Corrdinates from GPSr compared with Google Earth coordinates

[+ustune]

I determine the coordinates of a known point in the city with my Garmin 60Csx and try to find this point in Google Earth by using coordinates from Garmin.

Coordinates from GPRs generally do not match the coordinates given by Google Earth for the same point.

Is this normal? How can we explain this?

[+Panther&Pine]

I determine the coordinates of a known point in the city with my Garmin 60Csx and try to find this point in Google Earth by using coordinates from Garmin.

Coordinates from GPRs generally do not match the coordinates given by Google Earth for the same point.

Is this normal? How can we explain this?

Google Earth should not be used to place caches. In some places it is accurate but in many others it is wildly off.

Trust the GPS.

[+thedeadpirate]

Google Earth is consistently 300' off here.

[ashnikes]

so wait, youre saying trying to determine cache location from satellite view through a google map is a bad idea? I should trust my constantly jumping around gps compas, or radar to find the cache, whereas google maps tends to be very consistant,

[+Panther&Pine]

so wait, youre saying trying to determine cache location from satellite view through a google map is a bad idea? I should trust my constantly jumping around gps compas, or radar to find the cache, whereas google maps tends to be very consistant,

What do you use radar for? Only in the context of geocaching please, I know what radar is used for.

 

To the OP. Google Earth is okay for getting a general idea of where a cache is/might be but it is not considered appropriate for placing caches.

[ashnikes]

so wait, youre saying trying to determine cache location from satellite view through a google map is a bad idea? I should trust my constantly jumping around gps compas, or radar to find the cache, whereas google maps tends to be very consistant,

What do you use radar for? Only in the context of geocaching please, I know what radar is used for.

 

To the OP. Google Earth is okay for getting a general idea of where a cache is/might be but it is not considered appropriate for placing caches.

radar as in the geocaching android app, not like weather radar

[+narcissa]

Google Earth's accuracy varies wildly from one place to the next. Part of the problem is that Google Earth uses flat images, but the Earth is round. Another issue is that Google Earth images vary in resolution, so it's not always possible to line the satellite images up with landmarks. I don't have to drive very far to be in an area where Google Earth can't show me individual trees the way it can in the city.

 

Google Earth is a great tool for figuring out the general location of a cache, good access points, and even rough coordinates for placing one. When you're placing a cache, you should always take coordinates with a handheld GPS device at the cache location. If you've started caching with a smartphone of some sort, but you're serious enough about the game that you'd like to place caches, it's a good idea to invest in a handheld GPSr. Smartphones are okay for getting into the game, but they have many limitations.

[+edscott]

Google Earth is consistently 300' off here.

 

Recognize anything here? If your 300 ft is correct your cache is not anywhere in the photo.

 

[+niraD]

so wait, youre saying trying to determine cache location from satellite view through a google map is a bad idea?

Specifically, determining the coordinates of the cache with Google Maps violates the guidelines: "You as the owner of the cache must visit the site and obtain the coordinates with a GPS."

I should trust my constantly jumping around gps compas, or radar to find the cache, whereas google maps tends to be very consistant,

Consistent and accurate are different things. Google Maps will be very consistent (at least until the next time Google updates the data on their servers). And around here, the satellite photos of Google Maps are high resolution and are calibrated very accurately. I've used Google Maps to produce coordinates that were at least as accurate as I could have gotten from a GPSr.

 

But I've seen places where Google Maps has only a tenth of the resolution, or where the calibration is off by a few hundred feet.

[+edscott]

so wait, youre saying trying to determine cache location from satellite view through a google map is a bad idea?

Specifically, determining the coordinates of the cache with Google Maps violates the guidelines: "You as the owner of the cache must visit the site and obtain the coordinates with a GPS."

I should trust my constantly jumping around gps compas, or radar to find the cache, whereas google maps tends to be very consistant,

Consistent and accurate are different things. Google Maps will be very consistent (at least until the next time Google updates the data on their servers). And around here, the satellite photos of Google Maps are high resolution and are calibrated very accurately. I've used Google Maps to produce coordinates that were at least as accurate as I could have gotten from a GPSr.

 

But I've seen places where Google Maps has only a tenth of the resolution, or where the calibration is off by a few hundred feet.

 

So by your logic GPS coordinates should also be forbidden. GPS units can wander off by hundreds of feet from time to time under certain conditions or in certain locations, and in these instances are far less predictable than Google maps. The real difference is that most anyone can read a number off a GPS, but not everyone can read a satellite image with a high degree of accuracy. So in the end we agree but not for the same reasons.

