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  • 11
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    Laboratory measurements of soil electric properties between 0.1 and 5 GHz (1982)
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
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    Call number: ZSP-201-82/10
    In: CRREL Report, 82-10
    Description / Table of Contents: Dielectric measurements have been performed on silt and sand samples from permafrost areas using Time Domain Reflectometry. The sample temperatures were varied from +25 °C to -25 °C, and volumetric water content was varied between oven-dry and 0.55 gH2O/cm3. The data were processed for frequencies between 0.1 and 5.0 GHz. The results show a constant K' and a low K' for frequencies up to 1 GHz. A frequency dependence seen on the data above 2 GHz is probably the result of unfrozen, adsorbed water. At moisture levels near saturation at all temperatures, these soils have excellent propagation characteristics for ground-probing radar operating below 0.3 GHz. Massive ice should be easily detectable in permafrost within a few degrees of 0 °C.
    Type of Medium: Series available for loan
    Pages: 7 Seiten , Illustrationen
    Series Statement: CRREL Report 82-10
    URL: https://hdl.handle.net/11681/9348
    Language: English
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  • 12
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    Model studies of surface noise interference in ground-probing radar (1979)
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
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    Call number: ZSP-201-85/19
    In: CRREL Report, 85-19
    Description / Table of Contents: Ground-probing radar can be an effective tool for exploring the top 10 to 20 m of ground, especially in cold regions where the freezing of water decreases signal absorption. However, the large electrical variability of the surface, combined with the short wavelengths used, can often cause severe ground clutter that can mask a desired, deeper return. In this study a model facility was constructed consisting of a metallic reflector covered by sand. Troughs of saturated sand were emplaced at the surface to vary surface electrical properties and to act as a noise source to interfere with the bottom reflections. Antenna polarization and height, and signal stacking in both static (antennas stationary) and dynamic (antennas moving) modes were then investigated as methods for reducing the surface clutter. Polarization parallel to the profile direction (perpendicular to the troughs' axes) gave profiles superior to the perpendicular case because of the directional sensitivity of the antenna radiation. Dynamic stacking greatly improved the signal-to-noise ratio because noise sources were averaged as the antennas moved, while the desired reflector, buried at constant depth, was enhanced. Raising the antennas above the surface also reduced noise because the surface area over which reflections were integrated increased. All three noise reduction techniques could be effective in surveys for reflectors at nearly constant depth such as groundwater tables or ice/water interfaces if the lateral variation in undesired ground propertiesis sufficiently random.
    Type of Medium: Series available for loan
    Pages: iv, 23 Seiten , Illustrationen
    Series Statement: CRREL Report 85-19
    URL: https://apps.dtic.mil/dtic/tr/fulltext/u2/a163208.pdf
    URL: https://hdl.handle.net/11681/9440
    Language: English
    Note: CONTENTS Abstract Preface Introduction Objective and procedures Materials and methods Subsurface radar Model facility Results Isolated disturbances-surface and raised analog profiles Multiple disturbances Discussion and conclusions Literature cited
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  • 13
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    Detection of Arctic water supplies with geophysical techniques (1979)
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
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    Call number: ZSP-201-79/15
    In: CRREL Report, 79-15
    Description / Table of Contents: This report discusses the application of several modern geophysical techniques to groundwater exploration in areas in permafrost. These methods utilize the principles of magnetic induction and radiowave surface impedance in the 10- to 400-kHz band, the techniques of impulse and side-looking radar in the 50- to 10,000-MHz band, and also some optical techniques using imagery obtained from a satellite. Low frequency case studies demonstrate the use of the techniques for detecting free water under an ice cover in shallow, almost completely frozen lake basins, and thaw zones within lake beds, stream channels, and in permafrost in general. The radar studies demonstrate the use of these techniques for determining depth of free water and ice cover thickness on lakes and rivers
