GPS accuracy test

[+TheAlabamaRambler]

GPS accuracy is a much-debated topic amongst geocachers.

 

Here's a test we can all perform that will give us some idea about GPSr's accuracy:

 

Have a family member or friend drive a nail in your yard when you are not there to see it and have them record the nail's coordinates. Tell them to push the nail far enough down that it can't be seen but that they can find it again. It's important that you don't know where the nail is or that knowledge will allow you to force the results.

 

Each day for a week have your GPS navigate you to those coords just as if you were finding an unknown geocache.

 

Place a numbered flag or stone where your GPS says is GZ each day.

 

At the end of the week have the hider reveal where the nail actually is.

 

Measure how far each of your markers is from the nail (true GZ).

 

Look at how widespread your markers will be!

 

I predict most folks will have at least one marker 50' from the GZ nail.

 

At the end of the week post a summary of your daily results here.

 

Again, if you know where the nail is that invalidates the test as you will unconsciously force the results to where you know they should be. Please don't waste our time with faked results to make some kind of point about how accurate your GPS is!

 

Post the model of your GPS, date, time of day and distance from true GZ for each day's marker.

 

If you have more than one GPS use different markers for each to avoid comparing the accuracy of multiple units.

 

Don't post the actual coords, we don't need to know where you live!

[+briansnat]

How do we know that the nail's coordinates are accurate?

[+Isonzo Karst]

It doesn't matter whether the nail's coords are accurate - I believe the point would be to demonstrate the spread.

 

As it happens we did a test at an event. A surveyor friend left a penny in the grass in a baseball field. We gave everyone coords and flags to place at the coords. The spread was very small, many many flags within the area defined by .001 degree. A few extreme outliers, probably from coords being loaded in error. Open sky.

[jholly]

How do we know that the nail's coordinates are accurate?

 

I think the point is not to find that the co-ordinates of the nail is super correct but how much the readings vary. We have events around here and one of the games is the GPS accuracy test. Much as TAR laid out. There is quite a variation of the flags around the pin.

 

But to take the co-ordinates of the pin out of the equation you can have your friend with the survey grade Trimble set the pin for you.

[+DragonsWest]

How do we know that the nail's coordinates are accurate?

 

In the words of Albert Einstein, "It's all relative."

 

The scatter will be the result of how the GPSr responds to the constellation of GPS satellites.

 

I've found mine can be amazingly stupid in the wide open, only able to register +/- 28ft and at other times have a higher degree of confidence in partial cover. While there are factors, such as signal reflection which can bamboozle the receiver, sometimes its down to sensitivity and how well the receiver works. Sometimes I've powered down out on the trail, then powered up again and found my unit working better. There's no calibration that I can find on the GPSMap 60c, so figure it establishes its internal reference values upon power-up. Could be powering up and letting it sit still in an open spot works better for some units. With my receiver only the Garmin engineers know for sure.

[+TheAlabamaRambler]

You won't know if the GZ coordinates for the nail are accurate, just as you won't know how accurate they are when you hide a cache.

 

Nor will you know during the test how accurately each marker is placed, since you won't know till the end where true GZ is.

 

As others have pointed out it's the spread of GZ readings that will occur over the week that will make this interesting.

 

I predict that the same user with the same GPS looking for the same coordinates each day will end up with seven markers at quite different directions and distances from the pin.

Edited April 26, 2010 by TheAlabamaRambler

[+cx1]

 

Again, if you know where the nail is that invalidates the test as you will unconsciously force the results to where you know they should be.

 

Won't the 1st flag you place basically cause the same error? Seems the tester would automatically start heading for the flag just as you predict the tester would start heading for the know location of the nail.

[+sbell111]

This seems like a completely pointless exercise.

[+sbell111]

You won't know if the GZ coordinates for the nail are accurate, just as you won't know how accurate they are when you hide a cache.

 

Nor will you know during the test how accurately each marker is placed, since you won't know till the end where true GZ is.

 

As others have pointed out it's the spread of GZ readings that will occur over the week that will make this interesting.

 

I predict that the same user with the same GPS looking for the same coordinates each day will end up with seven markers at quite different directions and distances from the pin.

Why is the nail even needed?

