In this article, achieving an optimal layout of satellite constellation has been investigated with the aim of navigation (positioning) and with the least amount of error in a region coverage. In navigation, a parameter defined as DOP specifies influences of the geometry of satellite placement in space on position error. Less DOP means more precise navigation, and an attempt has been made in this study to minimize it. In the optimization phase, using genetic algorithm, the number of moments in which coverage is less than four reached zero and then the DOP parameter was minimized. Subsequently, the issue was studied by applying constraints on various orbital elements each time with a certain number of satellites (6 or 7), and the different results were analyzed and compared with each other as well as other navigational systems.