| | 300 |
| 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 |