[I!]

I'd be interested to see how closely GPSr typically matches Google Maps in various places.

 

Example, partially censored:

• Standing at Google Maps point: N 51 51.### W 002 04.###
  
• GPSr reported location: N 51 51.###-004 W 002 04.###-002
  
• GPSr reported accuracy: 131 feet
  

Any others want to play?

[+Panther&Pine]

I'd be interested to see how closely GPSr typically matches Google Maps in various places.

 

Example, partially censored:

• Standing at Google Maps point: N 51 51.### W 002 04.###
  
• GPSr reported location: N 51 51.###-004 W 002 04.###-002
  
• GPSr reported accuracy: 131 feet
  

Any others want to play?

Yes!

Will do when I get home. I don't have the GPS here. Although I wonder... *wanders off to check something*

 

440 feet off. That is an entire block away from my house coordiantes.

I'm not trusting my life to Google Earth.

Edited June 24, 2010 by MooseJawSpruce

[+dfx]

I should trust my constantly jumping around gps compas, or radar to find the cache...

ignoring your "compass" and "radar" reference: if you had a proper GPSr, your coord readings wouldn't be "constantly jumping around", they would be very stable.

[+BulldogBlitz]

i don't know that i'd trust google as the first line for marking the co-ordinates.

 

putting the co-ordinates for a known cache into google maps here gets fairly accurate - seems to be within 5 feet.

 

putting the co-ordinates into google earth seems to get a wild swing of 100+ feet. i know i've seen the map adjust itself on google earth and move a cache quite a bit depending on the zoom.

 

as for the possibility of the GPSr being wildly innaccurate... well that is why you should take multiple readings. take several different routes to the cache location and record the co-ordinates each time. i'd hazard a guess that if you did it 5 times that all 5 would NOT be off by the same 100 feet each time (if you do consider your GPSr "wild").

[+dfx]

GPSr reported accuracy: 131 feet

lol? what kinda GPSr is that? iphone?

[I!]

GPSr reported accuracy: 131 feet

lol? what kinda GPSr is that? iphone?

eTrex Legend, 2002 model, since you ask. Next time you upgrade to a new GPSr, feel free to donate the old one

 

Back to the plot ...

 

Come on, people, let's have some quantitative data, like this:

• Standing at Google Maps point: N 51 51.### W 002 04.###
  
• GPSr reported location: N 51 51.###-004 W 002 04.###-002
  
• GPSr reported accuracy: 131 feet
  

[+mchaos]

so wait, youre saying trying to determine cache location from satellite view through a google map is a bad idea? I should trust my constantly jumping around gps compas, or radar to find the cache, whereas google maps tends to be very consistant,

What do you use radar for? Only in the context of geocaching please, I know what radar is used for.

 

To the OP. Google Earth is okay for getting a general idea of where a cache is/might be but it is not considered appropriate for placing caches.

radar as in the geocaching android app, not like weather radar

 

Okay, first off a satellite is taking pictures from fixed points in the sky, as you move up or down the pictures the angle from the satellite changes, there for making the map some what inaccurate.

 

I have seen that app, and know some one who uses it. It has never shown more then 7ft close to the cache, even when right on top of it. With my Triton I can always get to 00 on the distance from cache, and in most cases, if the coordinates were taken from a reliable unit, then I can drop my gps and it will land on the cache. (little exaggeration but I mean it puts me right were it is. Dead on.) Several times it has brought me standing over the cache. There was a nano I found, bison tube in the woods. It was in a hole drilled into a fallen tree. I would have never found it except that my GPS brought me right to the spot, I nearly set the gps on 00 on top of where the nano was in the tree. saw a loose piece of bark, and moved it and there it was. Your not gonna do that with a droid.

 

IMO and quite a few others I am sure, smart phones are much less reliable to place caches.

 

I have seen decent consistency with Google maps and others, but its still not accurate enough to place a cache. Besides, the RULES say that you cannot use Google maps or variants to obtain coords for placing a cache, So its a moot point!

 

Besides. "Radar" is just an app that displays how close you are to the GZ. It has nothing to do with the GPS receiver hardware in the phone. Its just not that accurate.

 

Do a Google search for "Droid GPS accuracy" and you will turn up numerous articles stating that the droids GPS is "widely off". From what I have read, the best you can get with a droid is about 10ft accuracy. That dribble compared to the 3ft accuracy I get with my unit, and most other GPS units.

