Author Topic: My Bad Coordinates  (Read 5759 times)

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GopherGreg

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My Bad Coordinates
« on: January 05, 2013, 17:19:53 »
Most of you who have found my caches know that the coords are usually off by quite a number of meters. I have a few that are okay, but my last few, ( The All-Stars of 2012-2013 (GC43EBJ), Dotted and Crossed (GC43BC6), Geocash3(00)fun (GC41QK3), and one other, Each digit Twice (GC424YW) ) have been off by ten, fifteen, and maybe even twenty meters. It annoys me, which is bad enough, but its even worse that I waste cachers time on a difficulty '1.5' cache because they're looking in a tree 15 meters from the cache...

I use a Magellan EXplorist GPS, but my coords still seem to be off! I do everything I can: I usually take three or four coordinates, and average that, but my coords are still off. Usually its hard to average with my GPS, because the coordinates are bouncing around. Like if I have a cache, and I take three waypoints for the cache, I have to average something like: N45 18.098: N45 18.104: N45 18.079. It gets to a point where picking the middle of all of those numbers doesn't give you an average as much as you're guessing. I'd really like to find a GPS that isn't super expensive, but that can average coords a bit better. I hate finding caches that have bad coordinates, they frustrate me; so I'd rather not frustrate others with my coords as well. Any suggestions here? Thanks,

GopherGreg

GopherGreg

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Re: My Bad Coordinates
« Reply #1 on: January 05, 2013, 17:24:36 »
Oops... I should have put this in the GPS units section...

hidnseek

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Re: My Bad Coordinates
« Reply #2 on: January 05, 2013, 19:42:23 »
how long do you let the unit settle when on location?   which explorist do you have?


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GreyingJay

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Re: My Bad Coordinates
« Reply #3 on: January 06, 2013, 00:00:44 »
As you have discovered, there are many factors that weigh in to GPS coordinate accuracy.

Sky cover is one factor. On a very cloudy day, or under heavy tree cover (or worse: under heavy tree cover on a very cloudy day) your GPS struggles to get a clear signal from the satellites overhead. Cedars are particularly bad due to their dense leaves. The more satellites your GPS has a lock on, the better your coordinates will be. Taking a reading on a sunny clear day is probably going to yield better results than if you're in the middle of a snowstorm.

More advanced GPS units support coordinate-correction technologies such as WAAS. If yours supports this, it will help improve accuracy as well. Units with larger or more advanced antennas are also more likely to get better GPS reception. The good news is that, other than WAAS support, most GPS units today offer pretty much the same level of accuracy.

Turn the GPS on well before you get to GZ. The longer it is on and working, the better your coordinates will be. Don't walk to GZ and then turn on your GPS and take a reading. Have it on the whole time.

You say you already do coordinate averaging. That's good. Remember you need to be patient with averaging. Set the GPS unit down and let it "settle". Give it a good 5 minutes to sit there first. Then, take a bunch of readings at regular intervals and write each one down. Throw away the "biggest" and the "smallest" number and average the rest. This is called removing the statistical outliers. In your example, you provide 3 numbers: 104, 079, and 098. If those were real GPS readings, I would agree they are pretty "jumpy". That 79 looks out of place compared to 104 and 98. And I would want more than just 3 data points to average.

If those were real GPS readings, I would conclude that reception wasn't very good today and keep taking readings for a few more minutes. Take a reading, say, once every 30 seconds for the next 3 minutes. Say you get more numbers: 104, 079, 098, 100, 102, 097, 097, 097, 098. I would throw away the 79 (and probably the 104 too) and average the rest of the readings that you get (works out to about 098). Very important to sample regularly and include the repeated readings! Over time you will develop a sense, so if you keep watching your coordinates hover around 97, 98, then you learn to do a sort of weighted average in your head, and when you see 94, you will give it less importance. The more samples you can include, the more accurate it becomes and the outlying data eventually becomes statistically insignificant.

Another trick which I often recommend is taking your own coordinates, and then using them another day to "find" your own cache. See where the arrow points. If it's misleading, then take another reading of the real GZ and take another average.

