WorldView-3, Garlock Fault, 1 GCP, RMSE, 13cm August 2016

  • 150 km2 surveyed using only one ground reference survey point
  • This WorldView-3 satellite elevation survey is accurate to 13.3 cm RMSE, determined by comparison to 6,854 elevation check points from a highly accurate LiDAR survey
  •  November 2014 WorldView-3 stereo satellite photos processed by PhotoSat in August 2016

 

Summary report below:

Gerry Mitchell, P. Geo, Geophysicist, President PhotoSat

August 2016

A 1m grid of elevation values, covering an area of 150 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-3 satellite. The stereo satellite elevation processing was referenced to one ground survey point. The elevation surveying accuracy was determined by direct comparison to 6,854 elevation check points extracted from a highly accurate LiDAR survey.   

KOMPSAT-3A satellite orthophoto

WorldView-3 color image with 50cm contours from the PhotoSat WorldView-3 survey of the California test area.

LiDAR survey elevation image for satellite survey accuracy study

An elevation image showing the portion of the Opentopography.org LiDAR survey used in this accuracy study. The dimensions of the area are 12.2km east–west by 12km north–south. Lower elevations are blue and higher elevations are red. The oval is the Honda California Test Track

The Garlock Fault was surveyed with a LiDAR in April 2008 by OpenTopography. www.opentopography.org.

WorldView-3 survey grid Garlock Fault California

Stereo WorldView-3 elevation image covering the area of the LiDAR survey. This elevation grid has an elevation point every meter. Low elevations are blue and high elevations are red.

fig13_updated_garlock_wv3_check_points_lt_20_26aug2016

Elevation checkpoints derived from the LiDAR survey for areas with slopes of less than 20% grade.

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-3 surveys with only one ground reference point. Having as few as one ground reference survey point for a 150 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 1.3m E, 0.90m N and -0.94m in elevation to match the ground surveying.  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 6,854 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 6,854 elevation checkpoints with slopes less than 20% grade have an RMSE of 13.3 cm and LE90 21cm

Histogram of WorldView-3 survey accuracy

Histogram of the elevation differences between the WorldView-3 stereo satellite elevations for the 14.4 km by 12 km area and the 6854 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 13 cm, LE90 21 cm.

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