Chart Datum-to-Ellipsoid Separation Model Development for Obhur Creek Using Multibeam Hydrographic Surveying

Abstract

A traditional shore-based discrete point chart datum (CD) that represents the lowest astronomical tide (LAT) in Saudi Arabia using tide gauge data is utilized to reduce the observed depth collected from hydrographic surveying test to CD-referenced depth for producing navigation charts for maritime navigation applications. A need for developing CD in a continuous form is essential to replace the traditional discrete CD using tide gauge data. The importance of the development of CD-to-ellipsoid (WGS84) separation model is that it can be utilized by the hydrographers to develop an accurate vertical control for hydrographic surveys applications and can be utilized by the mariners to produce accurate dynamic electronic navigation charts (ENCs). In this paper, a continuous CD to WGS84 ellipsoid separation model for the Sharm Obhur area is developed using a multibeam hydrographic surveying test. It is shown that the continuous chart datum ranges from −4.920 m to −4.766 m and can be achieved with standard deviation ranges from 0.1 cm to 2.3 cm. To validate the separation model, a comparison was made with the gravimetric/oceanographic method based on the separation height developed from geoid height, the sea surface topography and LAT value (chart datum to mean sea level) at the tide gauge located in the study area. The comparison showed that the average value of the developed continuous CD to WGS84 separation model heights using multibeam hydrographic surveying agrees with the separation height estimated from gravimetric/oceanographic method.

Keywords

• LAT
• chart datum
• separation model
• hydrographic surveying
• Sharm Obhur