[+TheAlabamaRambler]

You won't know if the GZ coordinates for the nail are accurate, just as you won't know how accurate they are when you hide a cache.

 

Nor will you know during the test how accurately each marker is placed, since you won't know till the end where true GZ is.

 

As others have pointed out it's the spread of GZ readings that will occur over the week that will make this interesting.

 

I predict that the same user with the same GPS looking for the same coordinates each day will end up with seven markers at quite different directions and distances from the pin.

Why is the nail even needed?

Because the test is to see if your GPS will take you to the same place each time, and if not then how far off will you be each time, and the nail/pin/known location/target whatever you want to call it is the only way to know how different the reading is each day.

 

And if you think it is pointless, please don't do it!

[+dfx]

...

...

Each day for a week have your GPS navigate you to those coords just as if you were finding an unknown geocache.

this is where i'd have to abort that experiment. occasionally i can get to a spot where my GPS tells me <1 meters distance, but a few seconds later it will tell me that it's 2 or 3 meters away (or even more). so i could never pinpoint a specific location that my GPS considered to be "the spot".

[+supertech]

...

...

Each day for a week have your GPS navigate you to those coords just as if you were finding an unknown geocache.

this is where i'd have to abort that experiment. occasionally i can get to a spot where my GPS tells me <1 meters distance, but a few seconds later it will tell me that it's 2 or 3 meters away (or even more). so i could never pinpoint a specific location that my GPS considered to be "the spot".

 

Yes, but what is needed is more people to understand that their GPSr is not that acurate and to find a way to create a better GPS point when placing a cache. Here is where it gets interesting. If you performed this same kind of exersize on caches you are placing then the coords might be a touch more accurate.

 

Here's what I do. I set the GPSr tracking on with a new track, Then I leave the unit in place at the cache location for at least one hour. I do this on at least two different days and at different times. Then I use an average of the sets of readings as my coords that I post. I've only placed three caches, and only one is currnetly active, but that will change really soon. My goal is to have ten active within 10 miles of home.

 

thanks

 

Ken

[+sbell111]

You won't know if the GZ coordinates for the nail are accurate, just as you won't know how accurate they are when you hide a cache.

 

Nor will you know during the test how accurately each marker is placed, since you won't know till the end where true GZ is.

 

As others have pointed out it's the spread of GZ readings that will occur over the week that will make this interesting.

 

I predict that the same user with the same GPS looking for the same coordinates each day will end up with seven markers at quite different directions and distances from the pin.

Why is the nail even needed?

Because the test is to see if your GPS will take you to the same place each time, and if not then how far off will you be each time, and the nail/pin/known location/target whatever you want to call it is the only way to know how different the reading is each day.

The very fact that the person returns every day to mark a new spot will show him/her that the GPSr points to a different spot each time. There's no need to add a second person to the experiment. The nail is not needed because the individual will mark his initial spot on day one.

And if you think it is pointless, please don't do it!

Obviously, I will not be wasting my time in this manner. Edited April 26, 2010 by sbell111

[+DragonsWest]

I'm thinking this is a neat idea for a cache.

 

Place a bag containing green golf tees, with a sign explaining the exercise, near the cache and ask people to take one. At the very moment they spot the cache, place the golf tee in the ground, like near the toes of their right foot, push it all the way down so it is flush with the ground. Remember to place the cache exactly as you found it.

 

Then CO goes out after a month or first 30 finds and makes a chart, put it on the page and either continue the experiment or remove the tees and sign.

 

Anything for a new cache gimmick, eh?

 

Could also be a fun game for an outdoor event.

Edited April 26, 2010 by DragonsWest

[Whichwaydoigo]

...

...

Each day for a week have your GPS navigate you to those coords just as if you were finding an unknown geocache.

this is where i'd have to abort that experiment. occasionally i can get to a spot where my GPS tells me <1 meters distance, but a few seconds later it will tell me that it's 2 or 3 meters away (or even more). so i could never pinpoint a specific location that my GPS considered to be "the spot".

 

Yes, but what is needed is more people to understand that their GPSr is not that acurate and to find a way to create a better GPS point when placing a cache. Here is where it gets interesting. If you performed this same kind of exersize on caches you are placing then the coords might be a touch more accurate.

