Investigations of Freshwater and Ice Surveying Using Short-Pulse Radar

• Main Authors: O'Neill, Kevin, Arcone, Steven A.
• Other Authors: COLD REGIONS RESEARCH AND ENGINEERING LAB HANOVER NH
• Format: Text
• Language: English
• Published: 1991
• Subjects: Active & Passive Radar Detection & Equipment; Snow; Ice and Permafrost; AIRBORNE; ALGORITHMS; ANGLES; APPROACH; ATTENUATION; BOTTOM; COUPLING(INTERACTION); FREQUENCY; FRESH WATER; GROUND LEVEL; ICE; INTERFACES; INTERFERENCE; INVERSION; LAYERS; MATCHED FILTERS; PARALLEL ORIENTATION; PATTERNS; RADAR; RADAR EQUIPMENT; RESOLUTION; SHORT PULSES; SIGNAL PROCESSING; SLOPE; SPECTRA; SURVEYS; THICKNESS; THINNESS; TIME DEPENDENCE; ULTRAHIGH FREQUENCY; WATER; WEIGHT; Radar pulses; Search radar; *Radar reflections; *Signal processing; *Ice; Ice openings; PE61102A; PE62784A; AST24; AST42; Ice; permafrost
• Online Access: http://www.dtic.mil/docs/citations/ADA241435; http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA241435

An overview is presented of recent activities and results in the use of commercially available short-pulse UHF radar for surveying ice conditions on freshwater bodies. Improvements in radar systems have made it possible to increase ice thickness resolution by as much as one third relative to that in past attempts, and some new signal processing approaches shown here may offer an order of magnitude improvement. Results from airborne surveying are shown in which the varieties of ice character are reflected. Given the lack of ground coupling, one can rely upon a reasonably well-defined wavelet structure for enhanced signal processing and interpretation possibilities. An algorithm is presented that locates returns from interfaces in the presence of noise for a non-minimum delay wavelet. The method performs a simple inversion in the frequency domain, enhanced by a time dependent weight designed to recognize the shape of the wavelet amplitude and phase spectra. Thin ice layers are resolved down to a few centimeters and are distinguished from an ice free condition by means of a matched filter system designed to recognize the interference pattern from parallel interfaces close to one another. The effects and constraints imposed by water layers on wet ice are discussed, as are general attenuation, sloping bottom, and critical angle effects in deeper water.