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Bing seems to work best?

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Not sure about the experiences of the rest of the community; Google Maps always seems to be about 30ft off with nav. coords (translated for Google). In comparison, Bing Maps is dead on, maybe off by 3 ft. every single time I've geocached so far. I did a cross-comparison with caches I've already found and it holds up, Bing is on the money with coords given from owner, and Google is way off. Anybody else experience this??

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From what I've read, Google is accurate to a T in some areas, and way off in others. I suspect Bing might be similar. It's just that in your area, Google is off. ;)

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Not sure about the experiences of the rest of the community; Google Maps always seems to be about 30ft off with nav. coords (translated for Google). In comparison, Bing Maps is dead on, maybe off by 3 ft. every single time I've geocached so far. I did a cross-comparison with caches I've already found and it holds up, Bing is on the money with coords given from owner, and Google is way off. Anybody else experience this??

 

I find that Google is often within a couple feet. OSM on the other hand is off by a good half block.

 

But I guess that's why you don't use the maps to place a cache. :ph34r:

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Maps are overlays. ALL overlays are capable of being incorrect (period).

 

What you see may be true in your area, but it will most certainly be "off" somewhere else. Come to expect that, regardless of what maps you use.

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[ Since I apparently have to say this, this is not a post as a moderator/volunteer of Groundspeak. Your mileage may vary. Some assembly required. yadda yadda. ]

Google employee here within Geo. Gitchee-Gumme's answer is the closest so far to "right". The definition of "correct" is fuzzier than you might first think.

 

If you really want to engage in conversations of orthorectification and survey data and such, but be prepared to talk science and reality instead of smack talk. Coordinates are somewhat ambiguous if you associate them with a precision (which few do). Flat pictures of a non flat object (surely we'll agree the planet isn't flat...) are subject to distortion.

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[ Since I apparently have to say this, this is not a post as a moderator/volunteer of Groundspeak. Your mileage may vary. Some assembly required. yadda yadda. ]

Google employee here within Geo. Gitchee-Gumme's answer is the closest so far to "right". The definition of "correct" is fuzzier than you might first think.

 

If you really want to engage in conversations of orthorectification and survey data and such, but be prepared to talk science and reality instead of smack talk. Coordinates are somewhat ambiguous if you associate them with a precision (which few do). Flat pictures of a non flat object (surely we'll agree the planet isn't flat...) are subject to distortion.

 

Lol, no harm done, I get it. My original intent was to show my surprise that Bing of all things works around where I am. Nothing against Google unless you want to personally take it that way.

 

Chance of distortion on overlays makes complete sense, as I'm sure I'll come across something that doesn't work right. Thanks for the discussion.

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Not sure about the experiences of the rest of the community; Google Maps always seems to be about 30ft off with nav. coords (translated for Google). In comparison, Bing Maps is dead on, maybe off by 3 ft. every single time I've geocached so far. I did a cross-comparison with caches I've already found and it holds up, Bing is on the money with coords given from owner, and Google is way off. Anybody else experience this??

 

I find that Google is often within a couple feet. OSM on the other hand is off by a good half block.

 

But I guess that's why you don't use the maps to place a cache. :ph34r:

 

If you are talking OSM, most of the time it'a good, some parts of the world need some editing and nothing stops you to change it yourself.

 

But caching has nothing to do with maps, you don't even need one, only with precision of the coordinates the hider gave to the cache. (waypoint averaging)

Edited by splashy

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Not sure about the experiences of the rest of the community; Google Maps always seems to be about 30ft off with nav. coords (translated for Google). In comparison, Bing Maps is dead on, maybe off by 3 ft. every single time I've geocached so far. I did a cross-comparison with caches I've already found and it holds up, Bing is on the money with coords given from owner, and Google is way off. Anybody else experience this??

 

I find that Google is often within a couple feet. OSM on the other hand is off by a good half block.

 

But I guess that's why you don't use the maps to place a cache. :ph34r:

 

If you are talking OSM, most of the time it'a good, some parts of the world need some editing and nothing stops you to change it yourself.

