Interferometry
Besides the determination of geophysical parameters there is an essential area of application of the radar with synthetic aperture, the multidimensional mapping of areas. Extracting in particular height information of the corresponding data of a certain a
- PDF / 2,137,596 Bytes
- 42 Pages / 439.2 x 666 pts Page_size
- 98 Downloads / 176 Views
Interferometry
J 5.1 Introduction Besides the determination of geophysical parameters there is an essential area of application of the radar with synthetic aperture, the multidimensional mapping of areas. Extracting in particular height information of the corresponding data of a certain area is interesting. In the field of earth science the exact knowledge of the topography is an important condition to perform and analyse measurements of different kind. For instance, at the framework of earth observing measurements, minimal movements of the earth's crust along tectonic plates are registered. Volcanic eruptions can be predicted by observing topographic height characteristics [SCHW95]. In the meantime, the supply of digital altitude information has become a necessity for applications in the fields of land use planning and environmental observation. It also serves as data base for geo information systems (GIS). Digital height models play also an important role in the fields of processing, analysing and interpretating of corresponding remote sensing data. Especially in the field of geocoding of different input-data bases (Landsat, Spot) digital-height models of the terrain are required. The traditional methods to generate digital-height models basing upon different methods of data recording and modified data processing (tacheometry, digitalising of topographic maps, photogrammetric methods) will soon be obsolete. The application of the more accurate interferometric is more and more advancing. In the future the traditional methods will only be used for special applications.
J 5.2 Theory of SAR interferometry [GRA74] pointed out for the first time the possibility to achieve knowledge concerning the topography of a terrain with the help of the interferometric processing of SAR data. The method of the SAR interferometry, already discussed at the beginning of this work, among others enables us according to [SCHW95] to take advantage of the possibility of measuring the absolute ground level height: A. Hein, Processing of SAR Data © Springer-Verlag Berlin Heidelberg 2004
198
J
Interferometry
J geocoding the recorded data and thus comparing with satellite-based recording systems J the radiometric calibration of SAR images J creation of data bases in geo-information systems. The method of SAR interferometry (also called SARIF or InSAR) is based on the coherence of the radar's signal, the recording of two images of the same area from different perspectives and the utilisation of the phase information of the SAR images. Considering Image 5.1, the conventional SAR method (only sensor 2) point 1 can not be distinguished from point 2 because of rS2P1 = rS2P2. Thus, there is no detectable phase difference of both echo signals. Applying a second sensor this ambiguity is solved (because rS1P1=rS1P2). The phase of the echo signal of point 2 on the sensor is: f1
2p 2rS1P2 f0 k
5:1
On sensor 2 the following phase is measured: f2
2p 2rS2P2 f0 k
5:2
Now forming the phase difference of both signals results in the
Data Loading...
