1 INVESTIGATION OF THE RELIABILITY OF SATELLITE IMAGERY FOR GENERATING SHALLOW WATER DEPTH INFORMATION FOR NAVIGATIONAL PURPOSES

The Red Sea considered to be one of the most dangerous sea’s for navigation. The Saudi territorial waters along the Red Sea are characterised by coral reefs, which cause difficulties for local navigation, specially the coast guard vessels. The responsibilities of Saudi coast guard need safe navigation through out the entire area including the coral reefs area, thus new approach or methods of study have been followed: Two study areas were considered to be under investigation, Rabigh 150km north of Jeddah while the second area Kishran is located 200 km south of Jeddah. IKONOS images acquired for this study was tasked image the acquisition was requested 2 specially for this study with spatial resolution of 4 meters multispectral, the images were processed and georeferenced against control points taken during the field measurements. The field works were carried out during the period of acquisition, dGPS was the positioning system with accuracy of ±5cm, and the depths were measured using HT100 portable “digital echo sounder, which purchased for this purpose. After calibration of satellite images and convert the images from digital number DN to radiance and then finally to reflectance, and after collecting the field depths for both study area, simple linear regression technique has been employed to build suitable models for extracting the estimated depths, these methodology and process led to successful result with accuracy reached 97%. The same process employed under the most unfavourable conditions where the humidity and temperature and water vapour reach the maximum, the results in these conditions were not recommended (65%). As conclusion the results achieved in this study prove that the satellite imagery could play a part in updating navigational charts by deriving bathymetry of shallow water areas, specially the area where the traditional survey could not be covered due to the spread of coral reefs, Islands and underwater obstacles. 1