Evaluation of adequacy of DEM level-1 as an alternative to level-2: in a context of a case study for radiometric normalization of desert bare soil in Saudi Arabia

摘要

The Kingdom of Saudi Arabia has not yet had a full (national) land cover mapping survey. The very limited areas in Saudi Arabia covered by the 30m resolution DEM level-2 that is compatible with the fine and medium resolution (SPOT and TM) imagery makes it unreliable as a topographic source. The validity of the lower spatial resolution (100m) DEM level-1 of full coverage of the Kingdom as a substitute is tested for that purpose. Two approaches to assessment were considered for this purpose. The first approach, implemented in this paper, involved a comparison between the two DEMs data with the aid of reference data, whereas in the second, not published yet, the assessment was performed on the radiometrically corrected image data using the two DEMs data. Visual and statistical analyses have revealed that differences (discrepancies) between the two DEMs increase with increase of terrain slope, indicating that possibility of DEM level-1 to replace level-2 decreases with increase in terrain slope. The possibility of DEM level-1 to be an adequate alternative to level-2 would apply in flat to moderate terrain (0°- 5°) only, and is expected to decrease as terrain orientation turns away from north (highest differences at 271°- 360°). The differences between the two DEMs for west facing slopes (i.e., 181°-360°) are significantly higher than those for east oriented slopes (i.e., 0° - 180°).