    Type of Medium: Series available for loan
    Pages: iv, 30 Seiten , Illustrationen
    Series Statement: CRREL Report 79-15
    URL: https://apps.dtic.mil/docs/citations/ADA072157
    URL: https://hdl.handle.net/11681/9012
    Language: English
    Note: CONTENTS Abstract Preface Introduction Part I. Low frequency resistivity methods Resistivity of earth materials Theory and description of techniques Surface impedance technique Airborne radiowave technique Magnetic induction technique Case studies Location of thaw zones beneath lakes and rivers Location of permeable materials in unfrozen ground Delineating permafrost boundaries Part II. High frequency dielectric methods Dielectric properties of earth materials Theory and description of equIpment Profiling radar Imaging radar Case studies Radar profile of a river channel Impulse radar profile of a freshwater lake SLAR imagery of Arctic lakes Literature cited Appendix A: Satellite imagery for subsurface water exploration
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  • 14
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    Short-pulse radar investigations of freshwater ice sheets and brash ice (1986)
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
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    Call number: ZSP-201-86/6
    In: CRREL Report, 86-6
    Description / Table of Contents: Short-pulse radar profiles and waveform traces were recorded over natural, freshwater ice sheets and an artificially made, 1.6-m-diameter column of brash ice. The purpose was to study the feasibility of this type of radar to detect ice thickness, determine ice properties and distinguish ice forms. The radar utilized two antennas: one with a spectrum centered near 900 MHz and a second more powerful one near 700 MHz. Distinct top and bottom reflections from several ice sheets were produced by both antennas, but the value of dielectric permittivity calculated from the time of delay of the reflections varied between sheets as one ice sheet was ready to candle and contained free water. The brash ice distorted signals and allowed no discernible bottom return. The lower frequency antenna also gave returns from the lake bottom (separated from the ice bottom by about 1 m of water), which could allow ice thickness to be determined indirectly. The report concludes that these antennas can be used to determine sheet ice thickness and to supply information to help in the detection of brash ice. The water content of an ice sheet may also be estimated if independent studies show a correlation between dielectric permittivity and free water content.
    Type of Medium: Series available for loan
    Pages: iv, 15 Seiten , Illustrationen
    Series Statement: CRREL Report 86-6
    URL: https://apps.dtic.mil/docs/citations/ADA172578
    URL: https://hdl.handle.net/11681/9429
    Language: English
    Note: CONTENTS Abstract Preface Introduction Materials and methods Sites and site preparation Results and discussion Lake Morey Post Pond Conclusions and recommendations Literature cited
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  • 15
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    Evaluation of the magnetic induction conductivity method for detecting frazil ice deposits (1987)
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
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    Call number: ZSP-201-87/17
    In: CRREL Report, 87-17
    Description / Table of Contents: The ability to map frazil ice deposits and water channels beneath an ice-covered river in central Alaska using the magnetic induction conductivity (MI) technique has been assessed. The study was performed during the first week of March of 1986 on the Tanana River near Fairbanks and employed a commercially available instrument operating at a fixed frequency with a fixed antenna (coil) spacing and orientation. Comparisons of the MI data with theoretical models based upon physical data measured along three cross sections of the river demonstrate the sensitivity of the MI technique to frazil ice deposits. The conductivity generally derived for the frazil ice deposits encountered is very low (approx. .00063 s/m) when compared with the measured value for water (approx. 0.011 S/m), and is similar to the calculated values for gravel and sandy gravel bed sediments. In all three cross sections, maxima in the apparent conductivity profiles correlated with frazil ice deposits. Difficulties, possibly due to adverse effects of cold weather upon instrument calibration, affected the quantitative performance of the instrument on one cross section, although the interpretation of the data (locations of open channels vs frazil deposits) was qualitatively unaffected.
