293
Study Name:
Survey Type:
NLDS-2000
Bathymetry
Survey Name:
NLDS-2000 POSTCAP Bathymetry
Disposal Site:

NLDS (1995-pres)

Start Date: 8/10/2000 End Date: 8/13/2000 Collector:
SAIC
Process Description The bathymetric data were later processed and analyzed using HYPACK¿s data processing module.

Raw bathymetric data files were corrected for sound velocity within the water column, and

standardized to Mean Lower Low Water (MLLW) using National Oceanographic and Atmospheric

Administration (NOAA) observed tides. The bathymetric data were then used to construct depth

models of the surveyed area for graphical display, as well as to support the presentation of other
Logical Consistency The precise navigation required for all field operations was provided by the SAIC Integrated

Navigation and Data Acquisition System (IDAS). This system uses a Hewlett-Packard 9920 Series

computer to collect position, depth, and time data for subsequent analysis as well as provide real-
Attribute Accuracy Bathymetric surveys are conducted using an integrated navigation system and a Hewlett-Packard

9920 Series computer to collect position, depth, and time data for subsequent analysis as well as

provide real-time navigation. HYPACK was interfaced with an Odom Hydrotrac Fathometer for the

collection of depth soundings over the predetermined survey lines to characterize seafloor

topography. The fathometer was equipped with a narrow beam (3°), 208 kHz transducer.

Approximately 10 measured depth values were collected at a resolution of 1.0 cm, adjusted for

transducer depth, and transmitted to HYPACK within a one-second interval. The fathometer data

recorded by HYPACK were averaged, merged with time and position information, and written to a
Horizontal Accuracy Differentially-corrected Global Positioning System (DGPS) data in conjunction with Coastal

Oceanographic¿s HYPACK® navigation and survey software were used to provide real-time

navigation to an accuracy of ?5 m. A Trimble 4000 RSi GPS receiver was used to obtain raw

satellite data and provide vessel position information in the horizontal control of North American

Datum of 1983 (NAD 83). The GPS receiver was interfaced with a Trimble NavBeacon XL differential

beacon receiver to improve the overall accuracy of the satellite data to the necessary tolerances.

The U.S. Coast Guard differential beacon broadcasting from Monatauk Point, NY (293 kHz) was
Vertical Accuracy HYPACK was interfaced with an Odom Hydrotrac Fathometer for the collection of depth soundings

over the predetermined survey lines to characterize seafloor topography. The fathometer was

equipped with a narrow beam (3°), 208 kHz transducer. Approximately 10 measured depth values

were collected at a resolution of 1.0 cm, adjusted for transducer depth, and transmitted to HYPACK

within a one-second interval. The fathometer data recorded by HYPACK were averaged, merged

with time and position information, and written to a series of navigation log files at a frequency of 2
Depth Datum Name Mean Lower Low Water (MLLW)
Depth Distance Units centimeters
Use Constraints This data was collected and processed for a specific U.S. Army Corps of Engineers activity and

indicates the general existing conditions at the time of collection. As such, the data are only valid for

their intended use, content, time, and accuracy specifications. The user is responsible for the

results of any application of the data for other than the intended purpose.
Contact Person Tom Fredette, Ph.D. Program Manager, US Army Corps of Engineers, New England District

696 Virgina Road, Concord, MA, 01742-2751, Phone:(978) 318-8291 Fax:(978) 318-8303

thomas.j.fredette@usace.army.mil