Measuring thickness of layer of water, snow or ice - evaluating reflected EM radiation directed at inclined angle from above surface e.g. road

摘要

A method of measuring the thickness of a film of water, snow or ice on a surface involves directing pulsed l.m. radiation obliquely from above onto the surface and measuring and evaluating the reflected radiation. The transition time difference is measured between pulsed signals reflected at the surface of the covering film and at the covered surface. The film thickness is derived from this time difference. Time resolved signal reception is performed to enable the time difference to be determined from the time variation of the received signal.