 

Droid sux on batteries. Is not as sensitive as GPS units, in a thick wooded area, good luck with it.

 

As far as taking an accurate waymark for a cache placement, You should always let your GPS "Settle" before you mark it. I let mine settle fore a few minutes before I mark the placement.

 

My gps coords never jump around, unless I am moving, but it should then LoL.

 

EDIT: So as for taking coords for a cache placement, On google earth, how are you sure you are putting the pointer right were your cache is?? You should be taking the coords from the precise placement. There is no way, even with the droids poor 10ft accuracy if you get that even, its still much better then google maps. In a lot of cases its 20 ft, its still more accurate then google maps because you can set the droid down on top of the placement, let it settle, then waymark it. Then if its even 20 ft off from the exact cache placement, not an unknown amount of feet away. You cannot possibly click on the exact place the cache is hidden on google maps. You are not supposed to just take a waymark of some where in the area of the cache. It should be the coords right were the cache is.

 

If you want to make it harder by making the coords off on purpose, then make it a mystery cache.

 

So even though your droid is not the greatest for taking coords for a placement, it would be a lot better then using Google maps. If you like geocaching so much, go buy a specific GPSr. Wally world is clearance out the Triton series I have seen it for as little as $100 for a T400. You can always hit up ebay. I once got an explorist 210 for $30 shipped.

 

Ustune: As for the original question, You are trying to sync up an image with physical coordinates. To get as close as it is, is really darn good!

Edited June 24, 2010 by mchaos

[+dfx]

• Standing at Google Maps point: N 51 51.### W 002 04.###
  
• GPSr reported location: N 51 51.###-004 W 002 04.###-002
  
• GPSr reported accuracy: 131 feet
  

right. so .004 minutes in the latitude and .002 minutes in the longitude at this latitude makes a difference of roughly 7.8 meters, that's 25.6 feet. not a whole lot, but a modern GPSr can do better.

 

as for my own caches, the only cache where i can even try to use google is my one and only LPC (which is a puzzle cache). the difference is .002 minutes in the latitude and .001 in the longitude, which is 4 meters difference. quite good actually, but i wouldn't know that without having used a GPSr. as for my other caches, they're nowhere near any recognizeable objects, so can't use google at all for those.

Edited June 24, 2010 by dfx

[+ustune]

so wait, youre saying trying to determine cache location from satellite view through a google map is a bad idea? I should trust my constantly jumping around gps compas, or radar to find the cache, whereas google maps tends to be very consistant,

What do you use radar for? Only in the context of geocaching please, I know what radar is used for.

 

To the OP. Google Earth is okay for getting a general idea of where a cache is/might be but it is not considered appropriate for placing caches.

radar as in the geocaching android app, not like weather radar

 

Okay, first off a satellite is taking pictures from fixed points in the sky, as you move up or down the pictures the angle from the satellite changes, there for making the map some what inaccurate.

 

I have seen that app, and know some one who uses it. It has never shown more then 7ft close to the cache, even when right on top of it. With my Triton I can always get to 00 on the distance from cache, and in most cases, if the coordinates were taken from a reliable unit, then I can drop my gps and it will land on the cache. (little exaggeration but I mean it puts me right were it is. Dead on.) Several times it has brought me standing over the cache. There was a nano I found, bison tube in the woods. It was in a hole drilled into a fallen tree. I would have never found it except that my GPS brought me right to the spot, I nearly set the gps on 00 on top of where the nano was in the tree. saw a loose piece of bark, and moved it and there it was. Your not gonna do that with a droid.

 

IMO and quite a few others I am sure, smart phones are much less reliable to place caches.

 

I have seen decent consistency with Google maps and others, but its still not accurate enough to place a cache. Besides, the RULES say that you cannot use Google maps or variants to obtain coords for placing a cache, So its a moot point!

 

Besides. "Radar" is just an app that displays how close you are to the GZ. It has nothing to do with the GPS receiver hardware in the phone. Its just not that accurate.

 

Do a Google search for "Droid GPS accuracy" and you will turn up numerous articles stating that the droids GPS is "widely off". From what I have read, the best you can get with a droid is about 10ft accuracy. That dribble compared to the 3ft accuracy I get with my unit, and most other GPS units.

 

Droid sux on batteries. Is not as sensitive as GPS units, in a thick wooded area, good luck with it.

 

As far as taking an accurate waymark for a cache placement, You should always let your GPS "Settle" before you mark it. I let mine settle fore a few minutes before I mark the placement.