    Type of Medium: Series available for loan
    Pages: iii, 17 Seiten , Illustrationen
    Series Statement: CRREL Report 87-17
    URL: https://apps.dtic.mil/dtic/tr/fulltext/u2/a186940.pdf
    URL: https://hdl.handle.net/11681/9023
    Language: English
    Note: CONTENTS Abstract Preface Introduction Magnetic induction conductivity method Site description and survey methods Cross section field data and modeling results X6 X3A X4 Conclusions and recommendations Literature cited Appendix A: Discussion of errors Appendix B: Modeling data
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  • 16
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    Microwave and structural properties of saline ice (1987)
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
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    Call number: ZSP-201-87/20
    In: CRREL Report, 87-20
    Description / Table of Contents: The structure and salinity characteristics of saline ice slabs removed from ice sheets grown in an outdoor pool have been studied and related to the complex relative dielectric permittivity measured with free-space transmission techniques at 4.80 and 9.50 GHz. The saline ice closely simulated arctic sea ice in its structural and salinity characteristics, which were regularly monitored in a number of ice sheets grown during the winters of 1983-84 and 1984-85. In-situ transmission measurements at similar frequencies were also made on the ice sheets themselves using antennas located above and beneath the ice. The slab measurements were made during warming from -29° to -2°C on slabs grown during the winter of 1983-84 (4.75 GHz) and during a warming and cooling cycle over a slightly larger temperature range on slabs grown during the winter of 1984-85 (4.80 and 9.50 GHz).
    Type of Medium: Series available for loan
    Pages: v, 41 Seiten , Illustrationen
    Series Statement: CRREL Report 87-20
    URL: https://apps.dtic.mil/dtic/tr/fulltext/u2/a189307.pdf
    URL: https://hdl.handle.net/11681/9022
    Language: English
    Note: CONTENTS Abstract Preface Part I - Structural properties Introduction Experimental setup Analytical techniques Results and discussion 1983-84 experiments 1984-85 experiments Conclusions and recommendations Part Il - Microwave properties Introduction Measurement techniques Results 1983-84 experiments 1984-85 experiments 1984-85 in-situ experiments Discussion Comparison of data Analytical modeling Summary and conclusions Literature cited Appendix A: Dielectric mixing model of sea ice
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  • 17
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    Subsurface radar investigations at the Pegasus Glacial-Ice Runway and Williams Field, McMurdo Station, Antarctica (1994)
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
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    Call number: ZSP-201-94/12
    In: CRREL Report, 94-12
    Description / Table of Contents: Subsurface radar was used to profile ice and snow conditions on the Ross Ice Shelf at McMurdo Station, Antarctica, during mid-January 1993. Deconvolution and migration were often used to improve vertical resolution and spatial imaging. Profiles at a pulse center frequency of 400 MHz along the 3.2-km-long Pegasus ice runway show many low-density horizons above 9 m depth that are up to 30 m long. They are associated with air bubbles included during refreezing of meltwater and are interpreted as layers between a few and tens of centimeters thick. There is a strong reflecting horizon at about 9 m depth that is probably from brine intrusion as it is continuous with the intrusion into the snow to the east. Diffraction asymptotes give a dielectric constant near 3.2 for material above the brine level, a value that implies near-solid ice. Profiles at 100 MHz along the road between Pegasus runway and Williams Field in the accumulation zone show snow features such as layer deformation and intrusive brine layers that both abruptly and gradually change in depth. A single profile at a relic solid waste dump at Williams Field detected buried debris and ice within the upper 7 m. A survey of a suspected fuel spill shows some local disturbances near the center, but no excavation was done to verify the findings. Profiles traversing the sewage sumps at Williams Field outline the extent of the sewage deposition, and give depths to contaminated snow that closely agree with observation. Despite variability in dielectric properties, single-layer migration effectively improves the resolution of subsurface conditions. Recommendations are made for future surveys.
