- 189km2 surveyed using only 74 ground reference survey point
- This Pleiades-1B satellite elevation surveying accuracy is accurate to 26cm RMSE, determined by 1,677 survey checkpoints
- March 2010 Pleiades-1B 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 189 square kilometres, was produced over the PhotoSat test area in Eritrea. The elevation grid was made using geophysical processing of 50cm ground resolution stereo satellite photos taken by the CNES Pleiades-1B satellite. The stereo satellite elevation processing was referenced to 74 ground survey point. The elevation surveying accuracy was measured with over 1,000 survey checkpoints.
Eritrea satellite photos:
The pair of stereo Pleiades-1B satellite photos over the Eritrea test area were taken on March 10, 2013 at approximately 11:10 AM local time.
Eritrea elevation grid:
PhotoSat produced a 1m grid of elevations over the entire project area. We processed the stereo Pleiades-1B photos with our geophysical stereo satellite processing system in October, 2016. An image of the 1m elevation grid is shown below.
Ground reference points:
With this accuracy study we are demonstrating that PhotoSat can produce highly accurate Pleiades-1B elevation surveying with only 74 ground reference points. Having as little as 74 ground reference points for a 189km2 satellite surveying project is not uncommon in mining exploration projects.
The locations of the ground reference points in shown on the elevation image below. The ground reference point was determined by fitting the satellite elevation grid to a dense set of ground survey points around a topographic high. This fit was within 25cm horizontal and 5cm vertical.
Accuracy evaluation checkpoints:
The accuracy of the PhotoSat 1m elevation grid was evaluated with 1,677 ground survey checkpoints. These points were originally surveyed for a large mining exploration gravity survey conducted between 2004 and 2008 by MWH Geophysics. The distribution of the elevation check points is shown in the check points figure below.
The elevation checkpoints were surveyed to an accuracy of 2cm using Real Time Kinematic GPS survey equipment. The accuracy checkpoints consist of a 250m by 250m regional grid of points.
Elevation surveying 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 1,677 elevation checkpoints with slopes less than 20% grade have an RMSE of 26cm.