Abstract: One of the most commonly used methods for positioning afloat is by measuring ranges from shore stations to the point a float. This technique is widely used on offshore industry (rig placement, pipe lines...etc). The deployment of the shore stations is largely dependent on the configuration of the coastline. The hydrographer finds it is difficult to deploy the desired number of points on the coastline without compromising the factors of strong geometric fix and land path problems. In order to avoid such problems, the acoustic positioning system using satellites and transponders is nowadays used frequently for all offshore engineering projects. In this study, an attempt to determine the optimum range observations to a float point, which could satisfy requirement of coast configuration and meet the accuracy specified.