much newer Oregon 700, and I've noticed when I have both out in the field, in some places they're essentially in lock-step of each other whereas in other places they can consistently show a difference of six or seven metres - presumably one antenna configuration is more susceptible to reflected signals than the other in certain situations.

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2 hours ago, JRMFam said:

I've noticed with 2 Garmin GPS receives that the cache locations are always off by a bit. Is this by design or is it possible that people creating the caches are not getting an accurate reading? I know that my unit is pretty accurat.e

 

Everyone swears their newfangled/ultra-modern gizmo is accurate to a flea's butt.      ;)

 - But civilian GPS on it's best day is around ten feet in "accuracy".  That hasn't changed since 2000...

What are the odds you and the CO had "best days" when at GZ ?

The other 2/3rds prefers her iphone, while I use a GPSr.  We're rarely more than 12' apart (and that is okay).

When you reach close, best to put the GPSr away and start looking.    :)

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2 hours ago, cerberus1 said:

 

 - But civilian GPS on it's best day is around ten feet in "accuracy".  That hasn't changed since 2000... 

 

 

That is incorrect.  WAAS use results in a typical accuracy of about 3 meters with a reasonably dlear view of the sky.

 

WAAS was officially turned on July 10, 2003.

 

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9 minutes ago, fizzymagic said:
2 hours ago, cerberus1 said:

- But civilian GPS on it's best day is around ten feet in "accuracy".  That hasn't changed since 2000... 

 

 

That is incorrect.  WAAS use results in a typical accuracy of about 3 meters with a reasonably dlear view of the sky.

 

WAAS was officially turned on July 10, 2003.

 

Um, three metres is about the same as ten feet, isn't it? WAAS isn't available in this part of the world but I can still get about 3 metres accuracy in a good spot with a clear view of the sky.

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6 minutes ago, barefootjeff said:

 

Um, three metres is about the same as ten feet, isn't it? WAAS isn't available in this part of the world but I can still get about 3 metres accuracy in a good spot with a clear view of the sky.

 

Yep.  I did pretty much that well in NZ last year.

 

My objection is to those who say that 3 m is the *best* you will ever see in a consumer GPS, and that 10m is more realistic.  I can't remember the last time my GPS was off by 10 m, and I don't even use a fancy Garmin.

 

10 feet, in the USA, is the accuracy you should *expect* with your consumer-grade GPS.

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10 hours ago, barefootjeff said:

I currently own an old Garmin GPSmap 62s and a much newer Oregon 700, and I've noticed when I have both out in the field, in some places they're essentially in lock-step of each other whereas in other places they can consistently show a difference of six or seven metres - presumably one antenna configuration is more susceptible to reflected signals than the other in certain situations.

My friend has a 62s and I have a 64s. We will usually 'zero out' pretty close to each other, but in maybe 20% of the time, we will zero out 30-40 feet apart. As we search over 15-20 minutes, we usually end up pretty close again. We both have WAAS enabled. I have turned GLONASS on and off but have not seen that it makes any difference in how often our handhelds agree or not. Given enough time, the devices eventually 'settle' pretty close to each other.  I suspect that the filtering/averaging firmware might be slightly different. The antennas look the same, but you're right that they could be a little different under the cover, too. 

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I would say that some are off up to 20 feet or so; this is out on a trail with no buildings and some are in dense forests while some are not so dense. Some caches are dead on as well. I should have clarified, not ALL caches are "way" off, just some recent ones in the past couple of years and maybe that's due to people creating caches on their phones. 

 

When one creates a cache, what's the "rule"? Are you to bring the person RIGHT to the spot or in the close vicinity so that they have to look around? Just curious as I want to keep that in mind and I also realize that some people may not record an averaged waypoint when creating a cache. 

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16 minutes ago, JRMFam said:

When one creates a cache, what's the "rule"?

Do the absolute best you can with coordinate accuracy.  Do NOT post deliberately loose coords, "so that they have to look around?" thanks for asking.

 

Here's relevant guideline section

Before submitting a cache page

  • Get accurate GPS coordinates.
    • GPS usage is an essential element of hiding and seeking caches.
    • The cache owner must visit the geocache location to get accurate coordinates with a GPS-enabled device.
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12 hours ago, Touchstone said:

If the coordinates appear significantly off, like on the order of 30 feet or more, I would probably mention it in my log. 

 

+1

 

Post the offset and the bearing.  But if there are previous logs about the coords being "right on", it may be just you. B)

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10 minutes ago, JRMFam said:

I would say that some are off up to 20 feet or so; this is out on a trail with no buildings and some are in dense forests while some are not so dense. Some caches are dead on as well. I should have clarified, not ALL caches are "way" off, just some recent ones in the past couple of years and maybe that's due to people creating caches on their phones. 

