Jump to content


Photo

How Accurate is Google Earth?


  • Please log in to reply
6 replies to this topic

#1 Thot

Thot

    Funtime Advisor

  • Senior Members
  • PipPipPip
  • 2,546 posts

Posted 24 August 2014 - 11:29 AM

Has anybody checked to see how accurate coordinates taken from Google Earth are?  I keep intending to do this but forget when I'm out.  They have to align the pictures to the Earth and I assume there's is varying amounts of error in that.  One way to do it would be to use an adjusted (accurate) benchmark that's easy to locate accurately with respect to landmarks that can be easily seen from the sky view and see how close Google coordinates match the real coordinates.  It would probably be necessary to do this for 4-5 benchmarks to get a good feel for the error. 



#2 TheNorman

TheNorman

    Senior Member

  • Senior Members
  • PipPipPip
  • 585 posts
  • LocationHuntsville, Texas

Posted 24 August 2014 - 11:56 AM

Here's a reference on the subject:  http://www.ijmse.org...sue6/paper2.pdf  In that paper they indicate that the RMS error in horizontal coordinates is 1.59 m and the RMS error in height is 1.7 m.

 

The paper is about Khartoum.  I don't know if their errors will be the same to other regions such as Houston, but it is a start.



#3 ATMA

ATMA

    Slightly Confused

  • Senior Members
  • PipPipPip
  • 3,404 posts
  • LocationNASA JSC Area

Posted 24 August 2014 - 02:20 PM

Here's a reference on the subject:  http://www.ijmse.org...sue6/paper2.pdf  In that paper they indicate that the RMS error in horizontal coordinates is 1.59 m and the RMS error in height is 1.7 m.

 

The paper is about Khartoum.  I don't know if their errors will be the same to other regions such as Houston, but it is a start.

Not bad RMS Error.



#4 Thot

Thot

    Funtime Advisor

  • Senior Members
  • PipPipPip
  • 2,546 posts

Posted 24 August 2014 - 03:04 PM

Here's a reference on the subject:  http://www.ijmse.org...sue6/paper2.pdf  In that paper they indicate that the RMS error in horizontal coordinates is 1.59 m and the RMS error in height is 1.7 m.

 

The paper is about Khartoum.  I don't know if their errors will be the same to other regions such as Houston, but it is a start.

Excellent article!  Thanks.



#5 HoustonControl

HoustonControl

    Charter Member

  • Senior Members
  • PipPipPip
  • 9,864 posts
  • LocationBaytown

Posted 24 August 2014 - 03:17 PM

I've found them to be very good, as far as I can tell, and usually use GE to verify and fine tune my coordinates when hiding caches..  I found a cache recently that was 50' off from where my GPSr was pointing.  When I checked the coordinates in Google Earth, they indicated the exact spot my GPSr was taking me. 

 

Also, I figure the GE results will be the same as indicated on the Geocache App map view, and a lot of folks use the app.  If the cache is hidden in the second tree past the last light pole on the SE corner of the parking lot, I'd like the icon to appear there on the map view of the app.


img.aspx?txt=What+in+the+Hell?&uid=1dd8c

#6 heftydude

heftydude

    Senior Member

  • Senior Members
  • PipPipPip
  • 705 posts
  • LocationHouston

Posted 26 August 2014 - 07:34 PM

I've found them to be very good, as far as I can tell, and usually use GE to verify and fine tune my coordinates when hiding caches.. I found a cache recently that was 50' off from where my GPSr was pointing. When I checked the coordinates in Google Earth, they indicated the exact spot my GPSr was taking me.

Also, I figure the GE results will be the same as indicated on the Geocache App map view, and a lot of folks use the app. If the cache is hidden in the second tree past the last light pole on the SE corner of the parking lot, I'd like the icon to appear there on the map view of the app.


I Agree
Posted Image

#7 KeyResults

KeyResults

    Senior Member

  • Senior Members
  • PipPipPip
  • 1,301 posts
  • LocationTomball

Posted 07 September 2014 - 10:54 PM

Beware SEAMS! ;)

 

Google Earth, as a rule, is quite good! You really need to pay attention to those rare circumstances where your hide is on a seam between two images. In some remote areas, the images are still rather dated, and the seams sometimes can throw in an error as much as 300 feet. My favorite example of this was recently eliminated with a satellite image refresh.  Still, it happens and nobody's perfect.

 

You'll know you've found a seam when you clearly move your mouse across your zoomed in screen while noting the coords aren't really changing or they don't seem to be making sense. That's a seam. In the cases where you hit one, it can be a bit frustrating and your on site averaging won't really match up. My advice in those cases is go with your onsite multiple averaging coords since that's what other geocachers will see when they visit your hide.

 

Sometimes, the satellite image of the urban spots will not align to the coords you measure no matter what. At that point it's a tough call imo. So many today, including myself, use a phone and satellite - especially urban caching - and I think most would prefer to see that pin sitting right on whatever structure or tree or newpaper stand vs the GPS coords puting the pin in the street when a choice must be made. Google maps satellite view is what most use in this case, however so I suspect it's a good idea to check it too.


Why am I all sweatty and late? Umm...




0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users