 

Here's what I do. I set the GPSr tracking on with a new track, Then I leave the unit in place at the cache location for at least one hour. I do this on at least two different days and at different times. Then I use an average of the sets of readings as my coords that I post. I've only placed three caches, and only one is currnetly active, but that will change really soon. My goal is to have ten active within 10 miles of home.

 

thanks

 

Ken

OK, Ken, but your effort to determine accuracy is not appreciated by cachers who don't spend the time to repeat what you did while they are looking for your caches. Again, common sense and visuals are the best advice when one nears GZ.

[+fizzymagic]

OK, Ken, but your effort to determine accuracy is not appreciated by cachers who don't spend the time to repeat what you did while they are looking for your caches.

Well, I appreciate it, which means you are wrong. But you are wrong mathematically, as well.

 

Improved accuracy in obtaining coordinates when hiding a cache results in less positional error or the finders looking for the cache. Hiders should always get the best coordinates they can for the cache location.

[+Setan Meyacha]

OK, Ken, but your effort to determine accuracy is not appreciated by cachers who don't spend the time to repeat what you did while they are looking for your caches.

Well, I appreciate it, which means you are wrong. But you are wrong mathematically, as well.

 

Improved accuracy in obtaining coordinates when hiding a cache results in less positional error or the finders looking for the cache. Hiders should always get the best coordinates they can for the cache location.

 

Although this sounds like an interesting experiment, if only to familarize yourself with your own GPSr, it is highly unlikely your method for hiding a cache will result in someone else finding it any quicker than taking an average of three readings on the same day. Not eveyone is using your particular GPSr and even if they are using the same model they will, more than likely, end up with a different GZ than what you obtained. That's just the nature of the beast. I have to agree that once you arrive 'near' GZ, use common sense, your knowledge of how that person hides their caches (as a rule, if you've found other caches hidden by that person) and, lastly, your GPSr to get you as close as possible.

Might suggest that experiment at one of our next events just to show how each person will come up with a different GZ; thanks for the tip.

[+Prime Suspect]

You won't know if the GZ coordinates for the nail are accurate, just as you won't know how accurate they are when you hide a cache.

 

Nor will you know during the test how accurately each marker is placed, since you won't know till the end where true GZ is.

 

As others have pointed out it's the spread of GZ readings that will occur over the week that will make this interesting.

 

I predict that the same user with the same GPS looking for the same coordinates each day will end up with seven markers at quite different directions and distances from the pin.

Why is the nail even needed?

Because the test is to see if your GPS will take you to the same place each time, and if not then how far off will you be each time, and the nail/pin/known location/target whatever you want to call it is the only way to know how different the reading is each day.

 

And if you think it is pointless, please don't do it!

This isn't an accuracy test, as claimed. It's a consistency test.

 

consistency ≠ accuracy

 

And as mentioned, the whole "nail" thing is pointless. It's just one more reading, no better or worse than the others.

 

A better test for consistency is simply to pick out an identifiable spot, and take a reading there every 11 hours and 58 minutes. Let the GPS settle for exactly 5 minutes, and record the coordinates. Do that for a week, and see how close the coordinates are to each other.

Edited April 26, 2010 by Prime Suspect

[+AuntieWeasel]

Well, I've had three handhelds so far, and none of them ever gets to zero and stays there. I'm almost never "right on top" of the cache, per the navigation screen.

 

The best I can do is, "it's four feet W...it's 16 feet W...it's 5 feet N." I mean, where the marker is, per my device, depends on when you tell me to stop trying to find it.

 

Equally instructive is just to sit in a field holding the GPS and watch the breadcrumb trail spike all around you.

[+briansnat]

This isn't an accuracy test, as claimed. It's a consistency test. consistency ≠ accuracy And as mentioned, the whole "nail" thing is pointless. It's just one more reading, no better or worse than the others. A better test for consistency is simply to pick out an identifiable spot, and take a reading there every 11 hours and 58 minutes. Let the GPS settle for exactly 5 minutes, and record the coordinates. Do that for a week, and see how close the coordinates are to each other.

 

Exactly.

[+BulldogBlitz]

i don't have to do this test in my front yard...

 

apparently, there is a nearby cache which is akin to a nail in the ground... wide open field. i've been out 3 times looking for it. each time, the GPS takes me back to the same 10 foot circle... which appears to coincide with what google earth has marked as the location too...

