Abstract
Successfully launched on 30 May 2016, ZY3-02 is the first Chinese surveying and mapping satellite equipped with a lightweight laser altimeter. Calibration is necessary before the laser altimeter becomes operational. Laser footprint location prediction is the first step in calibration that is based on ground infrared detectors, and it is difficult because the sample frequency of the ZY3-02 laser altimeter is 2 Hz, and the distance between two adjacent laser footprints is about 3.5 km. In this paper, we build an on-orbit rigorous geometric prediction model referenced to the rigorous geometric model of optical remote sensing satellites. The model includes three kinds of data that must be predicted: pointing angle, orbit parameters, and attitude angles. The proposed method is verified by a ZY3-02 laser altimeter on-orbit geometric calibration test. Five laser footprint prediction experiments are conducted based on the model, and the laser footprint prediction accuracy is better than 150 m on the ground. The effectiveness and accuracy of the on-orbit rigorous geometric prediction model are confirmed by the test results. The geolocation is predicted precisely by the proposed method, and this will give a reference to the geolocation prediction of future land laser detectors in other laser altimeter calibration test.
Highlights
Elevation measurement accuracy is a major evaluation element of surveying and mapping satellites, and elevation accuracy is a very important factor in surveying and mapping products, such as a digital orthographic model (DOM), digital elevation model (DEM), digital surface model (DSM), etc., [1,2,3]
According to the rigorous geometric prediction model referred to in Equation (1), prediction errors are mainly caused by three factors: laser pointing angle prediction error, orbit prediction error, and attitude prediction error, as well as the ranging error caused by atmospheric delay and tide
Prediction of laser footprint geolocation is a key step for on-orbit geometry calibration of a space-borne laser altimeter based on ground infrared detectors, and has a great influence for following tests to be conducted effectively
Summary
Elevation measurement accuracy is a major evaluation element of surveying and mapping satellites, and elevation accuracy is a very important factor in surveying and mapping products, such as a digital orthographic model (DOM), digital elevation model (DEM), digital surface model (DSM), etc., [1,2,3]. A high-resolution remote sensing, surveying, and mapping satellite system can deliver high precise image products with precise auxiliary data, such as satellite attitude and orbit data. Surveying and mapping satellite always has a small base-to-height ratio less than 1, so elevation measuring accuracy will be a bottleneck in satellite photogrammetry [4,5]. We could apply ground control points (GCPs) or ground elevation control points to reduce elevation error of satellite image products when the covered area was small, but we cannot apply this method to global surveying and mapping [6,7]. We should take some actions to improve elevation accuracy of satellite image products, and meet the demands of highly-precise global surveying and mapping.
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