- 174km2 surveyed using only one ground reference survey point
- This WorldView-1 satellite elevation survey is accurate to 23cm RMSE, determined by comparison to 7,343 elevation check points from a highly accurate LiDAR survey
- June, 2010 WorldView-1 stereo satellite photos processed by PhotoSat in October, 2016
Summary report below:
Gerry Mitchell, P. Geo, Geophysicist, President PhotoSat
A 1m grid of elevation values, covering an area of 174 square kilometres, was produced over a PhotoSat test area in California. The elevation grid was made using geophysical processing of 50cm ground resolution stereo satellite photos taken by the DigitalGlobe WorldView-1 satellite. The stereo satellite elevation processing was referenced to one ground survey point. The elevation surveying accuracy was determined by direct comparison to 7,343 elevation checkpoints extracted from a highly accurate LiDAR survey.
The Garlock Fault was surveyed with LiDAR in April, 2008 by OpenTopography. The location of the LiDAR survey and the area of this WorldView-1 stereo satellite survey accuracy study is shown below. We believe this LiDAR survey data to be accurate to better than 5cm RMSE.
California elevation grid:
PhotoSat produced a 1m grid of elevations over the entire project area. We processed the stereo WorldView photos with our geophysical stereo satellite processing system in October, 2016.
Ground reference points:
With this accuracy study we are demonstrating that we can produce highly accurate WorldView-1 surveys with only one ground reference point. Having as little as one ground reference survey point for a 174km2 satellite surveying project is not uncommon in mining exploration projects.
Global shift of stereo satellite survey to match ground reference:
The WorldView ortho photo and elevation grid needed a constant shift of only 0m E, 1.75m N and 4.34m in elevation to match the LiDAR data. The global accuracy of most WorldView stereo satellite photos is better than 3m.
Accuracy evaluation checkpoints:
The accuracy of the PhotoSat 1m survey grid was evaluated with 7,343 elevation checkpoints derived from the LiDAR elevation grid.
Elevation survey accuracy statistics:
The Guidelines for Digital Elevation Data of the US National Digital Elevation Program (NDEP) recommends that elevation checkpoints should be chosen in areas with slopes less than 20% grade. The 7,343 elevation checkpoints with slopes less than 20% grade have an RMSE of 23cm.