 

still haven't found that thing though.

[+TheAlabamaRambler]

i don't have to do this test in my front yard...

 

apparently, there is a nearby cache which is akin to a nail in the ground... wide open field. i've been out 3 times looking for it. each time, the GPS takes me back to the same 10 foot circle... which appears to coincide with what google earth has marked as the location too...

 

still haven't found that thing though.

Yup, that's how I first discovered how much my GPS varied from day to day.

 

The cache Go Nuts was a film can set in a piece of pipe in the ground where the top of the film can was even with the surface of the ground and covered with camo tape that perfectly matched the grass around it.

 

At that time I was caching with a lot of different people and would often revisit caches I had found so my partners could look for them.

 

Over a couple of years I ended up visiting that cache a total of 15 times, replaced the log twice when it was wet and the container once when it went missing, and still DNF'd it EIGHT of those times! It was EVIL to find!

 

That experience educated me on how difficult it is to get a GPS to return to the same spot.

 

What prompted this thread and test is the number of people with whom I talk or read on these forums who are confused or frustrated with, or have unrealistic expectations about, the ability of a GPS to give them spot-on accuracy (or consistency, if that makes you happy).

[+Prime Suspect]

What prompted this thread and test is the number of people with whom I talk or read on these forums who are confused or frustrated with, or have unrealistic expectations about, the ability of a GPS to give them spot-on accuracy (or consistency, if that makes you happy).

It's not a matter of happiness. Accuracy and consistency are two different things. If you go to a carnival midway rifle range, you may find that any individual rifle may be very consistent, but it probably won't be accurate.

[+paleolith]

Interesting, I may do it. I expect a large spread due to nearly complete canopy coverage in my yard.

 

I agree that the nail is not necessary. I would picked a set of coordinates which I'm sure are in my yard, do the experiment on those coords, compute the centroid of my measurements and the average distance from the centroid -- or perhaps the mean squared distance, since the area to be searched increases as the square of the discrepancy.

 

Other variations:

 

Do it four or more times per day to determine how much the configuration of the birds matters.

 

On each measurement, first get to the zero point as fast as possible and mark it. Then average for five minutes and record the reading. How much tighter do the averaged readings cluster? (When the average differs from the quick reading, you'll have to calculate where to place your marker, since you don't want to do a lot of five-minute readings to locate your zero.)

 

The general goal of getting people to realize how far off their readings are likely to be has specific applicability to hiding. People who realize the potential error are more likely to take the five or ten minutes to get a good average.

 

Personally I have not observed discrepancies among brands of GPSr. If complaints about accuracy of coords is frequent on a cache, then either everyone is reporting the same error, or the reception is bad and it jumps all around. I don't recall a cache where accuracy complaints excluded any brand of GPSr.

 

I'd have saved myself some grief (and perhaps money) if I'd done this as soon as I bought my first GPSr. It took me several months to realize that is was sometimes giving me seriously bad readings, up to 100' off. At first I just rebooted it, which often reduced the error a lot. Only when it was long out of warranty did I start realizing that it was just a dud. One cache, I knew the basic location, GPSr told me to go 75' away and jump off a cliff. On another it kept bouncing me back and forth between two or three locations, and I knew they were all wrong (and scattered over 100' or more). Replacing reduced my DNF rate significantly. At first I thought it had "gone" bad, but later realized that I'd been having very bad readings from the start and just did not realize it. (I'm not naming it because I'm sure it was just a flawed sample, not a flawed design.)

 

The amazing thing is that I hid six caches using that GPSr (which did not even have an average function) and no one has had any trouble finding them due to bad coords. Of course it helps that they were all ammo cans and hardly hidden at all -- all were in locations that said "I DARE a muggle to come here".

 

Edward

[+dfx]

It's not a matter of happiness. Accuracy and consistency are two different things. If you go to a carnival midway rifle range, you may find that any individual rifle may be very consistent, but it probably won't be accurate.

but how can a GPS receiver be consistently inaccurate?

[+TheAlabamaRambler]

What prompted this thread and test is the number of people with whom I talk or read on these forums who are confused or frustrated with, or have unrealistic expectations about, the ability of a GPS to give them spot-on accuracy (or consistency, if that makes you happy).

