How PhotoSat produces accurate surveys

Application of data processing tools developed for the oil and gas seismic surveying industry

PhotoSat uses data processing algorithms, methods and software tools originally developed for the oil and gas seismic processing industry.

In the 1980’s and 90’s when Gerry Mitchell was working as a Geophysicist in oil and gas exploration he processed a lot of seismic data.  Oil and gas seismic survey data is used to image geological formations thousands of meters below ground in the search for oil and gas.  Seismic data processing has always been one of the most complex and computer intensive data processing fields, with expenditures of billions of dollars annually.

Over the past 50 years seismic processors have developed an immense array of data processing tools.  Gerry knew that this tool box included many tools for automatically matching images, enhancing signals and attenuating noise that could be applied to extracting precise x,y,z survey locations from satellite photos.

Using this different data processing tool box PhotoSat is able to produce elevation grids from satellite photos that are several times more accurate than is produced by conventional satellite and air photo processing methods.

Satellite survey of a river valley processed by conventional photogrammetric methods on the left and by PhotoSat processing on the right. The PhotoSat surveying shows fine topographic detail on the river flood plain that has no expression on the conventional processing.

Satellite survey of a river valley processed by conventional photogrammetric methods on the left and by PhotoSat processing on the right. The PhotoSat surveying shows fine topographic detail on the river flood plain that has no expression on the conventional processing.

Proprietary PhotoSat models of the systematic distortions in stereo satellite photos

PhotoSat has developed proprietary models of the systematic distortions in the photos for most types of commercial stereo satellite systems.   We have measured and characterized these systematic distortions in our test areas. The use of these models in our satellite processing is an essential component of the PhotoSat surveying accuracy.

Adjusting systematic distortions in the stereo satellite photos

To achieve the best possible PhotoSat surveying accuracy, PhotoSat identifies and adjusts the distortions in the satellite photos.  We apply our models of the systematic distortions of each type of satellite photo as follows:

  1. Identify and attenuate distortions in individual stereo pairs of satellite photos
  2. Use overlapping areas of the stereo satellite photos to identify and attenuate distortions in each of the photo pairs.

 

Relative accuracy of 20 cm and global accuracy of 3m after steps 1 and 2

After steps 1 and 2 there is usually 20 cm relative elevation survey accuracy between points separated by up to 10km horizontally.  The global accuracy of all points is usually better than 3m in x, y and z.

 

Achieve absolute accuracy as good as 15cm by using ground survey points

  1. Use ground survey points establish global location and to identify and attenuate specific types of distortions not attenuated in steps 1 and 2.

For more information see the following:

15cm PhotoSat survey accuracy

20cm PhotoSat survey accuracy

30cm PhotoSat survey accuracy

The Accidental Discovery of a New Way to Produce Accurate Elevation Surveys from Satellite Photos 

Are PhotoSat Satellite Surveys Really More Reliable Than Ground Surveys?

How Can Modern Satellites Photos Possibly Be Accurate To 20 Centimeters In 10 Kilometers?

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