**1. Introduction**

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Craters are features commonly used as research landmarks compared with the other landforms such as rocks, mountains, cliffs and many others. Because of their simple and unique geometry and relatively established appearance under different conditions, the authors decided to select craters as ideal landmarks for detection and spacecraft localization. This chapter focuses on identification of craters in terms of their characteristics and detection of these visual features of the moon to determine a safe landing site for a lunar Lander. Cheng et al. proposed using craters as landmarks for navigation purposes because the geometric model grants a robust detection under different lighting conditions. Moreover, craters appear in enough density on most planetary system bodies of interest and they are also known to have fairly stable appearance or shapes over time or under different conditions and environments. These special features make them an appropriate type of landmark to observe. Currently, there is a lot of on-going studies mainly on craters detection and optical navigation systems for the moon and these studies still adopt a complex and similar approach such as detection using the Hough transform method. To part from this limitation, the authors decided to build a simple algorithm for detecting craters on the moon's surface which will detect the craters based on two important measurements including the distance and angle measurements. The advantages of using this approach are threefold: (1) its uncomplicatedness (2) fast detection (3) can be used further in ellipse reconstruction algorithm to determine the position and orientation of the crater. This chapter will discuss the method of employing MATLAB and image processing tool on an optical image as well as the morphological image detection fundamentals. In addition, some geometrical projection analysis in reconstructing an ellipse as a disc will be evaluated in order to obtain the orientation of the disc (crater) for an autonomous optical navigation system.

© 2012 Kamarudin, licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2012 Kamarudin, licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