It's not a matter of happiness. Accuracy and consistency are two different things. If you go to a carnival midway rifle range, you may find that any individual rifle may be very consistent, but it probably won't be accurate.

Acknowledging that I'm not smart enough to debate semantics, I will still give it a try...

 

Given a known point - the pin which represents for this purpose a geocache, a GPS will consistently take you to an inaccurate location (somewhere other than the pin).

 

Does that make you happy?

Edited April 27, 2010 by TheAlabamaRambler

[+Mosaic55]

 

I agree that the nail is not necessary. I would picked a set of coordinates which I'm sure are in my yard, do the experiment on those coords, compute the centroid of my measurements and the average distance from the centroid -- or perhaps the mean squared distance, since the area to be searched increases as the square of the discrepancy.

 

Ah, that seems like a good way to perform the exercise without an accomplice. Thanks.

[+TheAlabamaRambler]

 

I agree that the nail is not necessary. I would picked a set of coordinates which I'm sure are in my yard, do the experiment on those coords, compute the centroid of my measurements and the average distance from the centroid -- or perhaps the mean squared distance, since the area to be searched increases as the square of the discrepancy.

 

Ah, that seems like a good way to perform the exercise without an accomplice. Thanks.

What y'all are ignoring is that if you know where true GZ is, be it a pin or a set of coordinates that you recorded, then you will likely, consciously or not, try to affect the test. You are less likely to place a marker where the GPS tells you is GZ when you know that the real GZ is over there a ways.

[+fizzymagic]

What y'all are ignoring is that if you know where true GZ is, be it a pin or a set of coordinates that you recorded, then you will likely, consciously or not, try to affect the test. You are less likely to place a marker where the GPS tells you is GZ when you know that the real GZ is over there a ways.

TAR, I think your experiment is well thought-out and would be quite useful to give people a sense of how their GPS devices really work. And I am a Real Scientist, even. I am really amazed at the responses you have gotten. Apparently science is not taught very well in the schools any more.

 

At any rate, I think that your original experiment (with the nail) is quite good.

[cejs]

I tried this experiment with the Trimble R8 GPS that lives in our office. My co-workers came within a few inches 5 out of 5 times. I might have to go back and test my caches with this thing!

 

I'm going to bring my Delorme pn-40 in tomorrow and try with a different set of co-workers. I'm not expecting the same results, but am curious how far off it really is.

[Clan Riffster]

A better test for consistency is simply to pick out an identifiable spot, and take a reading there every 11 hours and 58 minutes. Let the GPS settle for exactly 5 minutes, and record the coordinates. Do that for a week, and see how close the coordinates are to each other.

I've done something similar. While I didn't find it particularly scientific, it did provide some food for thought:

There's a big root in my front yard, where there is a clear patch of sky overhead. On a (mostly) daily basis, I fired up my 60CSx, my Colorado 400i, my Oregon 300 and my work GPSr, a Vista HCx. I would walk to the root and take a set of coords for it. Because I wasn't all that interested in precise results, I would repeat this at varying times of day, for several days, whenever I remembered to do so. I plotted the resulting coords set, seeing which one created a tighter group. The groups were very close in size, and went from smallest to largest in the aforementioned order.

 

Based solely upon this entirely unscientific study, I tell folks my opinions regarding the "accuracy" of each device.

 

On a side note, this test also showed me that there was almost no difference between coords I just grabbed and coords I obtained through averaging.

[+TheAlabamaRambler]

We've done this at a number of events, it's always enlightening.

 

At one event in Arkansas we had geocachers who were professional surveyors bring their high-dollar rig the day before to set a steel rod in the ground so that it was very accurately located and completely hidden.

 

After everyone (about forty participants) had placed their flags the surveyors used a metal detector to locate and reveal the rod.

 

The closest flag was about four feet, the farthest over sixty.

 

That's about the spread we've seen every time we've done this at events.

[+thecaswellfamily]

 

Based solely upon this entirely unscientific study, I tell folks my opinions regarding the "accuracy" of each device.

 

 

Do tell, do tell! What are your opinions regarding the accuracy of those devices?

[Clan Riffster]

"Accuracy" isn't quite the right word, but it's all I got so, in order of most accurate to least accurate:

Garmin 60CSx, Garmin Colorado 400i, Garmin Oregon 300, Garmin Vista HCx.

