基于数学形态学的月海圆形撞击坑自动识别方法

Abstract

Identification of lunar crater is very significant, because the crater is not only the most common geological unit on the surface of the moon, but also an important object to study lunar geological evolution history and the fundamental basis of lunar geological dating. This paper conducts to recognize and extract the craters automatically based on mathematical morphology, from the lunar CCD image acquired by the Change I satellite. The grayscale of the crater rims vary obviously in the CCD image, and their gradient are large, which can be calculated to obtain the shape of crater rim. In general, results of crater rims extracted by edge detection based on sharp grayscale gradient of image are discontinuous and rough, and also have gaps and holes. Some processings are further done to take the smooth and continuous arcs of crater rims, by measuring and extracting the corresponding shape from the image with a certain form of structural elements according to the basic idea of mathematical morphology. And then processed arcs may be used to fit the rims of craters conveniently and to obtain the diameters and locations of craters. The algorithm based on mathematical morphology for crater identification is as follows: firstly, we calculate the gradient of grayscale of the CCD image to form a gradient image, and binarize it; then separate the rims by mathematical morphology; finally extract the sizes and locations of craters by fitting rims with circles. In this paper, experiments on identification of craters in lunar mare and terra area show that the algorithm designed by authors may identify the crater with smallest diameter of 10 pixels. The identification of mare craters is accurate and reliable, while of terra craters is a little worse, due to big grayscale variety in CCD image background caused by big lithological differences and fluctuant topography, so we need a futher study on improvement of algorithm.