Tidal flat DEM generation by satellite remote sensing

Abstract

High precision digital elevation model (DEM) in tidal flat is valuable for coastal erosion monitoring. To monitor active coastal changes, a DEM having an accuracy of better than 20 cm is required. We tested two methods: waterline method using optic images and space-borne radar interferometry. Two test sites were selected from Korean tidal flats, Gomso Bay and Saemangeum, and ground truth data have been obtained by leveling in both sites. In the waterline method, band selection was found to be critical especially on the ebb tide, and near infrared was superior to short wavelength infrared. The accuracies of the estimated DEMs were 10.9 cm and 9.8 cm at Gomso Bay and the Saemangeum tidal flat, respectively. We also successfully constructed DEMs using ERS-1/2 tandem pairs. The ERS-1/2 tandem pairs are very useful and as effective as the waterline method. The coherence of the interferogram was generally agreed with the reflectances of Landsat TM bands 4 and 5 with a correlation coefficient of about 0.7. Using sophisticated future spaceborne SAR systems such as Cartwheel, a high precision tidal flat DEM will possibly be constructed if data acquisition plans are properly made.