This paper describes several problems and solutions which resulted from planning the NOAA Nationa... more This paper describes several problems and solutions which resulted from planning the NOAA National Coastal Wave Program. Although Waverider buoys are well accepted for measurements, standard Waveriders are too limited in range and were found to have too much RF interference for a long term network. These two problems can be overcome by using buoys which have satellite communications. In earlier models of Waveriders, aging caused a low bias in height measurements. Routine calibration is thus necessary although it was not generally used in the past. Phase shifts in Waverider data limit its use in zero- crossing, wave shape, groupiness, or similar types of analyses. Uncertainties in wave measurements cause extremal wave height statistics to have a high bias and wide confidence intervals. These problems are aggravated by short record lengths.
This study investigates the utility of mission-appropriate hydrographic technology and advanced a... more This study investigates the utility of mission-appropriate hydrographic technology and advanced acoustic-processing methods to statistically discriminate T and UT habitats in the Gulf of Alaska (GOA) bottom-trawl survey area. Five selected "blocks", or groups, of stations were chosen to ensure efficient use of ship time and to cover areas that represent depths and slopes commonly encountered during the NMFS bottom-trawl survey. Additionally, International Hydrographic Organization quality bathymetry data were acquired and delivered for nautical chart updates thoughout the study area.
ECDIS is evolving from a two-dimensional static display of chart-related data to a decision suppo... more ECDIS is evolving from a two-dimensional static display of chart-related data to a decision support system capable of providing real-time or forecast information. While there may not be consensus on how this will occur, it is clear that to do this, ENC data and the shipboard display environment must incorporate both depth and time in an intuitively understandable way. Currently, we have the ability to conduct high-density hydrographic surveys capable of producing ENCs with decimeter contour intervals or depth areas. Yet, our existing systems and specifications do not provide for a full utilization of this capability. Ideally, a mariner should be able to benefit from detailed hydrographic data, coupled with both forecast and real-time water levels, and presented in a variety of perspectives. With this information mariners will be able to plan and carry out transits with the benefit of precisely determined and easily perceived underkeel, overhead, and lateral clearances. This paper describes a Hampton Roads Demonstration Project to investigate the challenges and opportunities of developing the "Electronic Chart of the Future." In particular, a three-phase demonstration project is being planned: 1. Compile test datasets from existing and new hydrographic surveys using advanced data processing and compilation procedures developed at the University of New Hampshire's Center for Coastal and Ocean Mapping/Joint Hydrographic Center (CCOM/JHC); 2. Investigate innovative approaches being developed at the CCOM/JHC to produce an interactive time-and tide-aware navigation display, and to evaluate such a display on commercial and/or government vessels; 3. Integrate real-time/forecast water depth information and port information services transmitted via an AIS communications broadcast.
Journal of the Acoustical Society of America, Nov 1, 1967
The results of two comprehensive independent investigations on ambient noise and wind field fluct... more The results of two comprehensive independent investigations on ambient noise and wind field fluctuations versus wind speed are combined to postulate an interconnection between deep water ambient noise and the short term fluctuations about the local mean wind field. The model considers the air/sea interface to be a time changing acoustic impedance and that energy is extracted from the wind field via a turbulent boundary layer. The combined results indicate that for frequencies above 446 cps, the sound pressure level in dB is linearly related to 20 log of the short-term speed fluctuations, and that for lower frequencies down to 112 cps, the SPL approaches this relationship for mean wind speeds above 22 knots. This model affords a reasonable explanation for the observed fact that at high wind speeds, the level of ambient noise is less sensitive to changes in wind speed. Data that represent a direct evaluation of the postulate that ambient noise is physically linked to the kinetic energy of the local wind-speed fluctuations will be presented.
