Evaluation of the TanDEM-X Intermediate DEM for terrain illumination correction in Landsat data
Authors / CoAuthors
Terrain illumination correction is an important step in the normalisation of remotely sensed data for the inversion of land surface parameters, and for applications that aim to detect land surface change through time series analysis. To accurately normalise for the terrain effect, an appropriate resolution of the Digital Elevation Model (DEM) data with sufficient quality is critical for effective correction of remotely sensed data over mountainous areas. Conversely, using terrain illumination correction and scale-based analysis, such as filter bank analysis, the quality of DEM data can be evaluated. In this study, TanDEM-X Intermediate DEM (IDEM) data at 12 m and 30 m resolutions, and the 1-second SRTM data (~ 30 m resolution) were used to evaluate their effectiveness for terrain illumination correction of Landsat satellite data. The island of Tasmania in Australia has a fine scale of terrain detail as well as high relief. The high latitude and strong variability in the terrain illumination throughout the year make it an ideal study site for applying the methods available for this evaluation. Results from the terrain illumination correction and filter bank analysis show that IDEM 12 m and 30 m resolution datasets can resolve finer details of terrain shading than the SRTM based DEMs and deliver better results in the areas with detail-rich terrain. However, since the data available for this study is an intermediate product, spikes and other noise artefacts were prevalent, especially over areas covered by water. Operational use of the IDEM would require the removal of such noise artefacts. The filter bank analysis also found that both Landsat panchromatic data and IDEM 12 m data are oversampled and the signal-to-noise parameters for both DEM and Landsat data are yet to be fully established. Further evaluation of the relative merits of the TanDEM-X based DEM data and the SRTM based DEM data for terrain illumination correction would be possible when the WorldDEM product based on TanDEM-X data becomes routinely available.