Finally, consider that larger containers hidden in "obvious" geo-spots (like a large hollow stump, or the crotch of a large tree) can make up for bad coordinates. Nobody cares that it's 10 meters off because they see the obvious spot and say "oh, it must be there". Especially for a lower difficulty cache.

I would be more than happy to help beta-test coordinates if you like.

Don't be discouraged and don't take it personally. Many cachers have caches with "off" coordinates. My Moondance coordinates were 20 meters off for several years. (Oops.)
« Last Edit: January 06, 2013, 01:00:31 by GreyingJay »

BlackRose67

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Re: My Bad Coordinates
« Reply #4 on: January 06, 2013, 00:47:03 »
If your GPS has the ability to average a waypoint, definitely use it.

I did a quick Google search and there may be an option called "set accurate position" when you create a new waypoint.
This seems to be how the eXplorist GPS units average a waypoint.

My GPS (Garmin eTrex 20) is the middle model of Garmin's entry level units and supports the GPS and GLONASS satellites, plus it also supports WAAS that GreyingJay mentioned.

I didn't start using WAAS until I was out with Keeper Of Maps on GAG18 night/morning back in October, but it seems to have helped reduce my frustration levels when hunting for tricky hides. 

Whenever I place a cache or am scouting out a possible location for one, I set my GPS right where the cache would be and let it perform waypoint averaging until it hits 100%.  I haven't had any complaints about bad coordinates of the hides I've done so far.

GopherGreg

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Re: My Bad Coordinates
« Reply #5 on: January 06, 2013, 08:41:03 »
If your GPS has the ability to average a waypoint, definitely use it.

how long do you let the unit settle when on location?   which explorist do you have?

I use the eXplorist GC (the green one) from magellan. It doesn't have a setting to average waypoints, as far as I know, and I've looked at every single setting on that GPS
Sky cover is one factor. On a very cloudy day, or under heavy tree cover (or worse: under heavy tree cover on a very cloudy day) your GPS struggles to get a clear signal from the satellites overhead. Cedars are particularly bad due to their dense leaves. The more satellites your GPS has a lock on, the better your coordinates will be. Taking a reading on a sunny clear day is probably going to yield better results than if you're in the middle of a snowstorm.
I have taken my coordinates at different times, but they all seem to be off. Some of my coordinates that people complain about the least have been taken during a cloudy day. My multi cache I mentioned, (GC43EBJ), when I first took its coordinates (three times!) It was cloudy, with a light snow. I came back the next day, because I was in the area, and took three more coordinates, this time, there was almost no clouds, just a few, if any. I averaged just the first set, then just the seconde set, then the whole two sets, and checked to see the better on Google Maps. The whole set seemed to be better, but according to sens-eh and geonerding were still off by twenty meters. The coords they gave me seemed to be better, but were still, (apparently) ten meters off. My GPS did fall out of my pocket once, onto concrete, but it has not done anything else to suggest there is something wrong with it: Is it just the type of GPS I have, or did dropping it really do something to just the coordinates that it takes?

Thanks guys,

GopherGreg

bluelamb03

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Re: My Bad Coordinates
« Reply #6 on: January 06, 2013, 12:05:51 »
Quote
Finally, consider that larger containers hidden in "obvious" geo-spots (like a large hollow stump, or the crotch of a large tree) can make up for bad coordinates. Nobody cares that it's 10 meters off because they see the obvious spot and say "oh, it must be there". Especially for a lower difficulty cache.

There's the best advice for hiding a cache! Your numbers could be 20 meters off but no one will mention it if they arrive at the GZ and "That's where I would put it!" and there it is! An obvious hide, an explicit description or hint, an easy to see container (NOT another micro in a tree!) and everyone enjoys the find.

The frustration arises when there's a thousand possible hides within 20 meters and the cache is nowhere near the solved GZ.

Blue -
Without shared stories we are strangers.
- Sheila Mendonça


GopherGreg

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Re: My Bad Coordinates
« Reply #7 on: January 06, 2013, 12:16:27 »
Quote
Finally, consider that larger containers hidden in "obvious" geo-spots (like a large hollow stump, or the crotch of a large tree) can make up for bad coordinates. Nobody cares that it's 10 meters off because they see the obvious spot and say "oh, it must be there". Especially for a lower difficulty cache.

