A method of estimating the projected roll distance of a golf ball past an impact point with a target strike plate placed two feet from the golf ball's starting position, the golf ball having been struck by a golfer with a putter, and, conveying the estimated distance and an indication of the golf ball's rolling progress to the golfer comprising the steps of:
- providing a housing that includes a ball impact strike plate, a doppler microwave speed measurement sensor, doppler microwave speed measurement amplifier and schmitt trigger, impact sensor and associated amplifier and schmitt trigger, microcontroller, green speed setting switch, circular memory buffer;
- an internal weight, bumpers mounted on the bottom side of the housing, and a display for outputting the estimated roll distance;
- positioning the housing two feet from the starting position of the golf ball such that the impact strike plate is orthogonal to the intended path of the golf ball so that a golfer can putt a golf ball and cause a collision of the rolling golf ball with the impact strike plate;
- positioning the doppler microwave speed measurement sensor behind the impact strike plate within the housing such that the rolling golf ball is illuminated by the doppler microwave speed measurement sensor which provides an audio output signal indicative of the golf ball's speed;
- amplifying the doppler microwave speed sensor audio output signal and converting the amplified doppler microwave speed sensor audio output signal to a digital signal by connecting it to a schmitt trigger;
- the output of the schmitt trigger connecting to a first interrupt pin of a microcontroller that responds to each negative edge of the microwave speed sensor digital signal, the time between each negative edge being the period;
- positioning an impact sensor within the housing to respond with a signal when the impact strike plate is struck by the rolling golf ball;
- amplifying the impact sensor signal and converting the amplified impact sensor signal to a digital signal by connecting it to a second schmitt trigger;
- the output of the second schmitt trigger connecting to a second interrupt pin of the microcontroller;
- processing the doppler microwave speed sensor digital signal by storing the elapsed time between interrupt negative edges into a circular memory buffer for any movement of any object within the doppler microwave speed sensor's field of view;
- processing the impact detection interrupt by hafting any further interrupts of the doppler microwave speed sensor digital signal, and starting at the most recent elapsed time stored and working backwards, select the newest elapsed time measurements from the circular memory buffer that represent the speed of the rolling ball just prior to impact with the impact strike plate;
- converting the green speed setting switch value into an equivalent coefficient of friction value used in the determination of the golf ball rolling distance estimation step;
- determining the estimated rolling golf ball speed by sorting the elapsed time measurements in descending order from shortest to longest and taking the reciprocal of the average of the second and third shortest elapsed time values;
- the reciprocal, then being multiplied by a doppler microwave speed sensor constant to obtain an estimated rolling golf ball speed in feet per second;
- determining an estimated golf ball rolling distance that the golf ball would have rolled past the impact strike plate by squaring the estimated rolling golf ball speed into a squared estimated speed, and dividing the squared estimated speed by the product of the coefficient of friction multiplied by two times the earth's gravitational constant of acceleration in feet per second per second;
- and,
- outputting a rolling progress indication and the estimated golf ball roll distance to a golfer.