Method for Calibrating Measuring Element, Method for Evaluating Road Surface Properties, and Apparatus for Evaluating Road Surface Properties

An apparatus for evaluating road surface properties provided with a plurality of measuring, elements emitting measuring light and receiving reflected light for performing evaluation by scanning a road surface by the plurality of measuring elements and measuring a separation quantity from a reference plane of the road surface while the apparatus for evaluating road surface properties being moved along a measurement route of the road surface, comprising:

• a means for setting a reference area for performing the calibration and a provisional reference plane on the reference area;
• a means for acquiring a measurement value obtained by each measuring element regarding the reference area;
• a means for producing point cloud data on a separation quantity of the each point from the provisional reference plane on the reference area regarding the reference area;
• a means for producing a reference plane for calibration based upon a statistic of the point cloud data acquired from all of the measuring elements;
• a means for computing a separation quantity from the reference plane for calibration of the statistic about all of the measuring elements;
• a means for determining a measuring element where the separation quantity is maximum of from among all of the measuring elements;
• a means for calibrating the measuring element so as to make a difference between point cloud data produced from a measurement value of the measuring element where the separation quantity is maximum and the reference plane for calibration less than a predetermined threshold;
• a means for producing a new reference plane for calibration from measurement values obtained by all the measuring elements including the calibrated measuring element;
• and
• a means for determining a final calibration value of each measuring elements by repeating computing a separation quantity from the reference plane for calibration of the statistic regarding, all of the measuring elements, determining a measuring element where the separation quality is maximum from among all of the measuring elements, calibrating the measuring element so as to make a difference between point cloud data produced from a measurement value of the measuring element where the separation quantity is maximum and the reference plane for calibration equal to or less than a predetermined threshold, and producing a new reference plane for calibration from all of the measuring elements including the calibrated measuring element until the separation quantities from the reference plane for calibration of the point cloud data obtained by all of the measuring elements become smaller than a predetermined reference value.