WorldView-2, Garlock Fault, 1 GCP, 15cm RMSE, August 2016

PhotoSat WorldView-2 stereo satellite surveying accuracy study, Garlock Fault, California, 15cm RMSE

  • 173 km2 surveyed using only one ground reference survey point
  • This WorldView-2 satellite elevation survey is accurate to 15 cm RMSE, determined by comparison to 7414 elevation check points from a highly accurate LiDAR survey
  • April 2010 WorldView-2 stereo satellite photos processed by PhotoSat in August 2016

Gerry Mitchell, P. Geo, Geophysicist, President PhotoSat

August 2016

Summary report below:

A 1m grid of elevation values, covering an area of 173 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-2 satellite. The stereo satellite elevation processing was referenced to one ground survey point. The elevation surveying accuracy was determined by direct comparison to 7414 elevation check points 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-2 stereo satellite survey accuracy study is shown below.

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 August 2016.

Ground reference points:

With this accuracy study we are demonstrating that we can produce highly accurate WorldView-2 surveys with only one ground reference point. Having as few as one ground reference survey point for a 178 km2 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 -0.9m E, 0.8m N and 0.69m in elevation to match the LiDAR data. The global accuracy of most WorldView stereo satellite photos is better than 3 m.

Accuracy evaluation check points:

The accuracy of the PhotoSat 1m survey grid was evaluated with 7414 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 7414 elevation checkpoints with slopes less than 20% grade have an RMSE of 14.8 cm.