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Lynch J.F. Newhall A.E. Sperry B. Gawarkiewicz G. Fredricks A. Tyack P. Chiu C.S. Abbot P. 《Oceanic Engineering, IEEE Journal of》2003,28(1):129-150
The spatial and temporal variability of the acoustic field in the region of a strong coastal shelfbreak front are examined, using the high-resolution environmental data from the 1996-1997 New England shelfbreak PRIMER experiment to provide input to acoustic propagation models. Specifically, the "SeaSoar" undulating conductivity-temperature-depth (CTD) probe across-shelf transects provide 1-km along-track resolution, including the front, during the spring, summer, and winter seasons. These data allow one to study the diurnal and seasonal temporal variation of the acoustic field, as well as the varying spatial structure of the field. Using the RAM parabolic equation code, across-shelf acoustic field structure at 200, 400, and 1000 Hz is studied for various source depths. A number of interesting propagation effects are noted, the most interesting of which are the inhibition of strong acoustic-bottom interaction by the warm shelf water beneath the shelfbreak front and the existence of small-scale ducts near the front, due to offshore transport. Data from the vertical line arrays deployed as part of PRIMER offer partial validation of the predictions made. Specifically, it is seen that the mean received levels are in reasonable accord with propagation calculations made using locally measured bottom properties and the SeaSoar water-column measurements. 相似文献
2.
Peter J. Sheulus Richard I. Abbot J. Derral Mulholland 《Celestial Mechanics and Dynamical Astronomy》1975,12(1):57-57
A regular natural satellite observing program has been in operation at McDonald Observatory since late 1972. The observation type has been direct astrometric photography from which the positions of the satellites may be measured with respect to the background star field. Effort has been devoted to the satellite systems of Saturn, Uranus and Neptune as well as the faint outer satellites of Jupiter. To obtain a suitable reference frame, use is being made of the National Geographic-Palomar Sky Survey glass copies as field plates. Through the courtesy of the NASA Skylab SO19 experimenters, the high speed PDS microdensitometer system at the University of Texas at Austin has been made available for our plate measures. The absolute positions of the satellites are determined by the accuracy of the reference frame adopted since catalog star positions are far less accurate than the measures which are obtained. Using SAO catalog positions, for example, we can obtain uncertainties for absolute positions of about 0".3–0".6. Eliminating the dependence on the reference frame by considering only relative satellite measures improves the quoted uncertainties substantially. 相似文献
3.
Yehuda Bock Richard I. Abbot Charles C. Counselman III Robert W. King 《Journal of Geodesy》1986,60(3):241-254
By interferometric analysis ofGPS phase observations made at Owens Valley, Mojave, and Mammoth Lakes, California, we determined the coordinate components of the71–245–313 km triangle of baselines connecting these sites. A separate determination was made on each of four days, April 1–4, 1985. The satellite ephemerides used in these determinations had been derived from observations on other baselines. Therms scatters of the four daily determinations of baseline vector components about their respective means ranged from a minimum of6 mm for the north component of the71-km baseline to a maximum of34 mm for the vertical component of the245-km baseline. To test accuracy, we compared the mean of ourGPS determinations of the245-km baseline between Owens Valley and Mojave with independent determinations by others using very-long-baseline interferometry(VLBI) and satellite laser ranging(SLR). TheGPS-VLBI difference was within 2 parts in10 7 for every vector component. TheGPS-SLR difference was within6 parts in10 8 in the horizontal coordinates, but83 mm in height. 相似文献
4.
Precise long-range kinematic GPS positioning requires the use of carrier phase measurements, the data processing of which suffers from the technical challenges of ambiguity resolution and cycle slip repair. In this paper, the combination of an ambiguity recovery technique and a linear bias correction method has been used to overcome such problems. An experiment was conducted to test the utility of this technique to determine aircraft height to high accuracy, over very long baselines (of the order of one thousand kilometres), in support of the Laser Airborne Depth Sounder (LADS). From a comparison of four independently derived trajectories, this airborne GPS kinematic positioning experiment has confirmed that the sea surface can be determined to centimetre accuracy. The sea surface profiles thus obtained can be used to correct the errors introduced by long period ocean swells. 相似文献
5.
