On September 24, 1999, the first high-resolution commercial nature resource satellite, IKONOS-2, had been successfully launched. This started a new era to the applications of remote sensing. The best resolution of the IKONOS imageries is 0.82m. This imagery provides more detail spatial information than previous satellites. Many high spatial resolution satellites with hyper-spectral imageries will be launched successively by the year of 2002. When the time comes, the application of remotely sensed images in the area of land and sea will certainly be more widespread. Those imageries will be the fundamental data source for digital earth.
The main purpose of this paper is to apply the IKONOS multi-spectral satellite imageries to derive the shallow water depth. Two key studies will be included as follows. The first is to discuss the high-resolution characteristics of IKONOS images and its precise geometrically correction. The other is applying the multi-spectral images to calculate water depth by regression with few field-measured bathymetry. It is anticipated that the high-resolution remote sensing technology will be an alternative tool to the shallow water bathymetric surveying.
The rugged terrain imageries of CARTERRA Geo level in Taipei County were selected and the bundle adjustment was used for precise images geometrically correction. The positioning accuracy is approximate 1.83m for east-west direction, 1.35m for north-south direction, and 1.6m for elevation. If the orthophoto is been rectified by using bundle adjustment method, the horizontal position accuracy of the check points is about 2.04m. In accordance with these results, using bundle adjustment in the CARTERRA Geo level imagery rectification has proved feasible.
In the study of using muti-spectral images to derive the shallow water depth, both simulated data, IKONOS and SPOT satellite images of South Bay in KenTing are used to verify the influence of wave effect in the satellite imageries. By means of the concept of multi-resolution analysis in wavelet theory, the Daubechies D4 coefficients is tried to filter out the wave effect. Significant improvement on the shallow water depth calculation after filtering wave effect is shown in the result. The accuracy of water depth derivation using high resolution is about 30cm for the water depth shallower than 10m. This research proves that derivation of shallow water depth by using high-resolution satellite imagery is feasibility.