Proceedings of the 2000 National Technical Meeting of The Institute of Navigation, Jan 28, 2000
The National Ocean Service (NOS) is investigating the application of GPS vertical positioning of ... more The National Ocean Service (NOS) is investigating the application of GPS vertical positioning of its waterborne hydrographic survey platforms to the measurement of depths directly on the NOS chart datum of Mean Lower Low Water (MLLW). One of the more difficult problems that the NOS has encountered during exploratory testing of the GPS vertical positioning of survey vessels is the acquisition and maintenance of resolved phase ambiguities (i.e., integers). As a result of poor satellite geometry, sky blockage, the number of visible satellites, and incorrect ambiguity integers, the NOS has found that GPS vertical positions of suitable accuracy are typically available only 85% of the time. Working with The XYZ’s of GPS, methods have been developed that positively impact the robustness of GPS vertical solutions and the allowable separation between the moving survey platform and the reference station(s). During the summer of 1999, a GPS Expedition to Tangier Island in the Chesapeake Bay was conducted to obtain GPS phase observables from a moving survey platform that could be processed in conjunction with phase data from reference stations located at distances ranging from 1 to 100 km. The vessel used for the expedition, the NOS S/V BAY HYDROGRAPHER, was outfitted with two dual frequency receivers (Ashtech Z-12); one antenna was ION NTM 2000, 26-28 January 2000, Anaheim, CA 3 mounted on the bow and the other was mounted near midship on a horizontal bar, well above the cabin. During the GPS Expedition to Tangier Island, investigations were conducted for mapping the geoid, testing an underwater towbody, measuring the effect of vessel speed on the hydrodynamic interaction between the vessel and the water surface, and the robustness of a newly developed algorithm. The paper discusses the several investigations and concludes that the NOS is now closer to being able to fruitfully rely on GPS vertical positions in its hydrographic survey work.
Journal of the Acoustical Society of America, Aug 1, 1968
Three temporal scales of phase stability are evident in shallow-water acoustic propagation of 170... more Three temporal scales of phase stability are evident in shallow-water acoustic propagation of 1700-Hz CW signals transmitted across Block Island Sound.
Alaska Sea Grant, University of Alaska Fairbanks eBooks, 2008
This paper discusses the basics of acoustic remote sensing (ARS), whereby information may be infe... more This paper discusses the basics of acoustic remote sensing (ARS), whereby information may be inferred about the environment through measurements of backscatter. The physical process of backscatter is described with emphasis on the different outcomes that are associated with a variety of common seabed materials. It is shown that the potential information, which can be inferred from measurements of backscatter, depends on the system design. Important system design parameters include acoustic frequency, pulse length, beamwidth, and deployment technique (towed or hull-mounted). The operational deployment of towed sidescan sonar, in particular whether it is towed close to the seabed or towed higher in the water column, can modify the potential utility of the backscatter measurements to habitat mapping.
Simulated waverider data has been processed by a number of correction algorithms. The impact of t... more Simulated waverider data has been processed by a number of correction algorithms. The impact of these algorithms on estimates of long term extrema is assessed.
A current meter intercomparison eqeriment (called CMICE 7 6) was conducted about 6 km off the sou... more A current meter intercomparison eqeriment (called CMICE 7 6) was conducted about 6 km off the southern coast of Long Island near 4Oo47'N, 72O3O'W during February and Mmch, 1976. A total o f 20 curpent meters were depZoyed on s i x moorings s e t i n a roughly linear array paraZZeZ to the local coastline and topography. The instruments included the Aanderaa RCM-4, the AMF VACM, the Brookhaven NationaZ Laboratory spar buoy system using cyZindrical and spherical Marsh-McBirney electromagnetic sensors, the EG&G 850 and CT-3, and the Chesapeake Bay Institute-modified ENDECO 105. Local mean water depth was 27.8 m and cworent meters were clustered near four depth
This paper describes several problems and solutions which resulted from planning the NOAA Nationa... more This paper describes several problems and solutions which resulted from planning the NOAA National Coastal Wave Program. Although Waverider buoys are well accepted for measurements, standard Waveriders are too limited in range and were found to have too much RF interference for a long term network. These two problems can be overcome by using buoys which have satellite communications. In earlier models of Waveriders, aging caused a low bias in height measurements. Routine calibration is thus necessary although it was not generally used in the past. Phase shifts in Waverider data limit its use in zero- crossing, wave shape, groupiness, or similar types of analyses. Uncertainties in wave measurements cause extremal wave height statistics to have a high bias and wide confidence intervals. These problems are aggravated by short record lengths.