 

But caching has nothing to do with maps, you don't even need one, only with precision of the coordinates the hider gave to the cache. (waypoint averaging)

 

Well, for know I'm not really in the go to afford a real GPS. :P

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Doesn't matter, if you have the coordinates the gps inside your phone will bring you near to the cache, the precision depends of the hider not you gps. The last part you have to search anyway, also with expensive models dedicated Gps.

If you want maps, you put some OSM on the phone (it's free) and one of these free nice apps for geocaching that works also OFFLINE.

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Even geolocation of roads is still iffy in many places. That's the reason that the automotive PND manufacturers still use a 'road snap' feature that, even if the fix is good and coordinates on the unit are correct, snaps you to the nearest road if you appear to be off by a bit. If it weren't for that, there are quite a number of places where the car-on-map view would turn into an interesting off-road adventure on the screen.

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Doesn't matter, if you have the coordinates the gps inside your phone will bring you near to the cache, the precision depends of the hider not you gps. The last part you have to search anyway, also with expensive models dedicated Gps.

If you want maps, you put some OSM on the phone (it's free) and one of these free nice apps for geocaching that works also OFFLINE.

 

Being that I'm just starting to geocache, my phone GPS and Trimble has already been very "inaccurate", at least to noob standards. 50 feet off south of GZ in an urban setting with no clues gives a looooootttttt of ground to be covered. Frustrating and a motivation to use a service with more accuracy, aka online maps prior to trekking out. These are the things poor college students like me have to resort to, although I am interested in OSM. I went to the website, and it's a great idea, but I'm nooottttt sure I understand where to see the GPS tracing on the map, nor how to get them on my phone. Will Google later.

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I don't know how many caches you did and if they are all from different persons. Maybe you are just unlucky.

As I said before you don't need a map to geocache. Only the coordinates are relevant.

 

The geocacher who placed the cache could have been very inaccurate.

In urban and and all kind of other places you can have a bad reception, even if your display says 10 or 7 feet, remember this is made of a calculation with all kind of variables coming out of the 'sky', the electronics calculate on what they have, this has nothing to do with fixed and defined variables.

 

If the person who placed the geocache had a lesser reception or a lesser receiver and did not average the waypoint AND you have a bed reception because of the same reasons then 50 feet is more then possible and not abnormal

 

Even a dedicated gps receiver most of the times will not bring you to GZ especially not in (city) canyons.

In the end you always have to search yourself.

 

What smartphone do you have? Be aware learning how it all works together needs some learning and time to read ALOT.

Edited by splashy

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Cached in multiple states and have been analyzing a bit for years the aerial (not satellite when you zoom in) images. For nearly 10 years while practicing architecture and for some years as a geocacher.

 

Google maps are VERY accurate. I have pointed out that point a few times and I always hear otherwise. Now I haven't been to every spot in the country but I can say I have been all over the DC, Miami (and now Tampa) regions and have YET to find things more than a foot or two off. This includes work with civil engineering an survey drawings I used within the AutoCad and later the BIMS software. It was not uncommon to use aerial images for preliminary site planning. A few times a parking lot or building line had to be adjusted, but again, on the magnitude of two feet or so.

 

Sometimes there are elements of the aerial that do make it unqualified for accuracy verification. One such situation I recently encountered was downtown Tampa where a poor quality aerial was used and direct overhead view was not used, but a bird's eye isometric view (angled view for the home gamer). Another dis-qualifier is shadows. Again, urban environments tend to be the most common place this has occurred in my trials. Once zoomed in, even if directly above, if taken while shadows were long, it may put areas in shadow to the point not reference point can be determined properly. This also occurs with tree lines mountains and other elements.

 

One excellent way to measure accuracy is via Geodetic survey marks and using the "benchmark" part of the site. Done this a number of times over the years and again have noted excellent accuracy (and observed iPhones are generally more accurate than a Garmin 60CSX). And yes, I have tried to keep my experiments/observations as scientific as possible.

 

As a final note, I wish cachers would use the aerial image more often to confirm the cache location. When you aren't even on the correct side of a roadway, you definitely don't have the coordinates right.

Edited by TheWeatherWarrior

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Cached in multiple states and have been analyzing a bit for years the aerial (not satellite when you zoom in) images. For nearly 10 years while practicing architecture and for some years as a geocacher.

