well, I have some experience with checking Lidar elevations vs actual topo and the results are less than encouraging. Many shots check about 1/2 ft but I have seen 30 feet or more too. Considering that volume is subject to significant error propagation, I would not take a google earth volume as any better than a guess. Actually, I would take an educated guess over a google earth volume.
> well, I have some experience with checking Lidar elevations vs actual topo and the results are less than encouraging. Many shots check about 1/2 ft but I have seen 30 feet or more too. Considering that volume is subject to significant error propagation, I would not take a google earth volume as any better than a guess. Actually, I would take an educated guess over a google earth volume.
I too have experience checking LiDAR terrain, both that produced by the USGS and by FEMA. I've found bare earth submittal to have "remnants" of first & second returns.
I am not advising to calc volumnes with google nor LiDAR with field verification, but am only pointing out to LiDAR users to review the QC reports, metadata, and certificates.
DDSM
Properly designed volume surveys performed with photogrammetry offer an accuracy of 2%. There is no way to quantify the error envelope for randomly acquired imagery. Such cockamamie quantities would never hold up in court. There's case law existing in North Carolina that was upheld in the State Supreme Court that I testified to. See "State of North Carolina DOTD vs. Halliburton, Brown & Root."
From Wikipedia.
Google Earth uses digital elevation model (DEM) data collected by NASA's Shuttle Radar Topography Mission (SRTM). This means one can view the whole earth in three dimensions. Since November 2006, the 3D views of many mountains, including Mount Everest, have been improved by the use of supplementary DEM data to fill the gaps in SRTM coverage.
If I recall correctly the data within the continental US is published at intervals of 1 arc-second. Everywhere else it's 3 arc-seconds - a data point every 90m or 295 feet.
I've tested this very thing, volumes are so elevation dependent. And from what I've seen Google elevations are between 1-15 feet "off" so............ Good luck with those volumes!!