Photogrammetric solftware for the LH Systems ADS40 Airborne Digital Sensors

Airborne linear array sensors present new challenges for photogrammetric software. The push-broom nature of these sensor systems has the potential for very high quality images, but these are heavily influenced by the dynamics of the aircraft during acquisition. Fortunately, highly precise position and attitude measurements have become possible, using today's inertial measuring units (IMUs). This allows image restoration to the sub-pixel level. The sensor discussed in detail here is a "three-line camera" with additional multispectral lines. The three lines are one looking forward, one in the nadir position and one looking backward with respect to the flight path. Extensive software processes are necessary to produce traditional photogrammetric products from a push-broom airborne sensor. The first steps of the ground processing flow are off-loading imagery and supporting data from the mass memory system of the sensor, post-processing of GPS/IMU data and image rectification into stereo-viewable and matchable form. After this processing, the images can be used similarly to classical aerial photography. This includes semi-automated triangulation with and without ground control, DTM production from multiple stereo views, vector extraction in mono and stereo, and orthophoto and mosaic production. The paper analyses the differences to classical photogrammetric processing for all processing steps and closes with a discussion of the advantages and disadvantages of this new type of photogrammetric imagery.

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