 

Google maps are VERY accurate. I have pointed out that point a few times and I always hear otherwise. Now I haven't been to every spot in the country but I can say I have been all over the DC, Miami (and now Tampa) regions and have YET to find things more than a foot or two off. This includes work with civil engineering an survey drawings I used within the AutoCad and later the BIMS software. It was not uncommon to use aerial images for preliminary site planning. A few times a parking lot or building line had to be adjusted, but again, on the magnitude of two feet or so.

 

Sometimes there are elements of the aerial that do make it unqualified for accuracy verification. One such situation I recently encountered was downtown Tampa where a poor quality aerial was used and direct overhead view was not used, but a bird's eye isometric view (angled view for the home gamer). Another dis-qualifier is shadows. Again, urban environments tend to be the most common place this has occurred in my trials. Once zoomed in, even if directly above, if taken while shadows were long, it may put areas in shadow to the point not reference point can be determined properly. This also occurs with tree lines mountains and other elements.

 

One excellent way to measure accuracy is via Geodetic survey marks and using the "benchmark" part of the site. Done this a number of times over the years and again have noted excellent accuracy (and observed iPhones are generally more accurate than a Garmin 60CSX). And yes, I have tried to keep my experiments/observations as scientific as possible.

 

As a final note, I wish cachers would use the aerial image more often to confirm the cache location. When you aren't even on the correct side of a roadway, you definitely don't have the coordinates right.

 

I'm sure sooner or later I will come across a reading 'on the wrong side of the road', and yea, aerial image would come in handy when making it in first place. If and when I put my first cache down, I'll be sure to utilize all the methods for testing accuracy.

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I don't know how many caches you did and if they are all from different persons. Maybe you are just unlucky.

As I said before you don't need a map to geocache. Only the coordinates are relevant.

 

The geocacher who placed the cache could have been very inaccurate.

In urban and and all kind of other places you can have a bad reception, even if your display says 10 or 7 feet, remember this is made of a calculation with all kind of variables coming out of the 'sky', the electronics calculate on what they have, this has nothing to do with fixed and defined variables.

 

If the person who placed the geocache had a lesser reception or a lesser receiver and did not average the waypoint AND you have a bed reception because of the same reasons then 50 feet is more then possible and not abnormal

 

Even a dedicated gps receiver most of the times will not bring you to GZ especially not in (city) canyons.

In the end you always have to search yourself.

 

What smartphone do you have? Be aware learning how it all works together needs some learning and time to read ALOT.

 

Nexus 4. There's a free GPS 'calibrator' or something on Google Play that tests strength of satellites, readings, etc (stuff I don't entirely understand obviously), and from just walking around outside, it seems to be consistently off by 30ft....or as the app put it, an accuracy of 30ft?

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...it seems to be consistently off by 30ft....or as the app put it, an accuracy of 30ft?

This comment got me to wondering....

Are actually seeing a "consistent" deviation of 30ft?

Or is it that you are noticing the screen telling you an accuracy of 30ft... such as below (20ft in this case)?

29244923-e456-4690-97ce-d13b120f712a.png

 

This is an Estimated Positional Error (EPE) calculation. It is a GPS calculation based upon a wide array of variables. It has no bearing on whether your mapping is "off" or not.

 

All GPSr units and devices (consumer-grade, especially) have this EPE possibility variation -- it is unrelated to the mapping overlay. That reading would be present whether you are using maps or not.

When all is said and done -- if you consistently have a 30ft EPE reading, you are doing pretty good. It could be better, but I have seen far worse and I was still lead to the geocache without much problem.

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What does the manual say regarding that which the EPE (shown above as 20 feet) represents?

 

Is it the probability that the estimated position is within the EPE?

 

For example: 50%, 95%, 1 std. dev., 2 std. dev., other?

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People tend to THINK the gps is on spot, often this is because of car satnav where the cursor is on the road.

The trick here is it looks in the software where is the road nearby and it puts the cursor there right on the road.

 

As GG wrote " It is a GPS calculation based upon a wide array of variables."

 

This means, if it is fed with distorted signals it gets distorted info and the end result will be wrong, but the result has a margin between these calculations and the Gps (app) will show an EpE ESTIMATED position error, where the keyword is estimated, because nobody knows for sure.

