1. Computer storage media storing computer-executable instructions thereon that, when executed, perform a method of generating a scanned-surface model that represents a scanned surface, the method comprising: receiving a model position of an instrument that is traversed across the scanned surface, wherein the model position identifies a model coordinate of a three-dimensional (3D) model and represents a position of the instrument in the 3D model; deriving, by a range profiler, a set of surface-distance measurements indicating distances of the scanned surface away from the range profiler, wherein the surface-distance measurements are derived as the instrument is traversed across the scanned surface; recording, by an inertial sensor, a set of inertial measurements as the instrument is traversed across the scanned surface; combining the model coordinate, the set of surface-distance measurements, and the set of inertial measurements to calculate a set of scanned-surface model coordinates, wherein the scanned-surface model coordinates represent the scanned surface in the 3D model; and transmitting the scanned-surface model coordinates to a consuming device.