Techniques are disclosed. The techniques include receiving, from a camera, an image showing a portion of a physical topography and target object. The techniques include determining, based on the image, a location of the target object shown in the image and a physical characteristic of the target object shown in the image, the physical characteristic being common with at least another target object. The techniques then include determining a three dimensional (3D) position of the target object in a 3D representation of the portion of the physical topography, the 3D position determined based on (i) the location of the target object, and (ii) the physical characteristic. Based on detecting a cluster of 3D positions of target objects (over several images), the techniques involve generating a 3D boundary of a zone of a portion of the physical topography.