DIGITAL ELEVATION MODEL OF CAPE HATTERAS, NORTH CAROLINA

noaa / NATIONAL OCEANIC AND

ATMOSPHERIC ADMINISTRATION

National Environmental Satellite,

Data, and Information Service

NOAA Technical Memorandum NESDIS NGDC-2

DIGITAL ELEVATION MODEL OF CAPE HATTERAS, NORTH CAROLINA:

PROCEDURES, DATA SOURCES AND ANALYSIS 

L.A.Taylor

B.W. Eakins

K.S. Carignan

R.R. Warnken

D.C. Schoolcraft

G.F. Sharman

National Geophysical Data Center

Marine Geology and Geophysics Division

Boulder, Colorado

January 2008


DIGITAL ELEVATION MODEL OF CAPE HATTERAS, NORTH CAROLINA

UNITED STATES

DEPARTMENT OF COMMERCE

Carlos M. Gutierrez

Secretary

NATIONAL OCEANIC AND

ATMOSPHERIC ADMINISTRATION

VADM Conrad C. Lautenbacher, Jr.

Under Secretary for Oceans

and Atmosphere/Administrator

National Environmental Satellite,

Data, and Information Service

Mary E. Kicza

Assistant Administrator

NOAA Technical Memorandum NESDIS NGDC-2

DIGITAL ELEVATION MODEL OF CAPE HATTERAS, NORTH CAROLINA:

PROCEDURES, DATA SOURCES AND ANALYSIS

Lisa .A. Taylor1

Barry .W. Eakins2

Kelly .S. Carignan2

Robin .R. Warnken1

David C. Schoolcraft1

George F. Sharman1

1NOAA, National Geophysical Data Center, Boulder, Colorado

2Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder 

National Geophysical Data Center

Marine Geology and Geophysics Division 

Boulder, Colorado

January 2008
ii

Taylor et al., 2008

NOTICE

Menton of a commercal company or product does not consttute an endorsement by the 

NOAA Natonal Envronmental Satellte, Data, and Informaton Servce. Use of nformaton 

from ths publcaton concernng propretary products or the test of such products for publcty

or advertsng purposes s not authorzed. 

Corresponding author contact:

Lsa A. Taylor

NOAA, Natonal Geophyscal Data Center

Marne Geology and Geophyscs Dvson

35 Broadway, E/GC 3

Boulder, Colorado 80305

Phone: 303-497-6767

Fax: 303-497-653

E-mal: Lsa.A.Taylor@noaa.gov

http://www.ngdc.noaa.gov/mgg/nundaton/

Also avalable from the Natonal Techncal Informaton Servce (NTIS)

(http://www.nts.gov)
iii

DIGITAL ELEVATION MODEL OF CAPE HATTERAS, NORTH CAROLINA

Contents

1. Introduction........................................................................................................................................1

2. Study Area..........................................................................................................................................2

3. Methodology ......................................................................................................................................2

3.1 Data Sources and Processing ......................................................................................................2

3.1.1 Shoreline................................................................................................................3

3.1.2 Bathymetry ............................................................................................................4

3.1.3 Topography............................................................................................................9

3.1.4 Topography/Bathymetry......................................................................................10

3.2 Establishing Common Datums .................................................................................................11

3.2.1 Vertical transformations ......................................................................................11

3.2.2 Horizontal transformations..................................................................................12

3.3 Digital Elevation Model Development .....................................................................................13

3.3.1 Verifying consistency between datasets..............................................................13

3.3.2 Gridding the data with GMT...............................................................................13

3.4 Quality Assessment of the Grids...............................................................................................13

3.4.1 Horizontal accuracy.............................................................................................13

3.4.2 Vertical accuracy .................................................................................................13

3.4.3 Comparison with North Carolina NOAA tidal bench marks ..............................13

3.4.4 Comparison with North Carolina USGS bench marks........................................14

3.4.5 Slope map and 3-D perspectives.........................................................................15

4. Summary and Conclusions...............................................................................................................17

5. Acknowledgments............................................................................................................................17

6. References........................................................................................................................................17

List of Figures

Figure 1. Shaded-relief image, derived from the DEM, of the Cape Hatteras, North Carolina area .........1

Figure 2. Coverage of data sources used to compile the Cape Hatteras, North Carolina DEM ................2

Figure 3. NGA coastline in the area of Cape Hatteras ...............................................................................3