When one creates a cache, what's the "rule"? Are you to bring the person RIGHT to the spot or in the close vicinity so that they have to look around? Just curious as I want to keep that in mind and I also realize that some people may not record an averaged waypoint when creating a cache. 

 

Years ago some had issue with phones, but these days, a cache placed using a phone has no difference (that we've seen) in "accuracy".

By the Help Center, we're supposed to provide coordinates to a container or object. 

That some may be a little off doesn't mean they were only bringing you to a general area. :)

For example...

A couple years ago, a new guy would state on every cache page that his GPS showed the cache was off 6-to-whatever feet.

The other 2/3rds met him one day, and she asked if he'd stop at an event (I had a coin for him too) with us.

 I don't remember what it was called, but they had that "place your flag at the coordinates" game. 

Winner closest to the coordinates (a "hidden" washer on the ground IIRC...) got a lock n lock, loaded. 

 - That's when he realized that pretty-much everyone was "off".      :D

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46 minutes ago, cerberus1 said:

That's when he realized that pretty-much everyone was "off".      :D

 

+1

 

Especially in forest areas, the vast majority of caches I've found are nowhere near “zero” in distance. I walk over there, it's what, “50 feet from here” and counting down. Yet I see the container next to a nearby tree. Unless I take the time to let the GPS settle down, and unless there seems to be an actual problem with the coordinates, I don't even mention the “accuracy” in this case. I found it. It's good.

 

But for my caches, over the weeks or months before I submit one for publication, I've checked my readings many times.  I get it as close as I can.

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2 hours ago, JRMFam said:

I should have clarified, not ALL caches are "way" off, just some recent ones in the past couple of years and maybe that's due to people creating caches on their phones. 

 

I'm one of those "newbies" who cache with my phone, usually using the geocachng app, and have had success in finding nearly 1300 caches in less than 2 years.  My husband and I have also hidden a few, with only one issue with coordinates being off, and on that one our original coordinates are still the posted ones as only one cacher seemed to have an issue.

 

For hiding a cache, using our phones, we both take a few readings at a potential cache site, coming from different directions, so we have 6 or more readings.  Then we come back another day with the coordinates we feel are "best" (usually the day we hide the cache; we use our potential coords to see where we end up).  I also use Google earth on my laptop at home to see where it lands on a satellite map, and I use the sat map on the phone as well.

 

If we find a cache where the posted coordinates are more than 30 feet (10 meters) for BOTH of us, we'll note that.  Sometimes our readings will differ, and we'll both search in different places.  Sometimes he finds it, sometimes I find it.  Sometimes we'll both be led to the same area.  I've gotten in the habit of putting the phone away if I get within 15 - 20 feet, and just LOOKING.  Hints and previous logs get re-read if we don't come up with it after a few minutes; generally I've read the description and hints and a few logs prior to attempting a cache.

 

We've tossed around the idea of a "real" GPSr unit, but our phones and the official app (and a Wherigo app or two) work just fine for the caching we have done so far.  As far as caches placed by newbies being "off",  I think it's more likely due to their inexperience, not so much the GPS device  being used.  The GPS and mapping built into today's phones amazes me; we use traffic maps quite a bit and they are very accurate as to where you are and how long it'll take to get to where you are going!  And caching is no different; we've found our phones to be more than adequate for our little hobby, both finding and placing caches for others to find.

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1 hour ago, CAVinoGal said:

 

I'm one of those "newbies" who cache with my phone, usually using the geocachng app, and have had success in finding nearly 1300 caches in less than 2 years.  My husband and I have also hidden a few, with only one issue with coordinates being off, and on that one our original coordinates are still the posted ones as only one cacher seemed to have an issue.

 

For hiding a cache, using our phones, we both take a few readings at a potential cache site, coming from different directions, so we have 6 or more readings.  Then we come back another day with the coordinates we feel are "best" (usually the day we hide the cache; we use our potential coords to see where we end up).  I also use Google earth on my laptop at home to see where it lands on a satellite map, and I use the sat map on the phone as well.

 

If we find a cache where the posted coordinates are more than 30 feet (10 meters) for BOTH of us, we'll note that.  Sometimes our readings will differ, and we'll both search in different places.  Sometimes he finds it, sometimes I find it.  Sometimes we'll both be led to the same area.  I've gotten in the habit of putting the phone away if I get within 15 - 20 feet, and just LOOKING.  Hints and previous logs get re-read if we don't come up with it after a few minutes; generally I've read the description and hints and a few logs prior to attempting a cache.

