Abstract: A system of differential working is provided wherein a controller of a construction machine is provided with a working depth data set and with a design surface data set. A location of the construction machine within a reference system external to the construction machine is determined, for example using a global navigation satellite system. The controller may determine the desired working depth at the current locations of the ends of the working implement from the working depth data set. The controller may determine the desired cross-slope at the current location of the working implement from the design surface data set. The desired working depths and the desired cross-slope may be communicated to a grade control system of the controller.