Figure 4. Digital NOS hydrographic survey coverage in gridding area.....................................................5

Figure 5. Spatial coverage of OCS electronic nautical charts in gridding area..........................................7

Figure 6. Spatial coverage of CCOM/JHC multibeam surveys along the U.S. Atlantic margin................8

Figure 7. Topographic LiDAR coverage tiles in the Cape Hatteras region................................................9

Figure 8. JALBTCX topographic/bathymetric LiDAR coverage in the Cape Hatteras region ...............10

Figure 9. Three VDatum regions for coastal North Carolina...................................................................11

Figure 10. VDatum model software Java input window............................................................................12

Figure 11. Slope map of the 1/3 arc-second Cape Hatteras DEM .............................................................15

Figure 12. Perspective view from the southwest of part of the Cape Hatteras DEM ................................16

Figure 13. Prominent manmade features visible in topographic LiDAR...................................................16

List of Tables

Table 1. PMEL specifications for the Cape Hatteras, North Carolina DEM ............................................2

Table 2. Bathymetric data sources used in gridding .................................................................................4

Table 3. Digital NOS hydrographic surveys included in compilation of the Cape Hatteras DEM ..........6

Table 4. Topographic data sources used in gridding.................................................................................9

Table 5. Topographic/bathymetric data source used in gridding ............................................................10

Table 6. Relationship between MHW and other vertical datums in the Cape Hatteras region...............12

Table 7. Comparison of NOAA tidal benchmark elevations with the Cape Hatteras DEM...................14

Table 8. Comparison of USGS topographic quadrangle benchmark elevations with the 

Cape Hatteras DEM...........................................................................................................14
iv

Taylor et al., 2008

[Page left intentionally blank]


DIGITAL ELEVATION MODEL OF CAPE HATTERAS, NORTH CAROLINA

Digital Elevation Model of Cape Hatteras, North Carolina:

Procedures, Data Sources and Analysis

1. Introduction

In July 2006, the National Geophysical Data Center (NGDC), an office of the National Oceanic and 

Atmospheric Administration (NOAA), developed a bathymetric/topographic digital elevation model (DEM) of Cape 

Hatteras, North Carolina (Fig. 1) for the Pacific Marine Environmental Laboratory (PMEL), NOAA Center for Tsunami 

Research (http://nctr.pmel.noaa.gov/). A 1/3 arc-second (~10 meter) elevation grid was generated from numerous, 

diverse digital datasets in the region (grid boundary and sources shown in Fig. 2). The grid will be used as input for the 

Method of Splitting Tsunami (MOST) Model (http://www.pmel.noaa.gov/pubs/PDF/tito1927/tito1927.pdf) developed 

by PMEL to simulate tsunami generation, propagation and inundation. An intermediate 9 arc-second bathymetric grid 

of the East Coast previously developed by NGDC, will also be used as input to the MOST Model. This report provides 

a summary of the data sources and methodology used in developing the Cape Hatteras DEM. 

Figure 1. Shaded-relief image, derived from the DEM, of the Cape Hatteras, North Carolina area. Red triangles locate 

tidal bench marks listed in Table 7; green stars locate USGS bench marks listed in Table 8. Contour interval (referenced to 

MHW): 5 meters subaerial, 500 meters submarine.


Taylor et al., 2008

2. Study Area

The study area covers the coastal community of Cape Hatteras, North Carolina, located on Hatteras Island, 

a low, sandy, barrier bar between the Atlantic Ocean and Pamlico Sound. The Cape Hatteras National Seashore spans 

30,319 acres, and includes Hatteras, Bodie, and Ocracoke islands. It is one of the largest stretches of undeveloped 

seashore on the U.S. Atlantic coast. Diamond Shoals, on the seaward side of Cape Hatteras, is referred to as the 

‘Graveyard of the Atlantic’, as the cape experiences frequent storms that drive ships landward toward dangerous 

shallow depths. National Ocean Service (NOS) nautical charts designate this area as hazardous to all watercraft and 

therefore is not thoroughly surveyed. Cape Hatteras Lighthouse, built in 1870, was removed in 1936 due to heavy 

beach erosion. A new lighthouse structure stands farther inland. 

3. Methodology

The Cape Hatteras DEM was developed to meet PMEL required specifications (Table 1), based on input 

requirements for the MOST inundation model. The best available data were obtained by NGDC and used to produce 

the grid. Data processing, grid assembly, and quality assessment are described in the following subsections.

