Abstract:
Optical remote sensing offers an alternative to traditional hydrographic surveys for
measuring water depth, with the advantage that data are collected synoptically over large area. Just one limitation of the remote sensing in the bathymetry field, this technique is only capable applied to the shallow water whereas for the deeper part of the water, remote sensing technique is not capable to map the bathymetry accurately. Bathymetry can only be derived from remote sensing to a maximum depth of 25m in the clearest water, and considerably less in turbid water. Different satellite had been used to derive bathymetry since 1970 such as Landsat and lkonos. But the high spatial resolution of the satellite has limit the detection and analysis of bathymetry. QuickBird satellite imagery which it has 2.4m of spatial resolution for multispectral image was used in this study to acquire the bathymetry of Lang Tengah Island. The fine spatial resolution of the QuickBird satellite has improve the results of the bathymetry acquire as it can discern small object up to 2.4m. There are a lot of method develop to derive bathymetry, this study is only emphasize on two methods, which are linear method (Benny and Dawson method) and ratio method. Both methods require the same pre-processing, that is, geometric correction, atmospheric correction (Dark pixel subtraction method) and masking. But due to some problem encounter, geometric correction was not done in this project. Comparison was made to compare the accuracy of both methods above to map the bathymetry of various bottom types, which is bottom type with different albedo, at Lang Tengah Island. Accuracy was compare by the actual depth and the bathymetry depth acquire by both methods mention above. The results show that the highest accurate band for Benny and Dawson method was band 2 among the three band compare, which it's R2
