Geodätisches SAR zur Höhenmessung von Gezeitenpegelstationen

Kurzfassung

This thesis analyses how small and cheap radar targets can be used for height measurements of tide gauge stations around the Baltic Sea. For the first time reflecting octahedrons, a combination of eight corner reflectors with a common phase centre, are utilized as SAR targets. Four of these octahedrons and one tophat are installed at the geodetic observatory in Wettzell and measured from July to September 2015 with TerraSAR-X staring spotlight and high resolution spotlight modes. The backscattering of the reflectors in different directions enables to combine ascending and descending satellite orbits to get better results for 3D-positions. This is a crucial advantage compared to ordinary corner reflectors. The octahedron shows theoretically and practically higher backscattering values and therefore better localization accuracy than the tophat. The 3D target positions are estimated on the basis of four staring spotlight acquisitions. They have residuals less than 1.7 cm in horizontal position and about 5 cm in height compared to the independent reference coordinates. The mean error of the octahedrons accounts for ±1.6 cm in range und ±3.1 cm in azimuth direction to the estimated 2D position. The residuals of the single measurements for the octahedrons show a high correlation to the large corner reflector already installed in Wettzell. Thus usual SAR errors like atmosphere and satellite orbit are higher than the localization errors of the octahedrons. The tested reflectors are suitable for installation at tide gauge stations, because they are able to measure the vertical land movement, which has to be separated from the sea level. The available models for vertical land movement have one considerable disadvantage: they can only take account of linear movements – unlike measurements. Among these octahedrons are by far the cheapest options. A simulation for the tide gauge station in Oulu (Finland) shows that octahedrons can achieve a height accuracy of 1.5 cm conside