Long Island Sound, NY/CT (M040) Bathymetric Digital Elevation Model (30 meter resolution) Derived From Source Hydrographic Survey Soundings Collected by NOAA

Resource lineage description

source

source description  Source Contribution: Hydrographic Soundings; Source Type: CD-ROM

source citation

Title National Ocean Service- Hydrographic Survey Data

publication  Date   1997-01-01

presentationForm  mapDigital

other Citation Details  Surveys Used in Bathymetry Processing - FE0264, 1984; FE0319, 1988; H05118, 1931; H05220, 1932; H05221, 1932; H05222, 1932; H05333, 1934; H05379, 1933; H05380, 1933; H05382, 1933; H05383, 1933; H05402, 1933; H05407, 1933; H05413, 1933; H05513, 1934; H05514, 1934; H05515, 1934; H05546, 1934; H05547, 1934; H06123, 1934; H06124, 1934; H06125, 1934; H06443, 1939; H07937, 1951; H07938, 1951; H08708, 1962; H08709, 1961; H08908, 1966; H08926, 1966; H08935, 1967; H08936, 1967; H08949, 1967; H08950, 1967; H08951, 1967; H08952, 1967; H08967, 1967; H08996, 1968; H08997, 1968; H09030, 1968; H09051, 1969; H09059, 1969; H09087, 1969; H09088, 1969; H09089, 1969; H09093, 1969; H09181, 1971; H09212, 1971; H10339, 1990; H10346, 1990; H10347, 1990; H10348, 1990; H10349, 1990; H10351, 1990; H10353, 1990; H10354, 1990

cited responsible party - publisher

organisation Name  NOAA, National Environmental Satellite, Data and Information Service (NESDIS), National Geophysical Data Center (NGDC)

Contact information

Address

, Boulder, CO

cited responsible party - originator

organisation Name  National Oceanic and Atmospheric Administration (NOAA), National Ocean Service (NOS), Special Projects

source

source description  Source Contribution: Shoreline position; Source Type: CD-ROM

source citation

Title Medium Resolution Vector Shoreline

publication  Date   1994-01-01

presentationForm  mapDigital

cited responsible party - publisher

organisation Name  NOAA's Ocean Service

Contact information

Address

, Boulder, CO

cited responsible party - originator

organisation Name  National Oceanic and Atmospheric Administration (NOAA), National Ocean Service (NOS)

source

source description  Source Contribution: Ground control points; Source Type: magnetic tape

source citation

Title Project control

publication  Date   1992-05-03

cited responsible party - publisher

organisation Name  U.S. Geological Survey

Contact information

Address

, Reston, VA

cited responsible party - originator

organisation Name  United States Geologic Survey (USGS) or NOAA's National Geodetic Survey (NGS)

AbsoluteExternalPositionalAccuracy

name Of Measure Horizontal Positional Accuracy Report

evaluation Method Description  The horizontal accuracy of the DEM is expressed as an estimated root mean square error (RMSE). The estimate of the RMSE is based upon horizontal accuracy tests of the source soundings used to generate the DEM. As a first approximation the locational accuracy of the source soundings are 0.0015 m at source "Smooth Sheet" scale (120 m @ 1:80,000 to 15 m @ 1:10,000). Smooth Sheets are maps generated as a principle product of each (historic) hydrographic survey with fully corrected soundings plotted on them.

AbsoluteExternalPositionalAccuracy

name Of Measure Horizontal Positional Accuracy

measure Description  Digital elevation models comply with the National Map Accuracy Standards (NMAS) accuracy requirements.

Quantitative Result

result value 3 meters (estimated)

value Units

AbsoluteExternalPositionalAccuracy

name Of Measure Vertical Positional Accuracy Report

evaluation Method Description  The vertical RMSE statistic is used to describe the vertical accuracy of a DEM. It encompasses both random and systematic errors introduced during production of the data. The RMSE is encoded in element number 5 of record C of the DEM. This accuracy estimate includes components related to quantization of the source soundings (1.3 to 0.15 m), the systematic editing of the source data (1percentor 0.10m), un-sampled bathymetric features (estimated at less than 5 percent of depth), time related changes (erosion, deposition, and seismic shifts), and dredging operations (cut and fill). It is estimated that the accuracy of the Bathymetric DEMs is 2 percent of depth or 1 meter for depths greater than 20 meters and 2 percent of depth or 0.20 meters for depths shallower than 20 meters. THESE DEMs SHOULD NOT BE USED FOR NAVIGATION. There are three types of DEM vertical errors: blunder, systematic, and random. These errors are reduced in magnitude by editing but cannot be completely eliminated. Blunders are errors of major proportions and are easily identified and removed during interactive editing. Systematic errors follow some fixed pattern and are introduced by data collection procedures and systems. Systematic error artifacts include vertical unsampled elevation shifts, relative spacing of the source soundings, misinterpretation of terrain surface caused by softness or poor reflectivity and by the resolution of the collected soundings (feet, feet and fractions, fathoms, fathoms and fractions, meters, tenths of meters etc.). Random errors result from unknown or accidental causes. The 1 degree (DSQ) DEMs are generated from 30 m grids on UTM projection. The RMSE difference between these surfaces is an estimate of the vertical accuracy of the DSQ DEMs.

Completeness Commission

evaluation Method Description  The DEM is visually inspected for completeness on a DEM view and edit system for the purpose of performing a final quality control and if necessary, edit of the DEM. The physical format of each DEM is validated for content completeness and logical consistency during production quality control. Due to the variable orientation of the 7 1/2 minute quadrilateral in relation to the Universal Transverse Mercator (UTM) projection grid, profiles that pass within the bounds of the DEM quadrilateral may be void of elevation grid points and are not represented in the DEM. This condition occurs infrequently and is always the first or last profile of the dataset. DEMs may contain void areas caused by elevations being above Mean High Water or on non-tidal land. Void elevations are assigned the value of -32,767. In addition, suspect elevation areas may exist in the DEM but are not specifically identified. Only available data digitized before 1997 were used in this project. Additional sounding information may exist for areas which have holes in the bathymetric data set, but was not available at the time this project was completed. No additional updates or error corrections are planned for this data set.

ConceptualConsistency

measure Description  The fidelity of the relationships encoded in the data structure of the DEM are automatically verified using a NOAA-NOS software program upon completion of the data production cycle. The test verifies full compliance to the DEM specification.