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|Title:||Sub-bottom surveying in lakes with ground-penetrating radar|
|Authors:||Sellmann, P. V. (Paul V.)|
Delaney, Allan J.
Arcone, Steven A.
|Publisher:||Cold Regions Research and Engineering Laboratory (U.S.)|
Engineer Research and Development Center (U.S.)
|Series/Report no.:||CRREL report ; 92-8.|
Abstract: Short-pulse radar was used on lakes in New Hampshire for sub-bottom surveying. The objectives were to construct a low-frequency, high-powered antenna suited for this application, and to evaluate the technique under a range of sub-bottom conditions. A compact 50-MHz antenna with a hydrodynamic housing was fabricated for this study. The transmitter provided a peak input power of approximately 1000 W and noise was decreased by submerging the separated antennas on each side of a fiberglass boat to assure consistent coupling. A 100-MHz commercial antenna unit placed in the bottom of the boat and a 7-kHz acoustic sounder, both of which had vertical resolution theoretically comparable or superior to that of the 50-MHz radar, and theoretical studies of antenna directivity were used to help evaluate the results. In shallow water of 1-2 m depth, estimates of the thickness of low density organic sediments (1-4 m thick) over more dense bed material were obtained at both radar frequencies. Noticeable apparent sedimentary bedding and layering, various sediment types and variations in the depth to bedrock beneath the bed were obtained in low-conductivity lake water more than 20 m deep with the higher powered 50-MHz system. Maximum bed penetration was at least 7 m in these cases and vertical bedding resolution was far superior to the acoustic results. Radar bathymetry and limited sub-bottom data were obtained in water up to 30 m deep.
|Appears in Collections:||CRREL Report|