PURPOSE:To obtain an ultrasonic snow-depth meter which measures the snow depth on a road correctly and properly without being influenced by a moving obstacle or the like. CONSTITUTION:This snow-depth meter is provided with a fixed gate circuit 3 which passes the receiving waves only within the measuring range of the preliminarily predicted snow depth, and a snow depth calculating circuit 4 which calculates the snow depth from the propagating time of the receiving waves passing the fixed gate circuit 3. A fixed threshold value is set in the snow depth calculating circuit 4 by adding to or subtracting from the previously calculating data of the snow depth a value which is not shifted in the ordinary falling state of snow. The threshold value is compared with the current calculating data of the snow depth in a threshold value decision circuit 5. If the current data exceeds the threshold value, the data is judged to be abnormal and regarded as invalid. The previous data is consequently output as it is or after it is added more or less. On the other hand, if the current data is within the threshold value, the current data is output as it is.
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