A parameter-free solution is presented for data projector calibration using a single camera and Gray coded structured light patterns. The proposed method assumes that both camera and projector exhibit significant non-linear distortion, and that projection surfaces can be either planar or freeform. The camera is calibrated first through traditional methods, and the calibrated images are then used to detect Gray coded patterns displayed on a surface by the data projector. Projector to camera correspondences are created by decoding the patterns in the camera images to form a 2D correspondence map. Calibrated systems produce geometrically correct, ex- tremely short throw projections, while maintaining or exceeding the projection size of a standard configuration. Qualitative experiments are performed on two baseline images, while quantitative data is recovered from the projected image of a chessboard pattern. A typical throw ratio of 0.5 can be achieved with a pixel distance error below 1.