 

My gps coords never jump around, unless I am moving, but it should then LoL.

 

EDIT: So as for taking coords for a cache placement, On google earth, how are you sure you are putting the pointer right were your cache is?? You should be taking the coords from the precise placement. There is no way, even with the droids poor 10ft accuracy if you get that even, its still much better then google maps. In a lot of cases its 20 ft, its still more accurate then google maps because you can set the droid down on top of the placement, let it settle, then waymark it. Then if its even 20 ft off from the exact cache placement, not an unknown amount of feet away. You cannot possibly click on the exact place the cache is hidden on google maps. You are not supposed to just take a waymark of some where in the area of the cache. It should be the coords right were the cache is.

 

If you want to make it harder by making the coords off on purpose, then make it a mystery cache.

 

So even though your droid is not the greatest for taking coords for a placement, it would be a lot better then using Google maps. If you like geocaching so much, go buy a specific GPSr. Wally world is clearance out the Triton series I have seen it for as little as $100 for a T400. You can always hit up ebay. I once got an explorist 210 for $30 shipped.

 

Ustune: As for the original question, You are trying to sync up an image with physical coordinates. To get as close as it is, is really darn good!

 

Thanks for explanations.

Just to avoid any off-topic replies, let me clarify my point : My intention is not to place a cache based on Google Earth data. I use a GPSr proper for cache placing and reporting purposes. However, when I look at the coordinates obtained by GPSr on Google Earth, Google Earth shows a way-off point. As an example, coordinates of a well known place, such as a bridge, taken by a GPSr shows a point far off from the bridge in Google Earth.

If this is normal, then anybody using the coordinates of the GPSr in Google Earth would be misled. In other words, say that coordinates from the beginning of a long bridge would point to the end of the bridge in Google Earth.

My question is : Is this accepted as "normal"? According to your explanations, answer is "yes" !

[+dfx]

However, when I look at the coordinates obtained by GPSr on Google Earth, Google Earth shows a way-off point. As an example, coordinates of a well known place, such as a bridge, taken by a GPSr shows a point far off from the bridge in Google Earth.

If this is normal, then anybody using the coordinates of the GPSr in Google Earth would be misled. In other words, say that coordinates from the beginning of a long bridge would point to the end of the bridge in Google Earth.

My question is : Is this accepted as "normal"? According to your explanations, answer is "yes" !

yes it is. that's exactly why you're not supposed to use google for obtaining coords for a cache placement, even though some people here don't wanna believe that.

 

of course there's also other factors that may give you the same result, such as a different coordinate datum on the GPSr, or using a wrong coordinate format.

Edited June 24, 2010 by dfx

[I!]

as for my own caches, the only cache where i can even try to use google is my one and only LPC (which is a puzzle cache). the difference is .002 minutes in the latitude and .001 in the longitude

Cool. So that's two data points now:

• Standing at Google Maps point: N 51 51.### W 002 04.###
  
• GPSr reported location: N 51 51.###-004 W 002 04.###-002
  
• GPSr reported accuracy: 131 feet
  

• Standing at Google Maps point: N 43 ##.### W 080 ##.###
  
• GPSr reported location: N 43 ##.###±002 W 080 ##.###±001
  
• GPSr reported accuracy: ?
  

Any more? How about the original poster?

[+chasclifton]

However, when I look at the coordinates obtained by GPSr on Google Earth, Google Earth shows a way-off point. As an example, coordinates of a well known place, such as a bridge, taken by a GPSr shows a point far off from the bridge in Google Earth.

If this is normal, then anybody using the coordinates of the GPSr in Google Earth would be misled. In other words, say that coordinates from the beginning of a long bridge would point to the end of the bridge in Google Earth.

My question is : Is this accepted as "normal"? According to your explanations, answer is "yes" !

yes it is. that's exactly why you're not supposed to use google for obtaining coords for a cache placement, even though some people here don't wanna believe that.

 

of course there's also other factors that may give you the same result, such as a different coordinate datum on the GPSr, or using a wrong coordinate format.

 

I placed two caches in a mountainous area recently, placing my GPSr on a rock and letting it settle down before taking a final reading on the coordinates.

 

Then, just for grins, I went home and entered those coordinates into Google Earth. In each case, it was "close but no cigar." For example, when the cache was at the edge of a small meadow, Google Earth put GZ out in the middle of the meadow.

 

I have, however, had better luck using Google Earth to find the approximate location of a cache before I go searching for it, which I think is the best use for that software.

