1. A method for acquiring three-dimensional (3D) maps, comprising: analyzing at least one image acquired by a passive sensor to identify a plurality of objects in the at least one image; classifying the plurality of objects; determining, based on the classification, whether to passively measure a distance to each of the plurality of objects; passively measuring the distance to at least one of the plurality of objects based on the determination; actively measuring a distance to some of the plurality of objects, wherein the distance to one of the same of the plurality of objects is actively measured when the distance to the object cannot be passively measured; and generating a 3D map of a scene based on the distance measured to each of the plurality of objects.