This study investigates the utility of mission-appropriate hydrographic technology and advanced a... more This study investigates the utility of mission-appropriate hydrographic technology and advanced acoustic-processing methods to statistically discriminate T and UT habitats in the Gulf of Alaska (GOA) bottom-trawl survey area. Five selected "blocks", or groups, of stations were chosen to ensure efficient use of ship time and to cover areas that represent depths and slopes commonly encountered during the NMFS bottom-trawl survey. Additionally, International Hydrographic Organization quality bathymetry data were acquired and delivered for nautical chart updates thoughout the study area.
ECDIS is evolving from a two-dimensional static display of chart-related data to a decision suppo... more ECDIS is evolving from a two-dimensional static display of chart-related data to a decision support system capable of providing real-time or forecast information. While there may not be consensus on how this will occur, it is clear that to do this, ENC data and the shipboard display environment must incorporate both depth and time in an intuitively understandable way. Currently, we have the ability to conduct high-density hydrographic surveys capable of producing ENCs with decimeter contour intervals or depth areas. Yet, our existing systems and specifications do not provide for a full utilization of this capability. Ideally, a mariner should be able to benefit from detailed hydrographic data, coupled with both forecast and real-time water levels, and presented in a variety of perspectives. With this information mariners will be able to plan and carry out transits with the benefit of precisely determined and easily perceived underkeel, overhead, and lateral clearances. This paper describes a Hampton Roads Demonstration Project to investigate the challenges and opportunities of developing the "Electronic Chart of the Future." In particular, a three-phase demonstration project is being planned: 1. Compile test datasets from existing and new hydrographic surveys using advanced data processing and compilation procedures developed at the University of New Hampshire's Center for Coastal and Ocean Mapping/Joint Hydrographic Center (CCOM/JHC); 2. Investigate innovative approaches being developed at the CCOM/JHC to produce an interactive time-and tide-aware navigation display, and to evaluate such a display on commercial and/or government vessels; 3. Integrate real-time/forecast water depth information and port information services transmitted via an AIS communications broadcast.
Journal of the Acoustical Society of America, Nov 1, 1967
The results of two comprehensive independent investigations on ambient noise and wind field fluct... more The results of two comprehensive independent investigations on ambient noise and wind field fluctuations versus wind speed are combined to postulate an interconnection between deep water ambient noise and the short term fluctuations about the local mean wind field. The model considers the air/sea interface to be a time changing acoustic impedance and that energy is extracted from the wind field via a turbulent boundary layer. The combined results indicate that for frequencies above 446 cps, the sound pressure level in dB is linearly related to 20 log of the short-term speed fluctuations, and that for lower frequencies down to 112 cps, the SPL approaches this relationship for mean wind speeds above 22 knots. This model affords a reasonable explanation for the observed fact that at high wind speeds, the level of ambient noise is less sensitive to changes in wind speed. Data that represent a direct evaluation of the postulate that ambient noise is physically linked to the kinetic energy of the local wind-speed fluctuations will be presented.
Proceedings of the 2000 National Technical Meeting of The Institute of Navigation, Jan 28, 2000
The National Ocean Service (NOS) is investigating the application of GPS vertical positioning of ... more The National Ocean Service (NOS) is investigating the application of GPS vertical positioning of its waterborne hydrographic survey platforms to the measurement of depths directly on the NOS chart datum of Mean Lower Low Water (MLLW). One of the more difficult problems that the NOS has encountered during exploratory testing of the GPS vertical positioning of survey vessels is the acquisition and maintenance of resolved phase ambiguities (i.e., integers). As a result of poor satellite geometry, sky blockage, the number of visible satellites, and incorrect ambiguity integers, the NOS has found that GPS vertical positions of suitable accuracy are typically available only 85% of the time. Working with The XYZ’s of GPS, methods have been developed that positively impact the robustness of GPS vertical solutions and the allowable separation between the moving survey platform and the reference station(s). During the summer of 1999, a GPS Expedition to Tangier Island in the Chesapeake Bay was conducted to obtain GPS phase observables from a moving survey platform that could be processed in conjunction with phase data from reference stations located at distances ranging from 1 to 100 km. The vessel used for the expedition, the NOS S/V BAY HYDROGRAPHER, was outfitted with two dual frequency receivers (Ashtech Z-12); one antenna was ION NTM 2000, 26-28 January 2000, Anaheim, CA 3 mounted on the bow and the other was mounted near midship on a horizontal bar, well above the cabin. During the GPS Expedition to Tangier Island, investigations were conducted for mapping the geoid, testing an underwater towbody, measuring the effect of vessel speed on the hydrodynamic interaction between the vessel and the water surface, and the robustness of a newly developed algorithm. The paper discusses the several investigations and concludes that the NOS is now closer to being able to fruitfully rely on GPS vertical positions in its hydrographic survey work.