 

We've tossed around the idea of a "real" GPSr unit, but our phones and the official app (and a Wherigo app or two) work just fine for the caching we have done so far.  As far as caches placed by newbies being "off",  I think it's more likely due to their inexperience, not so much the GPS device  being used.  The GPS and mapping built into today's phones amazes me; we use traffic maps quite a bit and they are very accurate as to where you are and how long it'll take to get to where you are going!  And caching is no different; we've found our phones to be more than adequate for our little hobby, both finding and placing caches for others to find.

 

It could be that people are not paying attention or getting accurate readings. I really think that part of it is the device though as well. I've used a lot of devices, phones, GPSr, etc and always found that GPSr is better, just my personal preferences, I suppose. I just really like the Garmin 24k Topo maps- I find that they have so much more data than Apple or Google maps when it comes to the woods. I just my unit for more than caching as well. 

I did notify the cache owner about the coords, some of them others have posted that they are off as well. When I placed my 2 caches, they were exact but the actual contained was well hidden.

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5 hours ago, kunarion said:

 

+1

 

Post the offset and the bearing.  But if there are previous logs about the coords being "right on", it may be just you. B)

 

Or the cache may have moved.   I have a cache which was found by a group of 8-10 cachers.  All of them mention that the coordinates were off, but none of them provided coords where they found it or a direction/bearing which would have help locate a container that someone had moved from it's original hiding spot.  

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6 minutes ago, NYPaddleCacher said:

Or the cache may have moved.   I have a cache which was found by a group of 8-10 cachers.  All of them mention that the coordinates were off, but none of them provided coords where they found it or a direction/bearing which would have help locate a container that someone had moved from it's original hiding spot.  

Yep.

We had one similar.  Moved back n forth from one part of a bridge structure to the other, roughly 16'.

Maintenance becoming an issue, so now it's placed elsewhere, and  it can't "move" without someone doing it on purpose.   :)

 

An ammo can was moved on purpose, when a new person (Intro app)  thought the coordinates were off, and placed it "where their GPS said it should be".

 - Why they'd think it should be left out in the open, alongside a trail,  well, the other 2/3rds never got a reply to that one ...

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23 hours ago, kunarion said:
On 12/8/2018 at 9:14 PM, Touchstone said:

If the coordinates appear significantly off, like on the order of 30 feet or more, I would probably mention it in my log. 

 

+1

 

Post the offset and the bearing.  But if there are previous logs about the coords being "right on", it may be just you. B)

 

But if there's a good mix of accurate and inaccurate reports, it's quite likely that the general gps detection is rough in that area. Even a broken clock is right twice a day.

 

22 hours ago, kunarion said:

Especially in forest areas, the vast majority of caches I've found are nowhere near “zero” in distance. I walk over there, it's what, “50 feet from here” and counting down. Yet I see the container next to a nearby tree. Unless I take the time to let the GPS settle down, and unless there seems to be an actual problem with the coordinates, I don't even mention the “accuracy” in this case. I found it. It's good.

 

Yep, I love group caching like that with everyone's noses in their device, calling out their distance to gz. Then you find the cache and wait, stand on it. Listen to the readings. "5m here!" "2m here!" "15 here!" "I've got it right here!" meanwhile none of them could possible be right.

And that's why you hone your geosense, and especially in areas like that, put the device away when you're within a reasonable distance and start searching. In questionable places like that hopefully the hint is sufficient (for the D) to locate the container.

 

And as mentioned, there could be any number of reasons why coordinates may not be accurate to the container. You can only blame the device if you assume that everything is 100% ideal - no container drift, optimal signal conditions, sufficient skills of the hider, decent hider device, sufficient skill of the seeker, sometimes even a more precise gps coordinate itself (which is impossible to be more accurate than the standard given 3 decimal DDM format, which gives about 1.8m 'tiles' between digits).

 

If your device get more accurate than that, then averaging may get you a more accurate placement coordinate, but as soon as you drop them into GC you're reduced to 3 decimal minute format. Unless you provide higher accuracy coordinates in your cache description, finders will always be limited to the accuracy the standard DDM listing coordinates, no matter how accurate their device is.

 

21 hours ago, CAVinoGal said:

As far as caches placed by newbies being "off",  I think it's more likely due to their inexperience, not so much the GPS device  being used.

 

Absolutely this.

And likewise, I just crossed 12,000 finds, and only ever cached with iPhone (from 3GS, now with 8+).  The key is knowing your device and using it properly.

Today it's extremely unlikely that inaccuracies are due solely and unavoidably to the device itself.  But, some devices do make it easier to have accurate coordinates.