The difference between the average spread on the 60 and the Vista was only about 9'.

Oddly enough, the 60 is the oldest one I own, and has taken the greatest abuse.

[oakenwood]

In place of the nail, you can use an adjusted benchmark, if it's convenient. You'll just have to pretend not to know where it is.

[+Huntleigh]

I'm thinking this is a neat idea for a cache.

 

Place a bag containing green golf tees, with a sign explaining the exercise, near the cache and ask people to take one. At the very moment they spot the cache, place the golf tee in the ground, like near the toes of their right foot, push it all the way down so it is flush with the ground. Remember to place the cache exactly as you found it.

 

Then CO goes out after a month or first 30 finds and makes a chart, put it on the page and either continue the experiment or remove the tees and sign.

 

Anything for a new cache gimmick, eh?

 

Could also be a fun game for an outdoor event.

 

Something like this cache? GC1CZ3B Accuracy

[+joespaz]

Write Shop Robert says, "This is the way to test your GPS accuracy." (but his computer is off right now so I'm typing it here)

 

http://www.geocaching.com/seek/cache_detai...b7-30c4583a1fa7

[+WRITE SHOP ROBERT]

Write Shop Robert says, "This is the way to test your GPS accuracy." (but his computer is off right now so I'm typing it here)

 

http://www.geocaching.com/seek/cache_detai...b7-30c4583a1fa7

Yep, that's what I said...Now I have the computer on...the method of measuring your GPS against others will not tell you anything about accuracy, nor will measuring it against itself. Even if you follow your GPS to same coordinates 100 times and get a 12 foot circle, you have no way to know if that circle is 20 feet away from the real coordinates. The way to measure accuracy is to compare the reading on your unit to a KNOWN ACCURATE location.

 

How far were you from X when your GPS said zero?

[+TheAlabamaRambler]

Fine business. I acknowledge that the word accuracy is misleading some people. If I could change the thread title I would.

 

This voluntary (meaning that you don't have to participate if you think it is flawed or not fun) exercise shall from this point forward be about the ability to navigate to a known point repeatedly... just for fun let's call it 'consistency'

 

The question is: How close to a given set of coordinates for a hidden object will your GPS get you and how closely will it take you back to that hidden object each day for one week.

 

The expected response is, for those cachers who choose to participate: Once the hidden object is revealed how far and in what direction were the seven markers you set from the revealed target.

 

I hope that clears up any confusion and allows this thread to get back on topic.

Edited April 28, 2010 by TheAlabamaRambler

[+GeoGeeBee]

What y'all are ignoring is that if you know where true GZ is, be it a pin or a set of coordinates that you recorded, then you will likely, consciously or not, try to affect the test. You are less likely to place a marker where the GPS tells you is GZ when you know that the real GZ is over there a ways.

TAR, I think your experiment is well thought-out and would be quite useful to give people a sense of how their GPS devices really work. And I am a Real Scientist, even. I am really amazed at the responses you have gotten. Apparently science is not taught very well in the schools any more.

 

At any rate, I think that your original experiment (with the nail) is quite good.

 

But the nail really doesn't add any useful data. It's just another reading, no better nor worse than the others. The only difference is that it is sort-of hidden, in an attempt to keep from influencing the other "finders" when they plant their flags.

 

The result, of course, is that the subsequent finders are affected by the first flag, rather than the nail.

 

A better model would be to make an accurate map of your yard on paper. After each find, use a tape measure to place the flag in relation to fixed landmarks, mark it on your map, and remove the flag. That way subsequent finders are not influenced by previous finders.

 

It's still a good exercise.

 

And if you don't want to go to all that work, do this much simpler version: Pick a landmark... a big rock, your mailbox, whatever. Get your best reading on your GPS, mark a waypoint. Go back an hour later, put your GPS on the same landmark, and note how far away it says the waypoint is.

 

Every new geocacher should be encouraged to do this at least once, before they post a "coordinates were off by 12 feet" log.

[+fizzymagic]

TAR, I think your experiment is well thought-out and would be quite useful to give people a sense of how their GPS devices really work. And I am a Real Scientist, even. I am really amazed at the responses you have gotten. Apparently science is not taught very well in the schools any more.