[+GeoGeeBee]

as for my own caches, the only cache where i can even try to use google is my one and only LPC (which is a puzzle cache). the difference is .002 minutes in the latitude and .001 in the longitude

Cool. So that's two data points now:

• Standing at Google Maps point: N 51 51.### W 002 04.###
  
• GPSr reported location: N 51 51.###-004 W 002 04.###-002
  
• GPSr reported accuracy: 131 feet
  

• Standing at Google Maps point: N 43 ##.### W 080 ##.###
  
• GPSr reported location: N 43 ##.###±002 W 080 ##.###±001
  
• GPSr reported accuracy: ?
  

Any more? How about the original poster?

 

This is a waste of time. Your GPS is not going to give the same reading every time you go back to that spot. (At least, mine doesn't.)

[+mchaos]

as for my own caches, the only cache where i can even try to use google is my one and only LPC (which is a puzzle cache). the difference is .002 minutes in the latitude and .001 in the longitude

Cool. So that's two data points now:

• Standing at Google Maps point: N 51 51.### W 002 04.###
  
• GPSr reported location: N 51 51.###-004 W 002 04.###-002
  
• GPSr reported accuracy: 131 feet
  

• Standing at Google Maps point: N 43 ##.### W 080 ##.###
  
• GPSr reported location: N 43 ##.###±002 W 080 ##.###±001
  
• GPSr reported accuracy: ?
  

Any more? How about the original poster?

 

This is a waste of time. Your GPS is not going to give the same reading every time you go back to that spot. (At least, mine doesn't.)

 

That's mot what its about. They are taking a point on google maps, then checking it against a GPS to see the accuracy of Google maps.

 

Generally speaking google maps can be anywere from 50 to 300 ft off. They are trying to get instances from all over to see accuracy other places.

 

And, My GPS gets dadgum close....

[I!]

This is a waste of time. Your GPS is not going to give the same reading every time you go back to that spot. (At least, mine doesn't.)

No, GeoGeeBee, it's not a waste of time. If Google Maps calibration is as bad in places as is claimed then it would be instructive to see evidence of that in data of the proposed form. Then, at a glance, we can say that Google Maps is horribly-calibrated in locations X,Y,Z and pretty well calibrated at A,B,C. We might even be able to draw some evidence-based conclusions about accuracy vs. latitude, say. I think that would be interesting; and few-feet natural variation in GPSr readouts would not significantly detract from that.

 

EDIT: mchaos, thank you, that's what I'm getting at.

Edited June 24, 2010 by I!

[+edscott]

.....

 

That's mot what its about. They are taking a point on google maps, then checking it against a GPS to see the accuracy of Google maps.

 

Generally speaking google maps can be anywere from 50 to 300 ft off. They are trying to get instances from all over to see accuracy other places.

 

And, My GPS gets dadgum close....

 

How about this test. Your We will ROCK YOU! cache is 55.6 meters SW of the western edge of the power line clearing along the trail in the narrow strip between the trail and the water. I've never had problems in NJ, but of course winter photos are much easier to read.

[+ustune]

as for my own caches, the only cache where i can even try to use google is my one and only LPC (which is a puzzle cache). the difference is .002 minutes in the latitude and .001 in the longitude

Cool. So that's two data points now:

• Standing at Google Maps point: N 51 51.### W 002 04.###
  
• GPSr reported location: N 51 51.###-004 W 002 04.###-002
  
• GPSr reported accuracy: 131 feet
  

• Standing at Google Maps point: N 43 ##.### W 080 ##.###
  
• GPSr reported location: N 43 ##.###±002 W 080 ##.###±001
  
• GPSr reported accuracy: ?
  

Any more? How about the original poster?

Original poster reports

• Standing at Google Maps point: N 41 01.### E 028 57.###
  
• GPSr reported location: N 41 01###+015 E 028 57.###+011
  
• GPSr reported accuracy: 20 ft
  
• GPRs : Garmin GPSmap 60CSx
  

[+mchaos]

Here is my contribution...

• Starting at Google maps point: N40° 59.###" W-74° 57.###"
  
• GPSr reported location: N 40° 58.### W -74° 57###
  
• GPSr reported accuracy: 174ft
  

Edited June 24, 2010 by mchaos

[+roziecakes]

so wait, youre saying trying to determine cache location from satellite view through a google map is a bad idea? I should trust my constantly jumping around gps compas, or radar to find the cache, whereas google maps tends to be very consistant,

 

It depends on where you live. In some places, Google Maps/Earth may be right on accurate, but in many places it isn't. As for a jumping around GPSr, taking good coords for a cache can sometimes take a while, especially if you're placing the cache out in the sticks under tree cover, in a very urban setting where there's the urban canyon effect, etc.

