Cape Fear River, NC (S050) Bathymetric Digital Elevation Model (30 meter resolution) Derived From Source Hydrographic Survey Soundings Collected by NOAA

Bathymetry for the Cape Fear River was derived from seven surveys containing 34,390 soundings. No surveys were omitted. The average separation between soundings was 54 meters. One survey in the south dated from 1934. The remaining six surveys dated from 1970 to 1975. The total range of sounding data was 1.0 meters to -17.3 meters at mean low water. Mean high water values of 1.2 or 1.3 meters were assigned to the shoreline. Five points were found that were not consistent with the surrounding data. These were removed prior to tinning. DEM grid values outside the shoreline (on land) were assigned null values (-32676). The Cape Fear River has seven 7.5 minute DEMs and four one degree DEMs. The 1 degree DEMs were generated from the higher resolution 7.5 minute DEMs which covered the estuary. A Digital Elevation Model (DEM) contains a series of elevations ordered from south to north with the order of the columns from west to east. The DEM is formatted as one ASCII header record (A- record), followed by a series of profile records (B- records) each of which include a short B-record header followed by a series of ASCII integer elevations (typically in units of 1 centimeter) per each profile. The last physical record of the DEM is an accuracy record (C-record). The 7.5-minute DEM (30- by 30-m data spacing) is cast on the Universal Transverse Mercator (UTM) projection. It provides coverage in 7.5- by 7.5-minute blocks. Each product provides the same coverage as a standard USGS 7.5-minute quadrangle but the DEM contains over edge data. Coverage is available for many estuaries of the contiguous United States but is not complete.
Cite this dataset when used as a source.
  • ID not available.
gov.noaa.ngdc.mgg.dem:cape_fear_river_s050_30m
Search Data
Download Data
Distribution Formats
  • netCDF (Version: 4 Classic)
Distributor DEM Information
DOC/NOAA/NESDIS/NCEI > National Centers for Environmental Information, NESDIS, NOAA, U.S. Department of Commerce
dem.info@noaa.gov
Dataset Point of Contact DEM Information
DOC/NOAA/NESDIS/NCEI > National Centers for Environmental Information, NESDIS, NOAA, U.S. Department of Commerce
dem.info@noaa.gov
Time Period 1934-01-01 to 1975-01-01
Spatial Reference System urn:ogc:def:crs:EPSG::586626918
Spatial Bounding Box Coordinates
N: 34.281013
S: 33.866902
E: -77.91167
W: -78.066378
Spatial Coverage Map
General Documentation
Associated Resources
  • NOAA NOS Estuarine Bathymetry
Publication Dates
  • publication: 1998-06-06
Edition First
Data Presentation Form mapDigital
Dataset Progress Status Complete - production of the data has been completed
Data Update Frequency Irregular
Supplemental Information
The datum for these bathymetric DEMs is not the same as that used by the United States Geological Survey (USGS) for land based DEMs which results in a discontinuity if the two datasets are merged together. Moreover, the shoreline for the USGS DEMs is indeterminate and not the same as that used for the Bathymetric DEMs. Because of these differences, extreme care should be used in merging NOAA and USGS DEM data. 7.5-minute DEMs have rows and columns which vary in length and are staggered. The UTM bounding coordinates form a quadrilateral (no two sides are parallel to each other), rather than a rectangle. The user will need to pad out the uneven rows and columns with blanks or flagged data values, if a rectangle is required for the user's application. Some software vendors have incorporated this function into their software for input of standard formatted USGS DEMs. The data within the bathymetry file is floating point. When using the data within a GIS care must be taken to ensure that the data are being read as floating point and not integer data.
Purpose Bathymetric DEM's can be used as layers in Geographic Information Systems (GIS) for earth science analysis. DEM's can also serve as tools for volumetric analysis, for site location of structures, or for drainage basin delineation. The source soundings are collected by the NOS Office of Coast Survey (OCS).
