CORONA-IKONOS-2, historical and recent very high resolution satellite data for change detection applications.

The monitoring and explanation of changes is a very basic topic in environmental studies. For certain questions is a very high spatial data resolution important, e.g. in urban or rural settlements. CORONA images were recorded by the United States during cold-war espionage missions between 1960 and 1972. With the KH4B panoramic camera type a ground resolution of 1.8 meters was achieved. The top secret CORONA program was stopped in 1972. Since 1999, SpaceImaging (SI) has been providing data from the IKONOS-2 satellite with 1 meter resolution, which, together with, the CORONA data provides very high resolution satellite time series over a period of more than 40 years. In 1964, starting with the KH4A camera type, CORONA mission satellites carried a second camera on board of the satellite recording stereoscopic images of the earth’s surface. The images were recorded converging with a angle of approximately 30 degrees relative to each other. The CORONA data are delivered as negative or positive films and need a scanning process to take benefit of digital photogrammetry. The commercial software package VirtuoZo allows a data processing in a non-metric way, which makes it possible to calculate a DEM (Digital Elevation Model) out of the CORONA data. Additionally contour lines, a orthophoto and a topographic orthophotomap can be generated. The CORONA-derived orthophoto can be used as a master image for a rectification process of the recent IKONOS-2 data using invariant surface features. Thus, the CORONA-derived orthoimage and the co-registered IKONOS-2 image can be used as a data sources with very high geometric accuracy in real world coordinates in order to detect changes in very high resolution with satellite images over more than 40 years. The study region is located in the southern slopes of the High Atlas mountains in Morocco. Changes can be identified in the neighborhood of settlements, which in some parts have increased enormously, as well as agricultural irrigation areas.