 

You can't just grab coords and let it be; usually it takes several readings to get a good one for a cache hide. I've also heard from fellow geocachers that it's difficult to get good readings from smartphones for their hides, so they rely on their GPSr for coords when they hide caches.

 

A lot of my hides are way out in the boonies, so when I take coords I use both our GPSr's to take readings and try several times, and wait until the GPSr settles down enough; 'finding its bearings' my husband says. Even then it can be difficult.

 

If you find it impossible to get good coords, don't be afraid to say so on your page. I'll mention it. I'll be honest and say that I had a hard time getting coords if I do; and then I leave a better hint.

 

But generally, in conclusion, yes, it's better to use your GPSr even with a smartphone than using Google Maps/Earth.

[+dfx]

• Standing at Google Maps point: N 41 01.### E 028 57.###
  
• GPSr reported location: N 41 01###+015 E 028 57.###+011
  
• GPSr reported accuracy: 20 ft
  
• GPRs : Garmin GPSmap 60CSx
  

that's 32 meters off, aka 105 feet. that is pretty bad. but, as people have explained here, nothing unexpected.

 

If Google Maps calibration is as bad in places as is claimed then it would be instructive to see evidence of that in data of the proposed form. Then, at a glance, we can say that Google Maps is horribly-calibrated in locations X,Y,Z and pretty well calibrated at A,B,C. We might even be able to draw some evidence-based conclusions about accuracy vs. latitude, say.

that's not how it works. take a look at any LPC. you'll see the lamp post at an angle in the aerial view, meaning that if you'd pinpoint the base of the lamp post on google, and then pinpoint the top of the lamp post, you'd get different coords, off by several meters, whereas in reality the lamp post is clearly perfectly vertical and the coords should be the same. does that tell you anything?

Edited June 24, 2010 by dfx

[I!]

@dfx - let's stick with satellite view, thus getting round the aerial view problem (which in any case is minor, like GPSr variation, compared to the large-scale calibration errors that I'm asking people to demonstrate).

 

@ustune - thanks for the data!

 

@mchaos - how far different were your Google Maps and GPSr coordinates?

[+dfx]

@dfx - let's stick with satellite view, thus getting round the aerial view problem (which in any case is minor, like GPSr variation, compared to the large-scale calibration errors that I'm asking people to demonstrate).

satellite view and aerial view are interchangeable in this context. i'm saying aerial view because all the high-res pictures you see on google maps and earth aren't from satellites. in any case, whatever source the pictures come from, they always have the same problems, and they aren't minor.

Edited June 24, 2010 by dfx

[+trailhound1]

•Standing at Google Maps point: N ## 01' 01.58" W ### 41' 22.84"

•GPSr reported location: N ## 01' 01.53 W ### 41' 22.82"

•GPSr reported accuracy: 17 feet

 

Distance Apart 5.3 ft

 

 

•Standing at Google Maps point: N ## 01' 03.07" W ### 41' 24.58"

•GPSr reported location: N ## 01' 02.89 W ### 41' 24.43"

•GPSr reported accuracy: 17 feet

 

Distance Apart 21.9 ft

 

 

From these two locations Google Earth and my PN-20 are not very different. Even though I have seen Google Earth not show cache locations accurately before.

[+edscott]

• Standing at Google Maps point: N 41 01.### E 028 57.###
  
• GPSr reported location: N 41 01###+015 E 028 57.###+011
  
• GPSr reported accuracy: 20 ft
  
• GPRs : Garmin GPSmap 60CSx
  

that's 32 meters off, aka 105 feet. that is pretty bad. but, as people have explained here, nothing unexpected.

 

If Google Maps calibration is as bad in places as is claimed then it would be instructive to see evidence of that in data of the proposed form. Then, at a glance, we can say that Google Maps is horribly-calibrated in locations X,Y,Z and pretty well calibrated at A,B,C. We might even be able to draw some evidence-based conclusions about accuracy vs. latitude, say.

that's not how it works. take a look at any LPC. you'll see the lamp post at an angle in the aerial view, meaning that if you'd pinpoint the base of the lamp post on google, and then pinpoint the top of the lamp post, you'd get different coords, off by several meters, whereas in reality the lamp post is clearly perfectly vertical and the coords should be the same. does that tell you anything?