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Wellllll ... I still see folks offsetting their caches.  "I took my co-ords. at X but noticed a much better spot at Y".  Further, I know of finders pulling  the same caper

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To me 20' is acceptable but 40', 100', or more is not

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54 minutes ago, jellis said:

To me 20' is acceptable but 40', 100', or more is not

 

You're assuming that everywhere has good GPS reception but that's not always the case. One of my caches is in a narrow gully that has a very limited view of the sky such that it's rare to have more than five or six satellites visible at any one time. This is the spread of coordinates I got on four separate days when I was planning the cache:

 

GZSpread.jpg.ffb0b397f4bfe36a2d70a52cd3d138b8.jpg

 

The spread on these is about 15 metres or 50 feet, and the reading the seeker will get when attempting the cache will no doubt be different again. The best I could do was take an average and provide some helper photos and strong hints on the cache page.

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23 hours ago, barefootjeff said:

 

You're assuming that everywhere has good GPS reception but that's not always the case. One of my caches is in a narrow gully that has a very limited view of the sky such that it's rare to have more than five or six satellites visible at any one time. This is the spread of coordinates I got on four separate days when I was planning the cache:

 

GZSpread.jpg.ffb0b397f4bfe36a2d70a52cd3d138b8.jpg

 

The spread on these is about 15 metres or 50 feet, and the reading the seeker will get when attempting the cache will no doubt be different again. The best I could do was take an average and provide some helper photos and strong hints on the cache page.

 

There used to be a cache in one of the gorges in my town.  When I found it my GPS was telling me that it had 90' accuracy.   One of my hides can still be easily found if the coordinates were off by more than 100'.   It's in a tree in a field with no other likely places where a cache might be hidden within 200 feet.    I've also found (and DNFd) caches there were placed on a long metal fence where accurate coordinates are really important.      

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On 12/10/2018 at 7:51 AM, thebruce0 said:

If your device get more accurate than that, then averaging may get you a more accurate placement coordinate, but as soon as you drop them into GC you're reduced to 3 decimal minute format. Unless you provide higher accuracy coordinates in your cache description, finders will always be limited to the accuracy the standard DDM listing coordinates, no matter how accurate their device is.

And as a point of reference for those that haven't looked at what that means, it comes to about 6" for every 0.001 N/S, and at my 40d  latitude, about 4' for every 0.001 E/W. 

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On 1/17/2019 at 12:19 PM, barefootjeff said:

 

You're assuming that everywhere has good GPS reception but that's not always the case. One of my caches is in a narrow gully that has a very limited view of the sky such that it's rare to have more than five or six satellites visible at any one time. This is the spread of coordinates I got on four separate days when I was planning the cache:

 

GZSpread.jpg.ffb0b397f4bfe36a2d70a52cd3d138b8.jpg

 

The spread on these is about 15 metres or 50 feet, and the reading the seeker will get when attempting the cache will no doubt be different again. The best I could do was take an average and provide some helper photos and strong hints on the cache page.

 

That was the correct thing to do. 

 

Averaging measurements from different days gives you (most of the time) a better result than just using one measurement.

 

Thank you, even though I will never likely get a chance to find that one.

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17 minutes ago, ecanderson said:

And as a point of reference for those that haven't looked at what that means, it comes to about 6" for every 0.001 N/S, and at my 40d  latitude, about 4' for every 0.001 E/W. 

It's actually about 6 feet on the latitude, not 6 inches.

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This has been a question as long as there has been geocaching.

 

Expecting two GPS to have exactly the same ground zero at different times in unrealistic.

 

I suggest everyone using a GPS to try this little exercise, even though it costs a set of batteries. Turn your GPS on, set it somewhere it has a view of the sky and can stay for a while, clear the track log and then start tracking. Leave it there for at least 10 to 12 hours, and then look at your track log. You will find it looks like your GPS a=has been wandering all around. This is normal due to variations in the GPS satellites positions.

 

Usually the track will stay in a circle about 60 feet across, but sometimes there are glitches. My GPS once went from California to Oregon and back in less than a minute!

 

Your GPS is a navigation device, not a tracking device.

 

When you get within 20 feet or so, put your GPS away and start looking.

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10 hours ago, Dave_W6DPS said:

When you get within 20 feet or so, put your GPS away and start looking.

 

Sage advice.  Tough to follow sometimes - it would be much easier if the magic arrow did the hard work.

 

I got bent out of shape yesterday trying to find a cache exactly at the coordinates the GPSr indicated.  Looked around the bridge, got my feet wet trying to look under the bridge.  Called it off and posted a DNF, then went down the trail for another cache.

 

Then I went back by the same bridge on my way back to the car and just looked around, without GPSr in hand - and spotted it within a minute.  :rolleyes:

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