One of the key milestones of radar remote sensing for civil applications
was the launch of the European Remote Sensing Satellite 1 (ERS 1) in
1991. The platform carried a variety of sensors; the Synthetic Aperture
Radar (SAR) is widely cons- ered to be the most important. This active
sensing technique provides all-day and all-weather mapping capability of
considerably ?ne spatial resolution. ERS 1 and its sister system ERS 2
(launch 1995) were primarily designed for ocean app- cations, but soon
the focus of attention turned to onshore mapping. Examples for typical
applications are land cover classi?cation also in tropical zones and mo-
toring of glaciers or urban growth. In parallel, international Space
Shuttle Missions dedicated to radar remote sensing were conducted
starting already in the 1980s. The most prominent were the SIR-C/X-SAR
mission focussing on the investigation of multi-frequency and
multi-polarization SAR data and the famous Shuttle Radar Topography
Mission (SRTM). Data acquired during the latter enabled to derive a DEM
of almost global coverage by means of SAR Interferometry. It is indispe-
ableeventodayandformanyregionsthebestelevationmodelavailable.
Differential SAR Interferometry based on time series of imagery of the
ERS satellites and their successor Envisat became an important and
unique technique for surface defor- tion monitoring. The spatial
resolution of those devices is in the order of some tens of meters.