Use Limitations
  • Not to be used for navigation. Although these data are of high quality and useful for planning and modeling purposes, they are not suitable for navigation. For navigation, please refer to the NOS nautical chart series.
  • Produced by the NOAA National Geophysical Data Center. Not subject to copyright protection within the United States.
Originators
  • Department of Commerce (DOC), National Oceanic and Atmospheric Administration (NOAA), National Ocean Service (NOS), Special Projects (SP)
Publishers
  • NOAA's National Ocean Service, Special Projects (SP)
Theme keywords Global Change Master Directory (GCMD) Science Keywords
  • Earth Science > Oceans > Bathymetry/Seafloor Topography > Seafloor Topography
  • Earth Science > Oceans > Bathymetry/Seafloor Topography > Bathymetry
  • Earth Science > Oceans > Bathymetry/Seafloor Topography > Water Depth
  • Earth Science > Oceans > Coastal Processes > Coastal Elevation
Uncontrolled
  • Coastal Relief
  • Gridded elevations
  • Bathymetry
Place keywords None
  • Cape Fear River, NC
  • North Carolina
Data Resolution keywords Global Change Master Directory (GCMD) Horizontal Data Resolution Keywords
  • 1 meter - < 30 meters
Global Change Master Directory (GCMD) Vertical Data Resolution Keywords
  • 1 meter - < 10 meters
Use Constraints No constraint information available
Access Constraints
  • Distribution liability: NOAA and NCEI make no warranty, expressed or implied, regarding these data, nor does the fact of distribution constitute such a warranty. NOAA and NCEI cannot assume liability for any damages caused by any errors or omissions in these data. If appropriate, NCEI can only certify that the data it distributes are an authentic copy of the records that were accepted for inclusion in the NCEI archives.
Fees Fee information not available.
Lineage information for: dataset
Processor
  • DOC/NOAA/NESDIS/NCEI > National Centers for Environmental Information, NESDIS, NOAA, U.S. Department of Commerce
Processing Steps
  • The production procedures, instrumentation, hardware, and software used in the collection of standard National Oceanic and Atmospheric Administration (NOAA) Bathymetric Digital Elevation Models (DEMs) vary depending on systems used at the time of the survey. Log sheets were kept at all stages of processing to track file names,dates, hydrographic survey coverage, and soundings or hydrographic surveys that were deleted as part of the quality control process. A short summary of the processing steps for each estuary is available on the individual data pages. In addition, a list of each of the surveys which were included is accessible through the individual data pages. Original hydrographic data from the National Ocean Service and it predecessors was used exclusively as source data. Processing was performed on desktop computers using a variety of commercial and custom software systems. The two main software systems used were Digital Optimization of Grid Systems (DOGS) version 1.5x software developed by NOAA and MapInfo Professional version 4.5 published by MapInfo augmented by a MapInfo add-on named Vertical Mapper published by Northwood Geosciences. The processing sequence for each estuary started with the generation of a comprehensive source data set from the NOS archives, These source sounding were quality controlled to eliminate outliers and superseded surveys, optimized to reduce the number of data values, augmented with points representing the Mean High Water shoreline, and then gridded. The gridded data sets were converted from the internal proprietary grid format to Digital Elevation Model (DEM) format for public distribution. Creating Point Sets of Hydrographic Survey Data: Sounding data obtained from Hydrographic Surveys were extracted using DOGS from the GEODAS CD distributed by the National Geophysical Data Center using each estuary's shoreline as a clipping boundary. Large estuaries were broken into several overlapping regions and subsets of points were extracted and processed. Most historic hydrographic surveys are included on the GEODAS CD. For those regions which were missing data (parts of southern Florida and Chesapeake Bays only), soundings were digitized from a hard copy smooth sheets generated by the Hydrographic Surveys. Editing and Quality Control of Bathymetry Point Data: The first step of the quality control was to review the data using the DOGS software. The data were first examined for surveys or parts of surveys that are redundant. For many areas there are more surveys than are actually useful. Entire surveys or large portions of surveys were deleted for the following reasons: