1. A mapping method, comprising: scanning an environment to obtain depth information of environmental obstacles; capturing an image of the environment to generate an image plane; projecting the environmental obstacle depth information onto the image plane, so as to obtain a plurality of projection positions; calculating at least one feature vector from a predetermined range around each of the projection positions in the image plane; combining the depth information of environmental obstacles and each of the feature vectors to generate a sub-map for a certain time point; and combining the sub-maps at all time points to generate a map.