Laser-Acoustic Ice Thickness Measurements (Feasibility Study)
Abstract
Results of this contract show that it is feasible to measure ice thickness using the laser-acoustic technique. The acoustic signals generated in the ice by a CO2 laser are of sufficient strength to be reflected off the ice/ water interface and can be detected by a receiver in the air. The sound pressure level (SPL) of this signal was detected with a microphone in the air as 110 dB re 1 uPa for a laser energy of 6.5 J. Simultaneous detection by a hydrophone in ice and microphone in air yielded a transmission loss across the ice/air interface of 52 dB. An additional loss of 20 dB occurred when there was a 15 cm snow layer on the ice. The ice thickness derived from this technique yielded a value of 1.0 m, while the actual value was measured as 0.76 m. This discrepancy can be explained by a 4 cm height error in the microphone position. Signal/noise calculations indicate that a 50 J laser should be capable of measuring ice thickness of 10 m from an acoustic receiver in an aerodynamic bird that is towed from an altitude of 20 m. An operational system would provide the capability to remotely measure ice thickness with an accuracy of 5-10% from a helicopter. Remote sensing; Induced sound.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 30, 1987
- Accession Number
- ADA221726
Entities
People
- Gail A. Hickman
- John A. Edmonds