High Resolution Elevation Data Derived from Stereoscopic CORONA Imagery with Minimal Ground Control: An Approach Using Ikonos and SRTM Data

The first space mission to provide stereoscopic imagery of the Earth’s surface was from the American CORONA spy satellite program from which it is possible to generate Digital Elevation Models (DEMs). CORONA imagery and derived DEMs are of most value in areas where conventional topographic maps are of poor quality, but the problem has been that until recently, it was difficult to assess their accuracy. This paper presents a methodology to create a high quality DEM from CORONA imagery using horizontal ground control derived from Ikonos space imagery and vertical ground control from map-based contour lines. Such DEMs can be produced without the need for field-based ground control measurements which is an advantage in many parts of world where ground surveying is difficult. Knowledge of CORONA image distortions, satellite geometry, ground resolution, and film scanning are important factors that can affect the DEM extraction process. A study area in Syria is used to demonstrate the method, and Shuttle Radar Topography Mission (SRTM) data is used to perform quantitative and qualitative accuracy assessment of the automatically extracted DEM. The SRTM data has enormous importance for validating the quality of CORONA DEMs, and so, unlocking the potential of a largely untapped part of the archive. We conclude that CORONA data can produce unbiased, high-resolution DEM data which may be valuable for researchers working in countries where topographic data is difficult to obtain.