Advanced Methodology for ASTER DEM Generation

Image matching and water-body-detection methodologies are essential parts of generating good-quality digital elevation model (DEM) data. It is one of the very important results for image matching where 1-D searching in the along-track direction is sufficient to find the maximum correlation point if reconstructed unprocessed Advanced Spaceborne Thermal Emission and Reflection data (Level-1A data) are used as the source data for DEM products. This important situation is obtained from the general formulation of how to make 1-D searching possible. The image matching quality is evaluated for this 1-D searching method. An image correlation kernel size of 5 by 5 is recommended as the most suitable selection for better horizontal resolution with a slight sacrifice of the image matching error. The satellite pointing fluctuation effect on image matching is also evaluated, leading to the conclusion that it does not seriously affect DEM quality. The water-body-detection technique is another core of DEM generation. The low image correlation coefficient, the low reflectance of water in the near-infrared band 3N, and other spectral characteristics of water were used to identify surface water bodies. In addition, water-body size and the standard deviation of the water-body perimeter elevation are limited for consistent detection without misidentification. As a result, the minimum size of a detectable water body is 0.2km².