1. A computer-implemented method of 3D Computer Aided Design (CAD) modeling comprising: receiving laser scan data of a subject facility, the subject facility having various equipment, there being a prior generated 3D CAD model of the subject facility; applying a computer automated analysis to the received laser scan data to rebuild the 3D CAD model of the subject facility, the analysis utilizing design logic of the facility and design logic of equipment; and providing on output the rebuilt 3D CAD model of the subject facility.