Method of mapping ice thickness by fm electromagnetic radiation to indicate shallow thicknesses thereof

Claim 1

Method of dynamically measuring the thickness of ice layers covering a river or a lake in order to determine whether such ice thickness is capable of supporting a continuously moving surface traveling vehicle traversing the upper surface of said ice layer which comprises the steps of: a. positioning an antenna array at a position forward of said continuously moving surface traversing vehicle in the direction of intended travel but closely adjacent to the upper surface of said ice layer, b. radiating, from said position, into said ice layer continuous wave, frequency-modulated electromagnetic energy over a certain frequency range within 106 to 1011 Hertz, c. detecting reflections of said energy from, at least, the bottom of said ice layer, said bottom forming an electromagnetic discontinuity between said ice and said liquid water lying therebelow, said energy being detected by means of said receiving antenna array of said vehicle, d. indicating said reflections from the bottom of the ice, said reflections representing the distance to said ice bottom from said transmitting antenna as measured by the two-way travel time of said energy and interpretable in terms of frequency difference, and e. substantially simultaneous with the in-order occurrence of steps (b)-(d), comparing said frequency difference of said reflected energy with a threshold indication level equivalent to an ice layer thickness which is sufficient to safely support the weight of said vehicle so as to thereby allow determination of whether or not said vehicle can proceed, in safety, along said intended direction of travel.