A mobile golf practice device adapted for attachment to the bumper of a standard electric golf cart which allows a golfer to practice his or her stroke with the selected club, proximate the actual shot to be played. The programmable data processing circuit supports instructions that include an indication of a selected parameter value set that indicates how a plurality of data values must be arranged for parallel output from a memory. The gradients are normalized based upon an average magnitude of the gradients in a local spatial region with respect to a given pixel under consideration. An air line communicates pressurized air from the air duct to the second tube. Identifying the minimum post spacing may also include using a minimum contrast ratio associated with the image.