Journal of the Acoustical Society of America, Aug 1, 1968
Three temporal scales of phase stability are evident in shallow-water acoustic propagation of 170... more Three temporal scales of phase stability are evident in shallow-water acoustic propagation of 1700-Hz CW signals transmitted across Block Island Sound.
Alaska Sea Grant, University of Alaska Fairbanks eBooks, 2008
This paper discusses the basics of acoustic remote sensing (ARS), whereby information may be infe... more This paper discusses the basics of acoustic remote sensing (ARS), whereby information may be inferred about the environment through measurements of backscatter. The physical process of backscatter is described with emphasis on the different outcomes that are associated with a variety of common seabed materials. It is shown that the potential information, which can be inferred from measurements of backscatter, depends on the system design. Important system design parameters include acoustic frequency, pulse length, beamwidth, and deployment technique (towed or hull-mounted). The operational deployment of towed sidescan sonar, in particular whether it is towed close to the seabed or towed higher in the water column, can modify the potential utility of the backscatter measurements to habitat mapping.
Simulated waverider data has been processed by a number of correction algorithms. The impact of t... more Simulated waverider data has been processed by a number of correction algorithms. The impact of these algorithms on estimates of long term extrema is assessed.
A current meter intercomparison eqeriment (called CMICE 7 6) was conducted about 6 km off the sou... more A current meter intercomparison eqeriment (called CMICE 7 6) was conducted about 6 km off the southern coast of Long Island near 4Oo47'N, 72O3O'W during February and Mmch, 1976. A total o f 20 curpent meters were depZoyed on s i x moorings s e t i n a roughly linear array paraZZeZ to the local coastline and topography. The instruments included the Aanderaa RCM-4, the AMF VACM, the Brookhaven NationaZ Laboratory spar buoy system using cyZindrical and spherical Marsh-McBirney electromagnetic sensors, the EG&G 850 and CT-3, and the Chesapeake Bay Institute-modified ENDECO 105. Local mean water depth was 27.8 m and cworent meters were clustered near four depth
The Loukkos is among the largest river in Morocco. To date, there has been no thorough investigat... more The Loukkos is among the largest river in Morocco. To date, there has been no thorough investigation of the underwater bedforms in the Loukkos. To characterize variability in bedform geometry, and to provide a detailed description of the morphodynamics of dunes in the river channel, images of the sediment-water interface were collected using an Ocean Server Iver2-62 AUV and an Echosounder 320 BP. Grab samples were taken for understanding sedimentological distribution. Series of bedforms of different sizes are clearly observed in the study area. They are presented as fields developed at depths of 2–10 m. Medium dunes in terms of Ashley's (1990) classification system, are the most dominant. The wavelengths and the heights vary from 1.5 to 52.5 m and 0.3–3.23 m respectively. Overall, the dunes identified along the Oued Loukkos have an asymmetrical cross-section with variable bedforms configuration from 2 D straight crest dunes to sinuous 3D dunes. In addition, the dunes show no clear correlation between dune height and wavelength with depth with previous studies, but this suggest that other parameters should be involved.
2018: Belkhayat, Z., N. Mhammdi, A. Trakadas, L. Huff & F. Medina, New observations of tsunami de... more 2018: Belkhayat, Z., N. Mhammdi, A. Trakadas, L. Huff & F. Medina, New observations of tsunami deposits along the Loukkos estuary; possible evidence for the AD 1755 Lisbon tsunami. In P.P. Cunha, J. Dias, H. Veríssimo, L. V. Duarte, P. Dinis, F.C. Lopes, A.F. Bessa & J.A. Carmo (eds), Atas do IX Simpósio sobre a Margem Ibérica Atlântica, Coimbra, Portugal. Departamento de Ciências da Terra da Universidade de Coimbra: Coimbra: 209-210.
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Papers by Lloyd Huff