1. A method of determining the physical dimensions and con-figuration of a structure and/or system comprising: scanning a structure and/or system with an x-ray backscatter unit; collecting data from x-ray photons scattered by the structure and/or system; combining and reconstructing the collected data into a 2-D, 2-D panoramic and/or 3-D data set; generating 3-D surfaces and structures representing hidden objects from the data set; mapping the 3-D surfaces and structures of the hidden objects into a structure and/or system reference coordinate system; combining the 3-D surfaces and structures mapped into the reference coordinate system with models to form a 3-D CAD model of the structure and/or system; and designing modifications to the structure and/or system using the 3-D CAD model.