Interferometric Synthetic Aperture Radar (InSAR) is a technique for observing the topographic features and displacements of the Earth's surface by employing SAR satellites. Useful applications of InSAR include measuring the topographic height of the Earth's surface and providing the Digital Elevation Model (DEM). Many scientific observations and investigations require topographical information from DEM, for example, rock mechanics and mining projects, infrastructures and environmental planning, etc. Although the DEM obtained by InSAR can usually cover huge areas of over several hundred square kilometers, it also has the potential to cover smaller areas of only a few square kilometers. In this research, the InSAR technique is applied to generate the DEM of a limestone quarry.
InSAR generates DEM using at least two SAR images which are taken at different times. The existing SRTM or ASTER DEM is used during the co-registration process in InSAR. Taking interferograms using SAR images, DEM is produced under the assumption that there is no displacement of the ground during the SAR observational period. The method is applied here to generate a current DEM of a small area, namely, a limestone quarry with steep slopes. The contour line of DEM obtained by InSAR is compared with those obtained by the existing SRTM and ASTER DEM. It is found that the final DEM obtained by InSAR can produce an appropriate elevation.
The Digital Elevation Model (DEM) provides very important information about the shape (slope and aspect) of a surface. Many scientific observations and investigations require topographical information from DEM, for example, rock mechanics and mining projects, infrastructures and environmental planning, etc. There are many methods/techniques to generate DEM, such as leveling, optical remote sensing, and radar (Yu et al., 2011). The leveling method can provide a very high level of accuracy of DEM, but it will require much time and high labor costs if applied for wide area mapping. Optical remote sensing or photogrammetry can usually provide a moderate level of accuracy of DEM, but if the area of interest is covered by clouds, this technique will be useless. On the other hand, one technique, which uses InSAR (Interferometric Synthetic Aperture Radar), is very useful for generating DEM. It can cover large areas, but is usually applied over a few hundred square kilometers. Since InSAR employs microwave wavelengths, it is independent of weather conditions and can collect data both day and night.