But the nail really doesn't add any useful data. It's just another reading, no better nor worse than the others. The only difference is that it is sort-of hidden, in an attempt to keep from influencing the other "finders" when they plant their flags.

Incorrect.

 

The nail allows the simulation of geocaching, where finders attempt to locate something hidden by a person who then took coordinates with a GPS. It needs to be actually, not "sort-of" hidden in order for the experiment to work properly.

 

The result, of course, is that the subsequent finders are affected by the first flag, rather than the nail.

Since the subsequent seekers have no way of knowing whether the first flag is correct or not, that would be useful in showing the magnitude of the prior knowledge problem. Because it does present a problem of "confirmation bias."

 

A better model would be to make an accurate map of your yard on paper. After each find, use a tape measure to place the flag in relation to fixed landmarks, mark it on your map, and remove the flag. That way subsequent finders are not influenced by previous finders.

Yes, that would be a good thing to do. It is a better simulation of geocaching.

[+Vater_Araignee]

I can show the problem of inconsistency.

I placed my unit on a parking post for 5 minutes.

then I deleted the track file and started waypoint averaging, once I was done saving the point I saved the track file, all without moving the unit.

The bulls eye = 250 samples, with a 30.81 foot deviation.

The blue line = the track file made wile averaging.

The white line with red ends is a ruler showing 107.59 feet.

The sharp angle above the m in samples is where the post is (if GE was as accurate as some wish it to be)

[+Scubasonic]

You guys do that I will go out and find some caches. Seems like a waste of time to me.

 

Scubasonic

[+TheAlabamaRambler]

You guys do that I will go out and find some caches. Seems like a waste of time to me.

 

Scubasonic

Buh-bye.

 

Wouldn't want to waste your time, since I see you're busy reading and posting such helpful stuff here.

 

When you get a minute between caches fix the spelling error in your sig line...

 

"This is just to fun !!!"

Edited April 28, 2010 by TheAlabamaRambler

[Andronicus]

Not sure the nail is necisary. Point one would act the same. I think that it would be a good exersise just to help you visualize the limitations of your GPSr. So far, I have been using benchmarks to do a similar test. I have been recording the accuracy at over 50 benchmarks. Sometimes it is way off (10m), but usualy 3m. Even 3m gives you a GZ of 6m (3m hider + 3m finder = 6m).

[+WRITE SHOP ROBERT]

You guys do that I will go out and find some caches. Seems like a waste of time to me.

 

Scubasonic

Not really, just another way to play with your GPS. Thare are lot's of ways to play with it besides just finding Caches. Have fun out there.

[+fizzymagic]

Even 3m gives you a GZ of 6m (3m hider + 3m finder = 6m).

Yet another misconception that doing the test could correct.

[+Prime Suspect]

Incorrect.

 

The nail allows the simulation of geocaching, where finders attempt to locate something hidden by a person who then took coordinates with a GPS. It needs to be actually, not "sort-of" hidden in order for the experiment to work properly.

But the experiment wasn't to simulate geocaching. It was to measure GPS accuracy. You're re-writing the objective to fit the process.

 

The nail was an attempt to do a double-blind test. But unless the nail is known to actually be at the target coordinates (which would require survey-grade equipment) it doesn't serve its purpose.

[+sbell111]

You guys do that I will go out and find some caches. Seems like a waste of time to me.

 

Scubasonic

Buh-bye.

 

Wouldn't want to waste your time, since I see you're busy reading and posting such helpful stuff here.

 

When you get a minute between caches fix the spelling error in your sig line...

 

"This is just to fun !!!"

You sure do get your panties wadded easily.

[+TheAlabamaRambler]

You guys do that I will go out and find some caches. Seems like a waste of time to me.

 

Scubasonic

Buh-bye.

 

Wouldn't want to waste your time, since I see you're busy reading and posting such helpful stuff here.

 

When you get a minute between caches fix the spelling error in your sig line...

 

"This is just to fun !!!"

You sure do get your panties wadded easily.

I appreciate your concern about my underwear. You've always taken a particular interest in me, it seems, but I did not realize it was quite that personal. I'm really not interested in sharing the state, color or design of my undergarments with you, but I'm flattered by your interest.