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Team: SAR Interferometry

Interferometric methodologies

SAR interferometric methodologies (InSAR) use the phase information contained in every pixel of an image to derive distance measurements with millimeter accuracy. This requires the coherent combination of at least two radar images. The team works in the following main areas:

• Millimeter exact measurement of changes in the earth surface identified in time series
  Surface movements due to occurrences such as earthquakes, slope collapse, groundwater removal or volcanism are measured. In order to identify such small, millimeter-scale movements, an approach called Persistent Scatterer Interferometry (PSI) is primarily used, which allows robust interferometric long-term analysis.
• Production of Digital Elevation Models (DEM) from SAR images obtained from two different recording positions
  An important subject of research is resolving the phase ambiguities (phase unwrapping) among several interferograms.
• Production of three-dimensional tomograms (volumetric images) by combining SAR images from many different recording positions
• Measurement of glacier flow velocities
  Measurements can be reliably accomplished with high-resolution speckle tracking, and very precisely with subsequent interferometric procedures.

The InSAR software system GENESIS was developed by the department for this research and development work. It has a modular structure, and new processing techniques are continuously added as they arise from work related to research projects and master’s and doctoral theses. There are, for example, modules for SAR radargrammetry, speckle tracking, along-track InSAR, split-bandwidth InSAR and SAR tomography.

Other topics of current research are:

SAR radargrammetry is a method employed to measure the 3D location of radar scatterers based on image amplitudes. This makes the processing independent of atmospheric and motion effects and complements interferometric methodologies.

Along-track interferometry makes it possible to measure vehicle velocities. It is used to support traffic monitoring by providing large-area velocity maps.

Split-bandwidth interferometry is a special processing technique which avoids phase ambiguities. It thereby supports the most difficult processing step in DEM generation, namely phase unwrapping.

With the help of interferometric tomography an estimate of motion in a volume can be made for scatters which are essentially indistinguishable.