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INTEGRATED AIRBORNE IFSAR MAPPING SYSTEM

A Digital Elevation Model (DEM) is fundamental information for the geo-spatial data infrastructure framework. Many applications require three-dimensional (3-D) geo-spatial data with high spatial resolution and accuracy. One leading technology of the nationwide 3-D mapping is airborne interferometric SAR mapping system due to its all-weather acquisition capability. Compared to other airborne mapping systems, the other advantage of the IFSAR mapping system is the efficiency. Flying at an altitude of 10 km, the Intermap IFSAR system can map an area of 10000 to 20000 km2 per flight. The airborne IFSAR system consists of synthetic aperture radar sensor with two radar antennas and the GPS/INS components. The radar pulse signals are collected from two radar antennas and compressed by digital match filtering to extract the interferometric phase information. The GPS/INS system can provide highly accurate position and orientation information. Combining the SAR interferometric information and the GPS/INS navigation results the ortho-rectified radar image with 3-D information can be obtained. Based on the GPS/INS components of the IFSAR system a new airborne gravity and geoid mapping system is developed by Intermap. The regional geoid undulation can be determined by the airborne gravity system and the ellipsoid height is transformed to the orthometric height directly from the integrated IFSAR system. Thus the integrated IFSAR system can simultaneously provide both sea level referenced DEM data and gravity field information. This opens the application of IFSAR DEM mapping in the rural and mountain areas where accurate gravity data and geoid are not available.