Google Earth Elevations

[Red Horse]

Anyone have an opinion as to the relative accuracy of the Google Earth elevation figures? +/- ??

 

[woodlandfarms]

How accuate do you need it to be? It is close on our property, compares well to USGS and a LIDAR scan they do now and then in our area, IMO maybe accurate to about 10 feet in all directions,

 

[fordmantpw]

I did a few searches and what I found (from 2-3 years ago) indicated that it is not extremely accurate with a range of +/- 30 meters. Here is one post from 2012: https://www.quora.com/How-accurate-are-relative-elevations-in-Google-Earth

I work with Google Earth application and API every single day. The elevation terrain is not very accurate at all. This is why the licensing terms say that it should not be used as any sort of replacement for surveying or professional use.

The source is apparently SRTM data, run through algorithms to smooth it. That data is only accurate to 30m, which is pretty horrible for anything in which you would need accurate numbers. http://dds.cr.usgs.gov/srtm/version2_1/Documentation/MIL-PDF-89020B.pdf

 

[boggen]

never actually measured or anything. google earth gives idea of "elevation" but with the 2D images messed around and applied to a 3D elevation map... *meh* rotating around some areas, to see a slight hill for water drainage in say a field. *shakes head no* one view you might see hill more so due to 2D image. but rotate it just a bit more. and the slight hill you never see, compared if you were physically at site with feet on ground looking. i can see trees, water ways / creeks, vehicles, buildings, fence row might show up. but elevation overall would say not very accurate. but accurate enough to get an overview of things.

 

[Red Horse]

Well guys I dragged my transit out and shot a point in front of my garage then ran a tape 90' down the drive. 3'3" at the garage and 7'11.5" at the 90 ft. mark for a difference of 4'8.5".

According to Google earth, garage elevation is 450' and if I run the cursor down the drive 90' I get 446', or a drop of 4'

Not bad huh? I have to say before I retired if I was scoping a project, I would not hesitate to work up an order of magnitude number using Google Earth but never used the elevation feature-strictly distances and area calculations.

In my case, the starting elevation may not be correct but the difference in the two points is pretty good IMO

 

[bdog]

I survey tens of thousands of points a year with RTK GPS. The elevations I get with it are sub inch. It compares very well with digital elevation models which is what I assume google earth uses. The only places I have seen huge busts is in areas with sharp and drastic elevation changes like on the edge of a small cliff. I have surveyed points a few feet (less than ten) from the edge on top and when I import those coordinates into google earth I sometimes get an elevation similar to down at the bottom. I think this is due to the grid size google earth uses.

All in all the elevations it provides are pretty dang good but I would not rely on them for anything critical.

 

[davesl708]

If you use Google Earth Pro. (which is free now) They state the accuracy for each scan of an area.

 

[Red Horse]

I survey tens of thousands of points a year with RTK GPS. The elevations I get with it are sub inch. It compares very well with digital elevation models which is what I assume google earth uses. The only places I have seen huge busts is in areas with sharp and drastic elevation changes like on the edge of a small cliff. I have surveyed points a few feet (less than ten) from the edge on top and when I import those coordinates into google earth I sometimes get an elevation similar to down at the bottom. I think this is due to the grid size google earth uses.

All in all the elevations it provides are pretty dang good but I would not rely on them for anything critical.

Bdog- I hear you on the accuracy. I used it last week using a visible drainage grate as a reference and it was within inches to a known elevation.

 

[Red Horse]

If you use Google Earth Pro. (which is free now) They state the accuracy for each scan of an area.

Dave-does it suck up any more of your capacity. I'm clueless about such stuff unless I get my kids help. I use a Mac Book Pro.

 

[davesl708]

Dave-does it suck up any more of your capacity. I'm clueless about such stuff unless I get my kids help. I use a Mac Book Pro.

You do have to download it and run from your hard drive. I think it takes 103 meg. of space. Not a real heavy hit on the CPU or RAM.