Map-matching golf navigation system

A method for obtaining accurate measurements of distance of a golf cart equipped with a computerized dead reckoning navigation (DRN) system from features of interest on a hole of a golf course including tee boxes, cups, water hazards, sand traps, rough areas adjacent fairway, and cart path, to assist golfers in playing the hole, wherein the golf course has been surveyed so that fixed positions of at least some of said features including the cart path are known and are part of a map of the course stored in the data base of the computerized DRN system, the DRN system having a capability to detect and indicate the position of said golf cart on the course map by virtue of including at least one wheel sensor on the golf cart from which to encode wheel rotations and thereby determine position and speed of the golf cart and a compass for determining magnetic heading of the golf cart, but said DRN system undergoing a gradual increase in error of indicated position of the golf cart as the cart is driven about the course during play, thereby introducing error buildup into each said measurement of distance of the cart to said features with contribution thereto from each of said wheel sensor and said compass, said method comprising the steps of:

• examining by means of the DRN system whether the golf cart is on or off the cart path during at least part of the time that said cart is in use in play of each hole;
• and
• at a point in time when the cart is determined to be on the cart path during said play, calibrating the DRN system, including Kalman filter processing information derived in said DRN system from driving said cart, to substantially eliminate the built up error and thereby restore accuracy of measurements performed by the DRN system at that point in time by substantially reducing the discrepancy between (a) a point on the cart path determined to be the actual approximate position of the golf cart and (b) the indicated position of the golf cart removed from said point on the cart path.

A method for obtaining accurate measurements of distance of a golf cart equipped with a computerized navigation system from features of interest on a hole of a golf course including tee boxes, cups, water hazards, sand traps, rough areas adjacent fairway, and cart path, to assist golfers in playing the hole, wherein the golf course has been surveyed so that fixed positions of at least some of said features including the cart path are known and are part of a map of the course stored in the data base of the computerized navigation system, the navigation system having a capability to detect and indicate the position of said golf cart on the course map but undergoing a gradual increase in error of indicated position of the golf cart as the cart is driven about the course during play, thereby introducing error buildup into each said measurement of distance of the cart to said features, said method comprising the steps of:

• examining by means of the navigation system whether the golf cart is on or off the cart path during at least part of the time that said cart is in use in play of each hole, including establishing search zones overlying a sequence of respective generally straight line sections of the cart path in a portion of the stored map of the golf course on a display screen in the golf cart, and identifying one of said zones as being the most likely real time location of the golf cart, said search zones being established as substantially rectangular with side boundaries generally parallel to the section of the path within the respective zone and constituting predetermined limits that define the cart as being off path whenever an icon representative of the cart on the display screen is outside said limits;
• and
• at a point in time when the cart is determined to be on the cart path during said play, calibrating the navigation system, including searching successive segments of the cart path in said identified zone to determine the specific segment on which said point on the cart path lies and moving the indicated position of the cart to said point on the cart path, to substantially eliminate the built up error and thereby restore accuracy of measurements performed by the navigation system at that point in time by substantially reducing the discrepancy between (a) a point on the cart path determined to be the actual approximate position of the golf cart and (b) the indicated position of the golf cart removed from said point on the cart path.

A method for obtaining accurate measurements of distance of a golf cart equipped with a computerized navigation system from features of interest on a hole of a golf course including tee boxes, cups, water hazards, sand traps, rough areas adjacent fairway, and cart path, to assist golfers in playing the hole, wherein the golf course has been surveyed so that fixed positions of at least some of said features including the cart path are known and are part of a map of the course stored in the data base of the computerized navigation system, the navigation system having a capability to detect and indicate the position of said golf cart on the course map but undergoing a gradual increase in error of indicated position of the golf cart as the cart is driven about the course during play, thereby introducing error buildup into each said measurement of distance of the cart to said features, said method comprising the steps of:

• examining by means of the navigation system whether the golf cart is on or off the cart path during at least part of the time that said cart is in use in play of each hole;
• and
• at a point in time when the cart is determined to be on the cart path during said play, calibrating the navigation system including searching the data base of cart path segments to locate the segment closest to the indicated position of the golf cart, to substantially eliminate the built up error and thereby restore accuracy of measurements performed by the navigation system at that point in time by substantially reducing the discrepancy between (a) a point on the cart path determined to be the actual approximate position of the golf cart and (b) the indicated position of the golf cart removed from said point on the cart path;
• said searching including:
• starting the search at a section of the cart path on which the golf cart was last indicated to be positioned on the measurement system, and thereafter first searching said section for a segment thereof which lies substantially parallel to the direction of travel of the cart, including:
• searching forward and backward along said section and testing cart path segments there of for substantially the same vector direction as the heading of the golf cart within limits determined by the estimated extent of compass errors and map errors, and
• if a substantial match of vector direction of a segment and heading of the golf cart is found in the course of the search, verifying that the indicated position of the golf cart lies between imaginary lines extending normal to the cart path segment for which said match was found, at the endpoints of said segment, and if multiple segments are found with said substantial match, selecting that one of the multiple segments which lies closest to and within a predetermined distance limit from said indicated position of the golf cart, or,
• if no match is found, or if it is determined that the golf cart has not been on a cart path recently, establishing substantially rectangular search zones overlying the stored map of the golf course, with at least some of the search zones overlapping each other, and searching the cart path segments in only the zone which encompasses the cart's indicated position.

A method of calibrating a golf cart navigation system used to compute and display position of the cart and relative real time distance from the cart to selected features of a golf course on which the cart is used, said method comprising:

• storing a map of the cart path for said golf course in the data base of the navigation system;
• and
• periodically correcting the position of the cart on the golf course as indicated by the navigation system, from a comparison between selected parameters of the indicated cart position and selected parameters of the stored course map, for use in calibrating the navigation system according, at least in part, to the actual real time position of the cart on said course, wherein said comparison is performed by
• establishing an overlay of substantially rectangular search zones along successive sections of the cart path for a portion of the course of interest on the stored map in the navigation system, and
• searching within selected ones of the zones for a cart path segment having a direction and location which are closest to the real time heading and position of the cart, and after said segment is found, verifying that the indicated position of the cart lies within endpoint boundaries established for that segment of the cart path.

A method of calibrating a golf cart navigation system used to compute and display position of the cart and relative real time distance from the cart to selected features of a golf course on which the cart is used, said method comprising:

• storing a map of the cart path for said golf course in the data base of the navigation system;
• and
• periodically correcting the position of the cart on the golf course as indicated by the navigation system, from a comparison between selected parameters of the indicated cart position and selected parameters of the stored course map, for use in calibrating the navigation system according, at least in part, to the actual real time position of the cart on said course;
• said method further including a global positioning satellite (GPS) calibration system, and said comparison constituting a map-matching or map-correlation technique employed as an alternative to the GPS calibration system at least occasionally when the cart is restricted to the cart path.