A method executed by a computer system to construct an omnidirectional roughness (OR) map of a lunar crater based on a data set of a digital elevation model (DEM) of surface textures of the lunar crater is provided. The method includes setting a center and a first point of the data set, selecting a moving window, utilizing a one point-to-point step when the moving window slides over the DEM, calculating a morphological surface roughness (MSR) that detects a vertical roughness of the lunar crater, calculating a topographic frequency coefficient (TFC) that detects a horizontal roughness of the lunar crater, constructing the OR map, and displaying the OR map to show a surface roughness of the lunar crater.