InSAR at UC Berkeley

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Berkeley interferogram database

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InSAR is a satellite-based geodetic technique that has gained prominence in tectonic research during the last 15 years. The term stands for Interferometric Synthetic Aperture Radar: processing of the phase information in two SAR images taken of the same area at different times can reveal motion of the ground during the intervening time. Thus, InSAR is useful for measuring ground movements during and after large earthquakes, and also for tracking the slower, continual deformation that occurs between earthquakes. The microwave radiation used in InSAR can penetrate clouds, so the technique is not weather-dependent, and unlike optical imaging methods, it works at night as well as during the day. InSAR has certain advantages over other geodetic techniques such as GPS: for example, it has the potential to provide much denser spatial coverage, and no ground instruments are required.

Four satellites currently collect SAR data around the globe. These data are available from the governing space agencies. The satellites, in order of launch date, are:

ERS-2 (European Remote Sensing Satellite) April 1995 European Space Agency (ESA) Sister satellite to the earlier ERS-1, launched in 1991 and operating until 2000
RADARSAT-1 November 1995 Canadian Space Agency (CSA) RADARSAT-2 is scheduled for launch in December 2007
Envisat March 2002 ESA Advanced version of the earlier ERS satellites
ALOS (Advanced Land Observing Satellite) January 2006 Japan Aerospace Exploration Agency (JAXA) Follow-up to the Japanese Earth Resources Satellite, operational 1992-8

How it Works: Overview

InSAR Resources on the Web

Searching for data

It is possible to search space agency archives online for data availability from the satellites mentioned above:

ROI_PAC Resources

Here at Berkeley we use the open-source ROI_PAC software for processing SAR data to make interferograms. This was first developed at Caltech/JPL during the 1990s and is under ongoing development. Here are some useful ROI_PAC links:

WInSAR Links

"WInSAR is a consortium of universities and research laboratories established by a group of practicing scientists and engineers to facilitate collaboration in, and advancement of, Earth science research using radar remote sensing. WInSAR helps coordinate requests for data acquisition and for data purchase, aiding individual investigators by simplifying interactions with data providers and with government agencies funding science, including NASA, NSF, and the USGS."

Go to the WInSAR archive at UNAVCO.

Getting Started

The following section describes how you can get started in processing your own interferograms at UC Berkeley. Currently we run version 2 of ROI_PAC, built for Linux architecture. Version 3 has been released and should be configured for use very soon.
  1. Add the following to the .cshrc file in your home directory:
    > alias loadroi2 'source /data/voom1/pkgs/ROI_PAC_2_3RC7/SAR_CONFIG_LIN'
  2. Log onto a Linux machine. cd to a directory where you have at least 2 GB of free memory. Many files are created during processing, and some of them are extremely large binary files.
  3. Make a directory called date1_date2, and in that place two further directories called date1 and date2.
  4. Download SAR data from the WInSAR archive, or some other source. Place the data for each date in the directories you have just created.
  5. To source the config file, type:
    > loadroi2
    This sets environment variables and the path for the duration of your current session, so that the ROI_PAC processing scripts can be called compactly from the command line.
  6. Make raw data. In each dateN directory, type:
    > ORBIT_TYPE SARLEADER_FILE dateN (for ERS data), or
    > IMAGE_FILE ORBIT_TYPE dateN (for Envisat data)
    where ERS ORBIT_TYPE is either ODR, PRC or HDR (try them in that order: ODR are Delft precise orbits, PRC are ESA preliminary orbits, and HDR instructs to simply use the orbital information contained in the header file), and Envisat ORBIT_TYPE is DOR (Doris) or HDR.
  7. Download DEM from e.g. USGS seamless distribution and place it in its own DEM directory (this can be placed anywhere). It should have the suffix ".dem".
  8. Return to date1_date2 directory. Copy this template.proc file to the directory. This is a processing script which sets various parameters. Rename it date1-date2.proc and change parameters as appropriate, including the path to your DEM file.
  9. To process the raw data into an interferogram, type:
    > date1-date2.proc raw done
    This will take at least an hour. If you hit problems and can't figure things out, contact Isabelle for help.
Good luck!