M.W.A. van der Kooij

Mapping of sea bottom topography in a multi sensor approach

Three remote sensing methods for obtaining information on sea bottom topography have been investigated: passive optical bathymetry, sun glint observation and radar observation. Optical and microwave remotely sensed data as well as extensive in-situ data, including a detailed bathymetric map, were gathered in a sand wave area off the Dutch coast. These data were compared with each other and with model predictions. The models are based on the current state-of-the-art, with some extensions. Passive optical bathymetry has limited use above the North Sea because of its limited depth range. Sun glint observation of bottom topography is possible, but its practical applicability is limited by the requirement of low wind speeds and cloudless weather. Radar observation with an imaging radar operating at long wavelengths has the highest potential. The agreement between radar data and model predictions is not always good, due to lack of knowledge on the basic processes. However, in cases where there is good agreement, the imaging model can be inverted numerically to retrieve depth information from radar images.<<ETX>>

Airborne interferometric SAR results from mountainous and glacial terrain

In February 1992, the CCRS Interferometric SAR (CCRS C-InSAR system) was flown over a region in the Canadian Rockies. The test site covered part of the Kananaskis Valley and the Spray Lakes Reservoir and included terrain relief changes of over 1500 metres. The test site was imaged from the 4 cardinal points of the compass, however, the relief changes were so extreme that it was not possible to fill in every gap in the derived digital terrain model caused by layover and radar shadow. The DEM results have been checked by comparing the consistency of the results from opposing passes, by comparison with results generated from aerial stereo photography, and by comparison with GPS ground survey sites. It will be shown that the consistency of results from opposing passes is good and the implied system accuracy compares favourably with that obtained by comparison with the reference DEM and ground survey points. Deriving terrain elevation from Arctic glacier covered terrain using aerial stereo photography is difficult because of weather and flight requirements, coupled with the difficulty of identifying tie points in photography of terrain which is snow covered much of the year. To test InSARs ability to map glacial terrain, the CCRS system was flown over a mountainous test site (with over 1600 metres relief change) on Bylot island in the Canadian Arctic. The test has confirmed the suitability of radar interferometric techniques for this type of terrain. Initial results are shown.<<ETX>>

The application of satellite radar interferometry to subsidence monitoring in the Belridge and Lost Hills fields, California

Oil production from weak, compactable, and low permeability diatomite oil reservoirs in the Belridge and Lost Hills fields in California has resulted in subsidence. Previous efforts to monitor subsidence in these fields have included the installation of surveyor monuments. These monuments allowed the comparison of repeated elevation measurements at the monument locations and the installation of permanent arrays of tiltmeters to measure the direction of the gravity vector through time. Since late 1998, repeat-pass interferometric synthetic aperture radar (InSAR) data have been operationally acquired from several satellites and evaluated over the Belridge and Lost Hills fields to monitor subsidence. Because of the temporally and spatially dynamic nature of subsidence in these fields, the customer decided to acquire InSAR data sets approximately monthly over both fields to monitor subsidence rate changes caused by field development and operating practices. ERS-2 and Radarsat have been used. It has been possible to measure subsidence rates across each field. InSAR deformation data have been compared to and validated with a series of GPS monument survey measurements.

Progress in the development of the CCRS along-track interferometer

The CCRS C-band SAR owned and operated by the Canada Centre for Remote Sensing (CCRS) was modified in 1991 to operate in an across-track C-band interferometric mode for derivation of terrain elevation. This mode has now been extended such that the two C-band receivers can be used with two separate, almost identical, antennas aligned in the along-track direction thereby creating a SAR capable of detecting and measuring target radial motion. Two new C(H) antennas have been mounted on the right-hand side of the Convair 580 to form the along-track C-band interferometer. The antennas share a common, rigid, mounting structure and the phase centres are separated by 0.5 m. The primary application for this mode will be in ocean monitoring R&D; SAR wave and wake imaging, measurement of coastal and ocean currents, estimation of pack-ice drift, detection of sub-surface sand waves through current modulation, etc. while the short baseline dictated by the existing radome leads to a relatively low sensitivity to radial motion, approximately 24/spl deg/ per m/s, the time between image formation at the same azimuth geometry is small (less than 2 ms) with respect to typical C-band ocean coherence times (around 50-100 ms). This, combined with a good signal-to-noise ratio, will allow relatively low phase noise on the interferometric products and therefore adequate sensitivity to radial motion for most situations. A description of the new system and of ground and airborne testing are given.<<ETX>>

Results of processing and analysis of large volumes of repeat-pass InSAR data of Vancouver and Mount Meager (B.C.)

A large quantity of ERS InSAR data and several scenes of Radarsat InSAR data were used to study historical deformation at Mount Meager in Northern B.C. The Mount Meager Volcanic Complex is a hazardous area showing an anomalously high frequency of catastrophic slope failures. It is also the location of Canadas most recent explosive volcanic eruption (2350 YBP). The primary objective of processing and analysis of the SAR data was to detect and measure small deformation events on the slopes of the mountain. A similarly large number of repeated ERS SAR scenes collected over the urban area of Vancouver between 1992 and 2000 was selected for InSAR processing. The objective of the project was to investigate the potential of detecting and measuring very small deformation rates (better than 1 mm/yr) and deformation events while taking advantage of the large volume of SAR datasets. The following types of deformation were of specific interest: 1. Stability of the Fraser River Delta 2. Tidal loading 3. Subsidence patterns in urban areas 4. Deformation of individual buildings, bridges and infrastructure. This paper provides some information on the processing methodologies that were employed as well as results and interpretation of the results.

Satellite radar measurements of land subsidence

The potential of satellite borne interferometric measurements for the mapping of slow land subsidence has been investigated. Two test sites, covered by the ERS-1 satellite, were selected in the Netherlands: the provinces of Groningen and Zeeland. In situ measurements on the weather and the actual subsidence were gathered. It is shown that under favourable conditions measurement accuracies for land subsidence in the range of millimetres are feasible. Atmospheric effects together with temporal decorrelation are the major limitations to the accuracy of the technique for this type of long term measurement.The potential of satellite borne interferometric measurements for the mapping of slow land subsidence has been investigated. Two test sites, covered by the ERS-1 satellite, were selected in the Netherlands: the provinces of Groningen and Zeeland. In situ measurements on the weather and the actual subsidence were gathered. It is shown that under favourable conditions measurement accuracies for land subsidence in the range of millimetres are feasible. Atmospheric effects together with temporal decorrelation are the major limitations to the accuracy of the technique for this type of long term measurement.

An update in the evolution of Radarsat1 azimuth Doppler for differential interferometry purposes

Clarifies the use of interferometry on Radarsat-1 in mid- and long-term intervals between two acquisitions, taking into account changes in the evolution of the azimuth Doppler since April 1999 to maximize coherence and signal to noise ratio. This study is based on fine mode acquisition over Piton de la Fournaise volcano (La Re/spl acute/union island) and shows examples of displacement fields of the July 1999 eruption.

A workstation for spaceborne interferometric SAR data

The Atlantis Interferometric SAR (InSAR) Workstation is implemented in the ERGOvista image analysis software framework. It is specially designed for spaceborne repeat-pass interferometric SAR data and provides both research and operational users with a complete set of commands and tools to interact with interferometric SAR data, generate interferometric products and develop new functions. This paper describes the objectives, requirements and technical outline of the InSAR Workstation. Examples of interferometric products are shown using JERS-1 data of the Hyogo Nanbu (Kobe, Japan) earthquake that occurred on January 17 1995.