Does anyone know what Google Earth is using for Elevation in the United States. I did an Elevation Certificate the other day and noticed that the elevations that Google Earth gave were pretty close to what my field measured elevations were (Usually within 1 foot). The county I was in does have LIDAR coverage and it is included in the National Elevation Dataset (NED). Do you think that is what they are using?
The Bow Tie Surveyor
From wikipedia:
"Google Earth uses digital elevation model (DEM) data collected by NASA's Shuttle Radar Topography Mission (SRTM)."
That is one of the sources of the national elevation dataset, so that's probably why it's so close.
I believe that they do use DEM data. We too have found it to be very accurate (sub foot) when we compare it in many places.
This is a great example of how higher accuracy data is becoming more and more avaliable to the public. We need to be able to adapt our business models to take advantage of this and to understand that things are changing. Our county has full aerial 2' contours avaliable... We don't fly or topo many large projects anymore. We do charge (at higher profit margin) the service of incorporating that data into our boundary work.
Another example, we just won a large NYSDEC contact. e are doing the boundary work but major site features such as roads and rivers are to be traced from orthos or supplied from GIS data. Objects within 10 feet of the line still have to be located but that's it.
Tom
From my checks on elevations, some are fairly good and some are fairly bad. Use at your own peril!!!!
John Harmon
At my BM in front of the office, they're off by about 2.5' - 3.5'
> At my BM in front of the office....
Hard to believe my parents paid for all that education, dragged me to the symphony and theater, fostered my religious and moral upbringing, and STILL this is the first thing that came to mind.
I will have to admit that it crosses my mind as well everytime I refer to a BM.
And then in Virginia - the education system has Standards of Learning and of course the acronym is SOL. I know what that stood for when I was growing up - S*** outta luck.
That data set is built with a 30 meter post spacing, so in open flat areas you will likely see good results, but I wouldn't expect good results on a hillside.
> That data set is built with a 30 meter post spacing, so in open flat areas you will likely see good results, but I wouldn't expect good results on a hillside.
I have a 150'x150' drainage retention area in my neighborhood and I can trace the side-slopes on the banks. That's better than 30 meter spacing. I think that they are using the 1/9th arc second (~3 meter spacing) National Elevation Database model that is available in my area.
The Bow Tie Surveyor
That means that your work is still before you.............
not behind you! 😀
10' hills. 1' flats
