A system comprising includes a plurality of three dimensional line-scanner LIDAR sensors disposed to provide a set of fanned beams that travel from one horizon into the air to the other horizon arranged to provide a light fence to detect an object that breaks the light fence and a sensor processor connected to the plurality of three dimensional multi-beam line-scanner LIDAR sensors to establish a vector of travel and a velocity of the object that passes through the multi-beam light fence at the location of where the beams are broken.