There's the best advice for hiding a cache! Your numbers could be 20 meters off but no one will mention it if they arrive at the GZ and "That's where I would put it!" and there it is! An obvious hide, an explicit description or hint, an easy to see container (NOT another micro in a tree!) and everyone enjoys the find.

The frustration arises when there's a thousand possible hides within 20 meters and the cache is nowhere near the solved GZ.

Blue -

I know sometimes my hides are different, in odd places that people wouldn't put it usually, (GC3HH27), but I would still like my coordinates to be as close as I can get them. I place alot of micro hides, because there isn't mush room around Kanata for 'smalls', or any thing bigger. I have tried placing six or seven caches in the Hazeldean woods, but all of them are to close to Shutterbug, or a few mystery puzzles in there. Most of the caches in Kanata are in the area of where I want to place a geocache with a size other than 'micro', but all of these cache are abandoned by their owners, and need maintenance, that doesn't look like its going to happen. I fixed up shutterbug for gilligan_and_the_blue_noser, then let him know that I had the original container, that he needed to pick it up, and that my conatiner wasn't too sturdy, and was just a makeshift container till he did something. Then, I offered to adopt it, but there was no replies to my emails. Its the same case with 'Lazy Dog' by pyshic camel. Its needed maintenance for a while, but he hasn't done anything with his caches for ages. Since these caches are lying around the wooded area of kanata, I don't have much place to put a cache other than micro, so I'd prefer my coords are on for those caches. If I was placing a 'small',' medium', or 'large', I'd still rather my coordinates were on, but it wouldn't be as bad as if they were 20 meters off a cammoed bison tube in a pine tree, when the area has ten, or fifteen pine trees...

GreyingJay

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Re: My Bad Coordinates
« Reply #8 on: January 06, 2013, 14:36:40 »
Good on ya (as the Aussies would say) for offering to take care of abandoned caches and for trying to keep the standard of the game up. The whole community benefits from that.

You are right, abandoned caches are annoying. They take up space for no good reason. You were right to contact the owner to offer help. But if they don't respond, don't feel bad about posting a "Needs Maintenance" log. If even that gets ignored, after a few weeks of waiting, go ahead and post a "Needs Archived" log. This will attract the reviewers and if they agree with you that it looks like the cache has been abandoned, it will be disabled, and eventually archived.

I did it with Burt's Bees 2 in Kanata. After 9 months of no finds and lots of DNF's, I contacted the CO and posted notes, then left a NM log, then tried to contact the CO personally twice, then posted NA. A month later it was archived. I tried my best and the CO did nothing so I don't feel bad about it. That spot is now open if you want to put something out ;)

Xira

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Re: My Bad Coordinates
« Reply #9 on: January 06, 2013, 21:14:05 »
The user manual for the Magellan Explorist GC is available at: http://support.magellangps.com/support/assets/manuals/Magellan_eXploristGC_UserHandbook.pdf.

On page 16, it indicates that you should use "add geocache" to capture your current location.
On page 17, it says how to use it. Step 2 seems to be the important step.

Adding a Geocache
1. Press MENU and select ‘Add Geocache’ from the Options menu.
2. Wait approximately 2 minutes while the receiver uses ‘waypoint averaging’ to calculate an
accurate position. The bottom of the “Add Geocache” screen will display the estimated accuracy
when it is done averaging.
3. To change the name, highlight the Name field and press ENTER. Use the keyboard to enter the
desired name.
4. To change the Difficulty, Terrain, or Size move the highlight to the desired field. Use the joystick
left or right to change the setting.
5. Press MENU and select ‘Save’ to save the geocache.

bluelamb03

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Re: My Bad Coordinates
« Reply #10 on: January 07, 2013, 09:58:38 »
Many thanks Xira! Yes, the 'averaging' feature is what is needed here. That and a good satellite lock with adequate reception.

I'm not sure about the accuracy of these Magellan units, the antenna looks similar to the tiny 'patch' antenna the old Garmin eTrex units had - they would get squirrelly as soon as you got under tree cover!

