PhotoSat Pleiades-1B stereo satellite surveying accuracy study
Asmara, Eritrea, 1GCP, 28cm RMSE

  • 189km2 surveyed using only one ground reference survey point
  • This PLEIADES-1B satellite elevation surveying accuracy is accurate to 28cm 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
October, 2016

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 one ground survey point. The elevation surveying accuracy was measured with over 1,000 survey checkpoints.

Pleiades-1B colour image with 50cm contours from the PhotoSat Pleiades-1B survey of the Eritrea test area.

Pleiades-1B colour image with 50cm contours from the PhotoSat Pleiades-1B survey of the Eritrea test area.

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 point:

With this accuracy study we are demonstrating that PhotoSat can produce highly accurate Pleiades-1B elevation surveys with only one ground reference point. Having as little as a single ground reference points for a 189km2 satellite surveying project is not uncommon in mining exploration projects.

The location of the ground reference point is 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.

Stereo Pleiades-1B elevation image created from the 1m PhotoSat Asmara, Eritrea satellite survey grid. The figure shows the location of the ground control point.

Stereo Pleiades-1B elevation image created from the 1m PhotoSat Asmara, Eritrea satellite survey grid. The figure shows the location of the ground control point.

Accuracy evaluation checkpoints:

The accuracy of the PhotoSat 1m survey 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. One of the MWH Geophysics survey teams and their equipment are shown below. The accuracy checkpoints consist of a 250m by 250m regional grid of points.

Area of the 14.4km by 13km Eritrea Stereo Pleiades-1B 1m elevation grid showing the location of the ground control point and the 1,677 elevation checkpoints used to determine the accuracy of the stereo satellite survey.

Area of the 14.4km by 13km Eritrea Stereo Pleiades-1B 1m elevation grid showing the location of the ground control point and the 1,677 elevation checkpoints used to determine the accuracy of the stereo satellite survey.

MWH Geo-Surveys differential GPS survey crew and equipment. The Magellan RTK base with a ProMarkTM 500 GPS rover are shown in this photo.

MWH Geo-Surveys differential GPS survey crew and equipment. The Magellan RTK base with a ProMarkTM 500 GPS rover are shown in this photo.

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 a Root Mean Square Error (RMSE) of 28cm.

Histogram of the elevation differences between the Pleiades-1B stereo satellite elevations for the 14km by 13.1km area and the 1,677 elevation checkpoints with slopes less than 20% grade. 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. RMSE 28cm, LE90 47cm.

Histogram of the elevation differences between the Pleiades-1B stereo satellite elevations for the 14km by 13.1km area and the 1,677 elevation checkpoints with slopes less than 20% grade. 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. RMSE 28cm, LE90 47cm.

Learn about PhotoSat's Pleiades-1B survey accuracy.

Download the Eritrea, 1 GCP, 28cm RMSE full report to learn more.

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