| | 287 |
| Study Name: | | Survey Type: |
| CLDS-1999 | | Bathymetry |
| Survey Name: |
| CLDS-1999 PERIODIC MONITORING Bathymetry | | Disposal Site: |
| | CLDS (1995-pres) |
| | Start Date: | 9/11/1999 | End Date: | 9/11/1999 | Collector: | | SAIC |
| Process Description | The bathymetric data were analyzed using SAIC's Hydrographic Data Analysis System (HDAS), |
| | version 1.03. Raw bathymetric data were imported into HDAS, corrected for sound velocity, and |
| | standardized to mean lower low water using the NOAA observed tides. The bathymetric data were |
| | then used to construct depth models of the surveyed area. |
| 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 data were collected with the use of SAIC's Portable Integrated Navigation and Survey |
| | System (PINSS). This system utilizes a Toshiba 3200 series computer to provide real-time navigation, |
| | as well as collect position, depth, and time data for later analysis. A Del Norte Trisponder® System |
| | provided positioning data to an accuracy of ±3 m in the horizontal control NAD 27. Shore stations |
| | were established along the Connecticut coast at the known benchmarks of Stratford Point and |
| | Lighthouse Point. An ODOM DF3200 Echotrac® Survey Fathometer with a narrow beam, 208 kHz |
| | transducer measured individual depths to a resolution of 3.0 cm (0.1 ft.). Depth values transmitted to |
| | INDAS were adjusted for transducer depth. The acoustic returns of the fathometer can reliably |
| | detect changes in depth of 20 cm or greater due to the accumulation of errors introduced by the |
| | positioning system, vertical motion of the survey vessel, changes in sound velocity through the |
| Horizontal Accuracy | Differential Global Positioning System (DGPS) data were used in conjunction with PINSS to position |
| | the survey vessel. A Trimble 4000DSi GPS receiver and a Trimble NavBeacon XL differential beacon |
| | receiver provided DGPS positioning data to PINSS in the horizontal control of North American Datum |
| | of 1983 (NAD 83) to an accuracy of ±5 m. The Coast Guard differential beacon broadcasting from |
| | Montauk Point, Long Island, New York, (293 kHz) was utilized for satellite corrections due to its |
| Vertical Accuracy | An ODOM DF3200 Echotrac® Survey Fathometer with a narrow beam, 208 kHz transducer |
| | measured individual depths to a resolution of 3.0 cm (0.1 ft.). Depth values transmitted to INDAS |
| | were adjusted for transducer depth. The acoustic returns of the fathometer can reliably detect |
| | changes in depth of 20 cm or greater due to the accumulation of errors introduced by the positioning |
| | system, vertical motion of the survey vessel, changes in sound velocity through the water column, |
| 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 |