Abbot P. Celuzza S. Dyer I. Gomes B. Fulford J. Lynch J. Gawarkiewicz G. Volak D. 《Oceanic Engineering, IEEE Journal of》2001,26(2):266-284
Environmental acoustics experiments were recently conducted in shallow to intermediate water depths in the Sea of Japan, east of Korea, along the shelf and slope, covering frequencies from 25 to 800 Hz. These were operational experiments carried out in three different seasons. The primary objectives of the data reported here are: (1) to characterize the Korean coastal environment during May 1998, September 1998, and February 1999 and (2) to assess how complexities of the environment might impact acoustic propagation in May and February, as measured by its transmission loss. Propagation data were obtained from broadband explosive SUS sources and sonobuoy receivers. The tests were conducted over varying bottom depths and slopes, both approximately normal and parallel to the bathymetric contours. Two different source depths were included. Environmental and acoustic data are reviewed and discussed. While many aspects of the observed propagation remain ill understood, on the whole a consistent and useful picture has emerged of acoustic propagation in this region. Environmental impacts on propagation are associated mainly with bottom properties, somewhat less so with source depth in relationship to sound speed profiles, and almost not at all with range-dependent profiles of a water mass front 相似文献
6.
Y. Bock R. I. Abbot C. C. Counselman S. A. Gourevitch R. W. King A. R. Paradis 《Journal of Geodesy》1984,58(2):211-221
The Macrometer Model V-1000 is a geodetic positioning instrument that uses the radio signals broadcast by the GPS satellites.
The Macrometer is the only GPS user equipment commercially available that does not require any of the GPS codes. The Model
V-1000 receives only the 19-cm wavelength signals from GPS although similar instruments, built for the U.S. Air Force Geophysics
Laboratory, receive both the 19-and the 24-cm wavelengths. In this paper we summarize the results of two years of field testing
of the V-1000. This instrument, observing four or five satellites fof a few hours, yields a point position accurate within
several meters in each coordinate: latitude, longitude and ellipsoidal height. All three components of the relative position
vector between a pair of points can be determined within 2 parts per million of the distance, given a similar schedule of
observations. This accuracy has been obtained for intersite distances from one kilometer to several thousand kilometers.
Macrometer is a trademark of Aero Service Division, Western Geophysical Company of American, 8100 Westpark Drive, Houston,
Texas, 77063, U.S.A. 相似文献
7.
Sea Surface Determination Using Long-Range Kinematic GPS Positioning and Laser Airborne Depth Sounder Techniques 总被引：3，自引：0，他引：3
Precise long-range kinematic GPS positioning requires the use of carrier phase measurements, the data processing of which suffers from the technical challenges of ambiguity resolution and cycle slip repair. In this paper, the combination of an ambiguity recovery technique and a linear bias correction method has been used to overcome such problems. An experiment was conducted to test the utility of this technique to determine aircraft height to high accuracy, over very long baselines (of the order of one thousand kilometres), in support of the Laser Airborne Depth Sounder (LADS). From a comparison of four independently derived trajectories, this airborne GPS kinematic positioning experiment has confirmed that the sea surface can be determined to centimetre accuracy. The sea surface profiles thus obtained can be used to correct the errors introduced by long period ocean swells. 相似文献
8.
Abbot P. Celuzza S. Dyer I. Gomes B. Fulford J. Lynch J. 《Oceanic Engineering, IEEE Journal of》2003,28(2):192-211
Operational environmental acoustics experiments were conducted over the frequency range of 25 to 800 Hz in September 1997 in the East China Sea, where the water depth was about 100 m. Objectives of the data analysis reported here are to characterize this environment and to assess its complexities as they may impact acoustic propagation as measured by its transmission loss (TL). Conductivity-temperature-depths and expendable bathy-thermographs sampled the ocean, such that its spatial and temporal variability could be approximately separated. The sound-speed profiles are downward refracting, involve two water masses associated with the Kuroshio Current and Taiwan Warm Current, and have thermocline variations caused by internal tides. The bottom geoacoustic characteristics, presumed to be approximately horizontally isotropic, were based on data atlases and were estimated from the measured TL, for some interpretations. The TL data were obtained in octave bands from explosive signal underwater sound sources and sonobuoy receivers, both deployed at a depth of about 18 m. Tests were conducted in directions approximately normal and parallel to the bathymetric contours and the measured TL was, to zero order, independent of the direction of propagation. To higher order, directional differences in the TL were observed and ascribed to anisotropies in bottom properties. A state-of-the-art TL model was adopted, based on environmental idealizations typical of operational forecasting and compared with the measured TL. The comparison yields a probability density function that quantifies the uncertainty of such a TL model, caused by the stochastic variability of the environment, typically unknown a priori. For the model used, the pdf has a standard deviation of about 2 dB from 50 to 800 Hz and larger below 50 Hz. 相似文献
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