| abstract |
Method and apparatus are disclosed for relatively accurate measurement of the distance of a golf ball to a golf cup, a hazard, or other feature on a hole of a golf course for the purpose of assisting a golfer in playing the hole. The golf course has been surveyed so that relative distances between fixed position coordinates of various features on each hole of the course such as tee boxes, cup placements, water hazards, sand traps, rough terrain, and the like are known. A dead reckoning navigation (DRN) system installed on a golf cart (15) is positioned adjacent a tee box of a hole to be played on the course, as an origin of coordinates for the position of the DRN system; and after a tee shot, the cart (15) is driven to a point adjacent the new position of the ball. As the cart (15) is being repositioned, the coordinates of the new position of the ball relative to the origin are determined from the DRN system. The new position coordinates are used in conjunction with the known distance between the tee box from which the tee shot took place and the cup for the hole being played, to calculate the distance from the new position coordinates to the cup. At some point during play of the course, the DRN system is calibrated to restore accuracy of measurements by substantially removing error buildup from the determination and calculation. The cart (15) may be adapted to communicate with a satellite navigation system such as a global positioning system (14), and to be calibrated using differential GPS (DGPS) information, with Kalman filter processing. The cart-based DRN system has at least one front wheel sensor and a floated or fixed compass, for measuring wheel speed and magnetic heading of the cart, for use in calculating position of the cart on the course. |