GeoEye-1 Product Accuracy - Ortho Imagery and Terrain Data

An area of ~270km² was captured in stereo by the GeoEye-1 satellite for engineering design purposes.

The GeoEye-1 satellite was used to generate accurate 50cm ortho imagery and 2m contours over the site. The purpose of the imagery was for use during preliminary engineering design for an energy project.


Survey accurate ground control points, distributed evenly across the area, were used in the image processing. These points enabled consistent accuracies to be derived throughout the project area. The accuracies achieved after generating both the ortho image and the Digital Terrain Model (DTM) exceeded the client’s expectations. In both vertical and horizontal planes, accuracy results of better then 50cm were achieved.

Contours at 2m intervals are normally created from a DTM with Z accuracy of 0.6m RMS. The GeoEye-1 DTM was found to have an accuracy of 0.39m RMS, which is equivalent to a contour interval of around 1.3m. These results were pleasing to both our client and GeoEye.

Users should note that in practice anyone can generate contours of any interval desired, however, these products may not be ‘fit for purpose’. Most clients should be confident about how accurate their products really are!  From a purist view, the Australian National Standard for Spatial Data Accuracy specification states that DTMs can be used to create contours with an interval approximately 3.25 times the vertical accuracy of the DTM. The results will then conform to the standard of having 90% of the contours within half the contour interval.

“I have looked at the data and it looks great. The current format works perfectly with our design software. Very pleased with this format and the results it provides.”
Mark, Registered Surveyor. 

For more information, visit our satellite imagery webpage.
 
 

Above and below: 2m contours over the site created from 0.5m GeoEye-1 stereo satellite imagery