Another more recent survey fully covers the same area. The survey has questionable values which can not be fixed by way of figuring out a mathematical update value for the entire survey, and there are too many bad points to pick out probable "good" values. Sections of surveys were omitted if they were overlapped by more accurate surveys or by similar yet denser coverage. The second step was to display the data by depth values and to remove stray points that were obvious outliers from the surrounding data values. Optimizing the Bathymetry Point Data using DOGS: The data was first triangulated in DOGS in order to optimize the set of points. The computer program DOGS can analyze a large set of bathymetric data and create from it a smaller set of optimized points which describes the bathymetry of a geographic region to within a user defined error. This smaller data set then can be used on its own as a representation of the area's bathymetry, or as input in to other computer programs or Geographical Information Systems. There are two calculation options for triangulation in DOGS: relative and absolute. Bathymetry point files were cut into sections for separate processing based on mean depth of 10 meters. A relative height error criteria of 0.01 was used for the triangulation of regions whose depths averaged above 10 meters. An absolute height error criteria of 0.1 meters was used for areas with average depths less than 10 meters. The two resultant files were saved as text files. After combining these files, the vertical error associated with the optimized data set was 1 percent of depth or 0.1 meters, whichever was greater. The optimized DOG file was imported into MapInfo's MapInfo Professional desktop mapping software. Augmenting the data set with Shoreline Points: The final bathymetry was clipped to NOAA's 1:250,000 Coastal Assessment Framework (CAF) shoreline. A copy of the shoreline file was edited to create a point file from the vector vertices and optimized using DOGS to produce a more workable, smaller file, with little compromise to the shape of the shoreline. Mean High Water tide level was assigned to the shoreline points to give them a height. These Shoreline data points were added to the set of bathymetry points before doing the final triangulation in MapInfo. Generation of a Gridded Bathymetry Dataset: Linear triangulation of the combined point files were done in MapInfo using the Vertical Mapper 2.0 partner product software. The resultant TIN file was then used to create a continuous grid file with 30 meter resolution on a UTM projection using a NAD27 horizontal datum. A second grid was created from the first by aggregating the 30 meter grid values to 90 meter resolution and exporting the 90m center points. A new TIN was created after reattaching the shoreline pts. The triangle side lengths and coincident point distances were small enough to disallow interpolation outside the 90m distance, so as to emulate a rectangular interpolation and still allow the shoreline to be represented without averaging out the values. The result of the new file is a geographic 3 arc second resolution grid. Both grids were cut to the estuary boundary shoreline. 7.5 minute and 1 degree sections were then created from these grids. The 7.5 minute grids have 30 meter resolution in a UTM projection using the NAD27 datum. The 1 degree grids have a 3 arc second resolution in a geographic projection (Latitude/Longitude) using the NAD27 datum. In their native form, both of these grids are in proprietary formats. Creating DEM files: The MapInfo grid files were converted to a public domain USGS format DEM files using the NOAA DEM maker software. The formats available for downloading are 30 meter and 3 arc second DEMs in USGS DEM format. DEMs are viewed on interactive editing systems to identify and correct blunder and systematic errors. DEMs are verified for physical format and logical consistency.
  • 2017-04-14T00:00:00 - Original data files were converted to netCDF with GDAL transform utility.
Source Datasets
  • National Ocean Service- Hydrographic Survey Data
    • Description of Source: Source Contribution: Hydrographic Soundings; Source Type: CD-ROM
    • Temporal extent used: 1934-01-01 to 1975-01-01
  • Medium Resolution Vector Shoreline
    • Description of Source: Source Contribution: Shoreline position; Source Type: CD-ROM
    • Temporal extent used: 1970-01-01 to 1990-01-01
  • Project control
    • Description of Source: Source Contribution: Ground control points; Source Type: magnetic tape
Last Modified: 2018-06-13
For questions about the information on this page, please email: dem.info@noaa.gov