Edited by splashy

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.... where the keyword is estimated, because nobody knows for sure.

Actually, most do not know. OTOH, those that design the software/firmware can run those simulations called "Monte Carlo Analyses" and calculate the percentages versus circle diameter as a statistic do know. They just keep it to themselves.

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From the Garmin Glossary ( http://www8.garmin.com/aboutGPS/glossary.html ):

 

Estimated Position Error (EPE)

A measurement of horizontal position error in feet or meters based upon a variety of factors including DOP and satellite signal quality.

 

DOP

See Dilution Of Precision.

 

Dilution Of Precision (DOP)

A measure of the GPS receiver/satellite geometry. A low DOP value indicates better relative geometry and higher corresponding accuracy. The DOP indicators are GDOP (geometric DOP), PDOP (position DOP), HDOP (horizontal DOP), VDOP (vertical DOP), and tdOP (time clock offset).

 

------------

 

A communication, seemingly from Garmin International to Joe (Prof. Joe Mehaffy(?), Francis Marion University, Florence, S.C.) Date unknown -- (Give special note to the final paragraph [emphasis added])

WHAT IS EPE?

 

Quote follows from Garmin Engineering

 

Joe,

 

The EPE is an estimation based upon the information the receiver

can determine. SA consists of artificial clock errors and

artificial ephemeral errors. Both of these effects, as well as

atmospheric effects, can result in a positional area of uncer-

tainty, which can be measured and will add to the receivers EPE.

Bias errors cannot be measured and will typically not be detected

in the EPE calculation.

 

The 12XL will typically have a better EPE than other units due to

the 12 channel correlator and the use of all tracked satellites

in the positional computation.

 

EPE is an estimation, rather than a measurement, but all

measurable factors are used in the estimation algorithm. We

consider the details of our EPE and FOM calculations proprietary.

 

We calculate EPE our own way. URE and HDOP are definitely

significant factors in the calculation. We calculate an over-

determined solution, and fully understand the characteristics of

SA, and are able (in our opinion) to provide for a better

estimate of current position error than the simplistic calcula-

tions will indicate.

 

Many folks have and will demand to know our specific calcula-

tions, but we consider these to be proprietary and we do not

release the specific formulas. This is similar in our FOM

calculation, we use a lot of finesse in our software which other

manufacturers have not been able to duplicate. This is further

evidenced by Dr. Wilson's reports on our accuracy compared to

other receivers. If the tests were performed, I believe you would

see closer correlation between our EPE values and actual errors,

as compared to other manufacturers units.

 

Garmin International

----------------

 

Team CowboyPapa speaketh the truth. :)

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From the Garmin Glossary ( http://www8.garmin.com/aboutGPS/glossary.html ):

 

Estimated Position Error (EPE)

A measurement of horizontal position error in feet or meters based upon a variety of factors including DOP and satellite signal quality.

 

DOP

See Dilution Of Precision.

 

Dilution Of Precision (DOP)

A measure of the GPS receiver/satellite geometry. A low DOP value indicates better relative geometry and higher corresponding accuracy. The DOP indicators are GDOP (geometric DOP), PDOP (position DOP), HDOP (horizontal DOP), VDOP (vertical DOP), and tdOP (time clock offset).

 

------------

 

A communication, seemingly from Garmin International to Joe (Prof. Joe Mehaffy(?), Francis Marion University, Florence, S.C.) Date unknown -- (Give special note to the final paragraph [emphasis added])

WHAT IS EPE?

 

Quote follows from Garmin Engineering

 

Joe,

 

The EPE is an estimation based upon the information the receiver

can determine. SA consists of artificial clock errors and

artificial ephemeral errors. Both of these effects, as well as

atmospheric effects, can result in a positional area of uncer-

tainty, which can be measured and will add to the receivers EPE.

Bias errors cannot be measured and will typically not be detected

in the EPE calculation.

 

The 12XL will typically have a better EPE than other units due to

the 12 channel correlator and the use of all tracked satellites

in the positional computation.

 

EPE is an estimation, rather than a measurement, but all

measurable factors are used in the estimation algorithm. We

consider the details of our EPE and FOM calculations proprietary.