 

Yes it tells me you are reading the shadow of the lamp post not the post itself. If you know which hemisphere you are in then you'll be able to tell which end of the shadow is the base of the post.

 

PS: Reading shadows is sometimes easier than seeing the object itself. In a winter photo of a deciduous woods most all the shadows of the trees will be parallel, but there will be a select few that are heading in another direction. Those few aren't shadows of standing trees but downed trees and their length and direction will be relatively unique. Makes woodland navigation in those conditions relatively easy.

Edited June 24, 2010 by edscott

[+dfx]

Yes it tells me you are reading the shadow of the lamp post not the post itself. If you know which hemisphere you are in then you'll be able to tell which end of the shadow is the base of the post.

um, no. it's not only the lamp posts you see sideways, it's everything, especially noticeable with all the buildings. you don't only see the roofs from above, you also see the sides of the buildings. and it's not the same sides for all buildings, in fact you can tell where the aerial images are stitched together from observing the direction the buildings are "leaning".

[+edscott]

Yes it tells me you are reading the shadow of the lamp post not the post itself. If you know which hemisphere you are in then you'll be able to tell which end of the shadow is the base of the post.

um, no. it's not only the lamp posts you see sideways, it's everything, especially noticeable with all the buildings. you don't only see the roofs from above, you also see the sides of the buildings. and it's not the same sides for all buildings, in fact you can tell where the aerial images are stitched together from observing the direction the buildings are "leaning".

 

I've never seen this on regular Google aerial images.. If you are on Google Earth and zooming in at weird angles then yes the view will be distorted. On the other hand I just checked your newest hide and the map of that area is essentially unusable for anything. If that is standard for your neighborhood then I agree that GPS is your only option.

 

Here is what I'm used to using

Edited June 25, 2010 by edscott

[Moun10Bike]

um, no. it's not only the lamp posts you see sideways, it's everything, especially noticeable with all the buildings. you don't only see the roofs from above, you also see the sides of the buildings. and it's not the same sides for all buildings, in fact you can tell where the aerial images are stitched together from observing the direction the buildings are "leaning".

 

I've never seen this on regular Google aerial images.

 

Really?

 

[+StarBrand]

Almost any map is off a bit. It varies widely. Most published maps have a stated accuracy of around 48 feet at well known locations. My GPS consistently does better than that.

 

In a nearby town, Google Earth is near spot on in the center of town with features and GPS coordinates and many caches. Just 15 miles East the images are a good 150 feet off as are then given coordinates. Useless for caching. See: http://www.geocaching.com/map/default.aspx...;lng=-103.79042

 

North of here, about everything is 25 foot off and just another 5 miles away - everything is a good 250 foot off.

 

Too inconsistent for me to believe in it with any certainty.

[+edscott]

um, no. it's not only the lamp posts you see sideways, it's everything, especially noticeable with all the buildings. you don't only see the roofs from above, you also see the sides of the buildings. and it's not the same sides for all buildings, in fact you can tell where the aerial images are stitched together from observing the direction the buildings are "leaning".

 

I've never seen this on regular Google aerial images.

 

Really?

 

 

No I've never had distortions like this where I've cached. This is a typical city view.

 

[+edscott]

Duplicate post

Edited June 25, 2010 by edscott

[+dfx]

No I've never had distortions like this where I've cached.

it's not distortions, it's photography! every photograph has a certain amount of perspective in it. the closer the camera is to the object, the higher the amount of perspective, and the more the buildings will appear to be "leaning". on the other hand, the further away the camera is, the less detail you will get on the pictures.

[I!]

•Standing at Google Maps point: N ## 01' 01.58" W ### 41' 22.84"

....

•Standing at Google Maps point: N ## 01' 03.07" W ### 41' 24.58"

...

From these two locations Google Earth and my PN-20 are not very different. Even though I have seen Google Earth not show cache locations accurately before.

Thanks! I'll add these data to a single table later - but no time now as I'm late for work.

(btw, I'll assume these are in the vicinity of N 37° W 088°)

[I!]

In a nearby town, Google Earth is near spot on in the center of town with features and GPS coordinates and many caches. Just 15 miles East the images are a good 150 feet off as are then given coordinates. Useless for caching. See: http://www.geocaching.com/map/default.aspx...;lng=-103.79042

 

North of here, about everything is 25 foot off and just another 5 miles away - everything is a good 250 foot off.