I've noticed people putting disclaimers on their cache pages recently, for example "Spice Me Up" by hockeyboy4 http://coord.info/GC43F63:
Quote
Note that the coordinates have been taken by the geacaching iPhone app so have an accuracy of 5 meters.
It's not the 'app' that gives you accuracy, it's the antenna on the unit and the quality of the chipset in it!

As far as I'm concerned any co-ordinates taken with a SmartPhone are questionable until proven otherwise.

Blue -
Without shared stories we are strangers.
- Sheila Mendonça


GreyingJay

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Re: My Bad Coordinates
« Reply #11 on: January 07, 2013, 10:54:00 »
As far as I'm concerned any co-ordinates taken with a SmartPhone are questionable until proven otherwise.

I agree.. I've found hundreds of caches with my iPhone as my sole GPS device, but I still bring out the Garmin when I hide caches or need to do more advanced work like saving breadcrumbs. I wouldn't trust the iPhone GPS coordinates, based on some of my experiences with the phone/Geocaching app when in poor coverage -- sometimes the GPS meter will bounce pretty severely, or lock up altogether, or point me away from the target. These little glitche don't happen very often but they happen enough to make me distrust the app sometimes. And you can get lulled into a false sense of confidence when the phone sometimes gives you "coordinates" based on cell tower triangulation instead of an actual GPS lock.

GopherGreg

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Re: My Bad Coordinates
« Reply #12 on: January 07, 2013, 17:38:45 »
The user manual for the Magellan Explorist GC is available at: http://support.magellangps.com/support/assets/manuals/Magellan_eXploristGC_UserHandbook.pdf.

On page 16, it indicates that you should use "add geocache" to capture your current location.
On page 17, it says how to use it. Step 2 seems to be the important step.

Adding a Geocache
1. Press MENU and select ‘Add Geocache’ from the Options menu.
2. Wait approximately 2 minutes while the receiver uses ‘waypoint averaging’ to calculate an
accurate position. The bottom of the “Add Geocache” screen will display the estimated accuracy
when it is done averaging.
3. To change the name, highlight the Name field and press ENTER. Use the keyboard to enter the
desired name.
4. To change the Difficulty, Terrain, or Size move the highlight to the desired field. Use the joystick
left or right to change the setting.
5. Press MENU and select ‘Save’ to save the geocache.


That is what I did for my last cache 'Dotted and Crossed'. The coordinates were still off by twenty meters, maybe fifteen, even though I waited 2 minutes. I will try again, Thanks!

Good on ya (as the Aussies would say) for offering to take care of abandoned caches and for trying to keep the standard of the game up. The whole community benefits from that.

You are right, abandoned caches are annoying. They take up space for no good reason. You were right to contact the owner to offer help. But if they don't respond, don't feel bad about posting a "Needs Maintenance" log. If even that gets ignored, after a few weeks of waiting, go ahead and post a "Needs Archived" log. This will attract the reviewers and if they agree with you that it looks like the cache has been abandoned, it will be disabled, and eventually archived.

I know that I should post a note, and I think I will, but the cache does already need maintenance. The owner esponded to my first email, and said that I should fix up the cache, but didn't respond to any thing else. I know he isn't active, but it still feels wrong that I told him I'd fix up his cache, when I really throw out a container for a couple of months, request an NA, then come by and pick up the container once the cache is archived...

kirok

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Re: My Bad Coordinates
« Reply #13 on: January 07, 2013, 18:16:57 »
Hmmm.  Your issue may be that your Datum is set incorrectly.  Seems odd to me that you seem consistently off by 15 to 20 meters, even with averaging your coordinates.

You need to ensure that your Datum is set to WGS 84

Here's the section you need from your manual (page 25):

Selecting the Map Datum
1. Access the Tools menu and select ‘Settings’.
2. Highlight ‘Navigation’ and press ENTER.
3. Highlight the ‘Map Datum’ field and press ENTER.
4. Use the joystick (L/R) to step through the various map datums.
5. Highlight the desired map datum and press ENTER.
6. Press BACK.





GreyingJay

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Re: My Bad Coordinates
« Reply #14 on: January 07, 2013, 21:28:08 »
Oooh, nice catch Kirok! I'd forgotten about datum...