 

We calculate EPE our own way. URE and HDOP are definitely

significant factors in the calculation. We calculate an over-

determined solution, and fully understand the characteristics of

SA, and are able (in our opinion) to provide for a better

estimate of current position error than the simplistic calcula-

tions will indicate.

 

Many folks have and will demand to know our specific calcula-

tions, but we consider these to be proprietary and we do not

release the specific formulas. This is similar in our FOM

calculation, we use a lot of finesse in our software which other

manufacturers have not been able to duplicate. This is further

evidenced by Dr. Wilson's reports on our accuracy compared to

other receivers. If the tests were performed, I believe you would

see closer correlation between our EPE values and actual errors,

as compared to other manufacturers units.

 

Garmin International

----------------

 

......

 

Allow me to note that another of GG's posts, the one above, is again in accordance with the suggestion of our moderator:

 

.. Gitchee-Gumme's answer is the closest so far to "right". The definition of "correct" is fuzzier than you might first think.

 

If you really want to engage in conversations of orthorectification and survey data and such, but be prepared to talk science and reality instead of smack talk. .....

 

That it contains definitive information in a scientific context.

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.... where the keyword is estimated, because nobody knows for sure.

Actually, most do not know. OTOH, those that design the software/firmware can run those simulations called "Monte Carlo Analyses" and calculate the percentages versus circle diameter as a statistic do know. They just keep it to themselves.

To summarize the above comments, while the manufacturers all provide the EPE's of their GPSrs, they do not provide the quantitative significance of that characteristic. Specifically, does that EPE encircle 2σ,75%, or 1σ of the locations determined. Since the manufacturers do not reveal their estimates of EPE, those curious enough will have to make their own determinations.

 

Well, I am that curious; consequently, I have begun to gather my own quantitative data to determine that which the EPE of my DeLorme PN-60 encircles. I have collected about 1/2 of the data which I consider to be minimally significant and it does look, preliminarily, very interesting.

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The only advantage that I've found with Bing over Google is that Bing's aerial "birds eye" is much better (clearer) than Google aerial imagery. (Sorry, robertlipe, it's true! unsure.giftongue.gif)

 

Other than that Google has proven to be far superior! smile.gif

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I think one of the comparisons between Bing and Google aerial images is how the images are processed. Google's images are always much darker and lower in contrast in my area (where we get 300+ days of sun a year). Bing's are much brighter and higher contrast. That's one of the things that leads me to Bing as often as not. Now, if they would just provide an easy way to start the zoom level at something much closer in after entering the initial coordinates...

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No apologies needed. The planet is a big place and taking "the best" picture of it all at once and serving it up usefully is really hard. It's a reality that some places will be better than others. I just spot-checked the capital section of Nashville and the Bat Buiding. It looks like Bing provides high contrast for the buildings by destroying the saturation of the ground colors (see how the ground, but not the buildings, looks like it's been run through a sepia filter?) Google Maps overlays road network data, road shields, and POI data. In this shot, Bing does a better job of keeping the buildings perpendicular to the ground. I know why it's this way, but Nashville is the Athens of the South, not the Pisa of the south; our buildings really don't lean like that. :-) So gold star to them for that.

 

I have no axe to grind. Use whatever works best for you in the areas you care about. If you remember The Bad Old Days when your choices were crappy Tiger data or $5,000 monthly ESRI subscriptions with optinally purchased aerial data (none of which was nearly as good as either of those products) you won't miss them and you'll welcome the choices.

 

http://i.imgur.com/CDBH4Iy.jpg

http://i.imgur.com/LnOqomn.jpg

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Actually, that satellite imagery from Google in your pictures is far better that what we get around here. (And for the first set of pictures, I think I like to Google images better.)

Bing is normally at the detail level that those are at, while Google's is less clear. I suppose it's just the area that I live in.rolleyes.gif (Plattsburgh isn't exactly the largest city in New York)

 

Google

 

Bing

Edited by ADKer

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Agreed. For that city, at this time, Bing "wins" as the images there aren't obliques or even shot with particularly awesome cameras. Looking at the bottom of the page, it looks like it's licensed imagery.

 

All the players (well, at least some of them) are racing to serve up better data all the time. I don't think that there's a strong case that any one company is "winning" everywhere. It's awesome to have competition and choices.

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