This is really interesting. Your map, switched to satellite view, is most illuminating: it shows that the images have been stitched together. I wonder if you notice much variation in Google Maps' accuracy either side of those 'stitches'?

[I!]

Here are the scores on the doors so far:

							   +--------------------------------+
+------------------------------+   GPS receiver reported ...	+----------------+
| Google maps location		 | location			| accuracy | contributor	|
+------------------------------+---------------------+----------+----------------+
| N 29° 43.###' W 095° 46.###' | N +0.001' W +0.000' |  13 feet | Hoosier Ranger |
| N 30° 54.###' W 084° 34.###' | (~30 feet North)	| ?		| GeoBain		|
| N 37° 01.###' W 088° 41.###' | N -0.001' W +0.000' |  17 feet | trailhound1	|
| N 37° 01.###' W 088° 41.###' | N -0.003' W -0.003' |  17 feet | trailhound1	|
| N 37° 24.###' W 122° 05.###' | N +0.002' W +0.000' | ?		| niraD		  |
| N 41° 38.###' W 088° 14.###' | (5.25 feet away)	| ?		| Markwell	   |
| N 40° 59.###' W 074° 57.###' | ?				   | 174 feet | mchaos		 |
| N 41° 01.###' E 028° 57.###' | N +0.015' E +0.011' |  20 feet | ustune		 |
| N 41° 49.###' W 103° 47.###' | variable (way off)  | ?		| StarBrand	  |
| N 43° ##.###' W 080° ##.###' | N ±0.002' W ±0.001' | ?		| dfx			|
| N 51° 51.###' W 002° 04.###' | N -0.004' W -0.002' | 131 feet | I!			 |
| N 51° 51.###' W 002° 04.###' | N +0.001' W +0.002' |  24 feet | I!			 |
+------------------------------+---------------------+----------+----------------+

To clarify: in this table, "GPS receiver location N -0.001' W +0.002'" would mean that the GPSr reported a location 0.001 South and 0.002 West of that claimed by Google Maps.

 

So, yep, there are some places where G-maps are pretty well calibrated and others where it's baaad.

Edited June 26, 2010 by I!

[+Hoosier Ranger]

Standing at Google Maps Point: N29 43. --- W095 46. ---

GPS Reported Location: N29 43.+001 W095 46. +/-000

13.2 feet of accuracy

100 averaged locations

Clear sky, no obstructions, 2 p.m. CDST

11 satellites received

Garman 60CSx

Location in Katy, TX

 

(I ALWAYS check Google Maps after placing a cache and averaging coordinates. If there is more than a few feet of discrepancy I go back and take more readings with the GPSr. Fortunately, there has never been very much variation.)

Edited June 25, 2010 by Hoosier Ranger

[+Coldgears]

I should trust my constantly jumping around gps compas, or radar to find the cache...

ignoring your "compass" and "radar" reference: if you had a proper GPSr, your coord readings wouldn't be "constantly jumping around", they would be very stable.

Or at least an android... Iphones suck, 100 feet off and don't even work when you have no connection. The android actually has a proper GPS in it, allowing it to work without coverage, AND is accurate to about 10 feet. Although, from my experience regular GPS do work somewhat better, not by a large margin.

[I!]

13.2 feet of accuracy

100 averaged locations

11 satellites received

Hoosier Ranger, I want your GPSr !!!

 

Many thanks for the data. Table updated.

[+niraD]

Okay, I'll play. Comparing coordinates from the satellite photos from Google Maps and from my handheld GPSr at N 37° 24.xxx W 122° 05.xxx, my GPSr coordinates differ by +0.002 N +0.000 W (about 12' north of the Google Maps coordinates).

[+Markwell]

GPS Coordinates (known from GPS and 9 years of using various units) and Google Earth coordinates are only 5.25 feet off at my house.

 

Would I use GE to hide a cache? No. I have used it to seek though.

 

Besides, the guidelines specifically state:

Guidelines that Apply to all Cache Types

(snip)

You as the owner of the cache must visit the site and obtain the coordinates with a GPS. GPS usage is an essential element of geocaching. Therefore, although it is possible to find a cache without a GPS, the option of using accurate GPS coordinates as an integral part of the cache hunt must be demonstrated for all physical cache submissions.

[viper1986]

Haha i dislike people dissing smartphones.

I think they MAY be a bit worse. But now with 66finds my blackberry gets me within grabbing distance almost every time.

Of course not EVERY time, but 90%

 

The only time when this is not true is under tree cover or major clouds...

And a few when the cache was moved....