    Type of Medium: Series available for loan
    Pages: iv, 29 Seiten , Illustrationen
    Series Statement: CRREL Report 94-12
    URL: https://apps.dtic.mil/dtic/tr/fulltext/u2/a289323.pdf
    URL: https://hdl.handle.net/11681/9377
    Language: English
    Note: CONTENTS Preface Introduction Radar equipment General operation Antennas Waveforms and phase polarity Antenna directivity Field procedures and data processing Field procedures Data recording Data processing Site location Results Pegasus runway Access road from Williams Field to Pegasus runway Williams Field Summary and conclusions Literature cited Appendix A: Airborne profile of a portion of the access road Abstract
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  • 18
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    Airborne radar survey of a brash ice jam in the St. Clair River (1989)
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
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    Call number: ZSP-201-89/2
    In: CRREL Report, 89-2
    Description / Table of Contents: A brash ice jam in the South Channel of the St. Clair River was profiled in February 1987 using a helicopter-borne short-pulse radar operating in the UHF band near 500 MHz. During the same time, measurements of the brash ice depth and water temperature were made from a Coast Guard icebreaker. The returned radar pulses consisted of a strong coherent reflection from the water surface, preceded (and followed) by incoherent returns from the brash ice. The measured waveform time delays were then converted to mean freeboard height of the brash ice pieces above the water surface. Given the mean freeboard height, an estimate of the total brash ice thickness was made. This estimate was greater than the range of the direct shipboard measurements. The difference is believed due to differences between ice porosity above and below the water line, to melting within the ice and to partial submergence of some of the surface pieces. It is concluded that this technique could be used for mapping relative brash ice depth if the complexities of automating waveform analysis could be overcome.
    Type of Medium: Series available for loan
    Pages: iv, 25 Seiten , Illustrationen
    Series Statement: CRREL Report 89-2
    URL: https://apps.dtic.mil/dtic/tr/fulltext/u2/a206868.pdf
    URL: https://hdl.handle.net/11681/9064
    Language: English
    Note: CONTENTS Abstract Preface Introduction Objectives and procedures Equipment Radar Brash ice probe Temperature measurements St. Clair River ice conditions Results and discussion Thickness and temperature Size distribution Radar survey Discussion of errors Porosity Phase state of the ice Partial submergence of individual pieces Spectra of reflected energy Conclusions and recommendations Literature cited Appendix A: Laboratory verification of surface scattering from a simulated ice jam Appendix B: Display of digitized and processed data
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  • 19
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    Investigations of freshwater and ice surveying using short-pulse radar (1991)
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
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    Call number: ZSP-201-91/15
    In: CRREL Report, 91-15
    Description / Table of Contents: 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. In closing, observations on the problems and prospects of this sort of surveying are offered.
    Type of Medium: Series available for loan
    Pages: v, 31 Seiten , Illustrationen
    Series Statement: CRREL Report 91-15
    URL: https://hdl.handle.net/11681/9120
    Language: English
    Note: Contents Preface Nomenclature Introduction Field surveys Methods and paraphernalia Results Sloping bottom effects and critical angle phenomena Deconvolution and thin layers Well-separated echoes Thin ice layers Thin layers of water Observations Literature cited Abstract
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  • 20
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    Measurement of ground dielectric properties using wide-angle reflection and refraction (1982)
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
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    Call number: ZSP-201-82/6
    In: CRREL Report, 82-6
    Description / Table of Contents: The interpretation of continuous radar profiles requires an alternative geophysical means of obtaining ground dielectric information. Ground dielectric properties were measured using wide-angle reflection and refraction (WARR) soundings with a ground-probing radar set that transmits pulses f a few nanoseconds duration. The investigations, carried out over sandy gravel in interior Alaska, provided dielectric data to about a 5-m depth. The WARR soundings were displayed as individual traces allowing interference between separate events and dispersion to be observed, and the soundings were compared with continuous radar and resistivity profiles conducted concurrently to extract the maximum amount of dielectric information. The dielectric constants, derived mainly from the direct ground waves propagating along the surface, ranged from 2.9 to 7.4. Dielectric values interpreted for one site predicted the possibility of a refracted event which may have occurred during one of the soundings.
    Type of Medium: Series available for loan
    Pages: iii, 11 Seiten , Illustrationen
    Series Statement: CRREL Report 82-6
    URL: https://hdl.handle.net/11681/9449
    Language: English
    Note: CONTENTS Abstract Preface Introduction Theory of ground wave propagation from a horizontal electric dipole Equipment and methods Results Site 1 Site 2 Site 3 Summary and concluding remarks Literature cited
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