Table 1: PMEL specifications for the Cape Hatteras, North Carolina grid.

Grid Area Cape Hatteras, North Carolina

Coverage Area 75.05o to 76.05o W; 34.75o to 35.80o N

Coordinate System Geographic decimal degrees

Horizontal Datum World Geodetic System (WGS84)

Vertical Datum Mean High Water

Vertical Units Meters

Grid Spacing 1/3 arc-seconds

Grid Format ASCII raster grid

3.1 Data Sources and Processing

Shoreline, bathymetric, and topographic data (Fig. 2) were obtained from numerous federal and state 

government agencies, and universities, including: the NOAA National Ocean Service (NOS) and Office of Coast 

Survey (OCS); the U.S. Army Corps of Engineers (USACE); the University of New Hampshire’s Center for Coastal 

and Ocean Mapping/Joint Hydrographic Center (CCOM/JHC); and the North Carolina Division of Emergency 

Management, Floodplain Mapping Program (NCDEM-FPMP). ESRI ArcGIS v. 9.1 (http://www.esri.com/) was used 

to display and assess data quality. Datasets were converted into ESRI shape files and transformed to Mean High Water 

(MHW) and WGS84 geographic coordinates. Vertical datum transformations were largely achieved using VDatum

model software (http://chartmaker.ncd.noaa.gov/csdl/vdatum.htm) developed jointly by OCS and NOAA’s National 

Geodetic Survey. 

Figure 2. Coverage of data sources used to compile the Cape Hatteras, North Carolina DEM.
DIGITAL ELEVATION MODEL OF CAPE HATTERAS, NORTH CAROLINA

3.1.1 Shoreline

The National Geospatial-Intelligence Agency (NGA) ‘Global Shoreline Data’ digital shoreline was used for 

evaluating the North Carolina Floodplain Mapping topographic LiDAR data (see Section 3.1.3). The NGA Global 

Shoreline Data is an unclassified vector dataset generated by Earth Satellite Corporation (http://www.earthsat.com/) of 

Rockville, Maryland for NGA, under contract to Boeing in 2004. The shoreline is referenced to MHW and constructed 

from consistently orthorectified Landsat TM satellite imagery (GeoCover Ortho), acquired between 1998-2002 for 

NASA under the Global Land Mapping Program (GLMP). NDVI and SWIR models were used to define the landward 

extent of inundation (i.e., MHW). Independently verified positional accuracy for the source product (GeoCover Ortho) 

is consistently better than 50 meter root mean square (RMS) error. The NGA coastline does not match the topographic 

LiDAR data along the open ocean–land boundary due primarily to its lower resolution (e.g., Fig. 3). Nor does it match 

satellite imagery viewable with Google Earth (http://earth.google.com/). It does, however, provide a useful check of 

the LiDAR data, but was not used in compiling the Cape Hatteras DEM.

Figure 3. NGA coastline in the area of Cape Hatteras. Left panel illustrates the mismatch between the NGA MHW 

coastline (black line) and topographic LiDAR, which is of higher resolution (blue colors are values below MHW). A 

Google Earth view of same area (right) more closely matches the LiDAR data.
Taylor et al., 2008

3.1.2 Bathymetry

Bathymetric datasets used in the compilation of the Cape Hatteras DEM include 46 NOS hydrographic 

surveys, three OCS electronic nautical charts, and deep-water multibeam surveys of the U.S. Atlantic margin conducted 

by CCOM/JHC.

Table 2. Bathymetric data sources used in gridding.

Source Year Data Type Spatial Resolution

Original Horizontal 

Datum/Coordinate 

System

Original 

Vertical 

Datum

URL

NOS 1850 to 

2001

Hydrographic 

survey 

soundings

Ranges from 10 meters to 1

kilometer (varies with scale 

of survey, depth, traffic and 

probability of obstructions)

NAD27, NAD1913, 

NAD83 

MLLW, 

MLW, 

LLW

http://www.ngdc.

noaa.gov/mgg/

bathymetry/hydro.

html

OCS 2006 Soundings from 

nautical charts 200 meters to 5 kilometers WGS84 MLLW http://chartmaker.ncd.

noaa.gov/

CCOM/JHC 2004 Multibeam 

bathymetry grid 100-meter grid spacing WGS84, geographic coordinates MSL http://ccom.unh.edu/

1) NOS hydrographic survey data

A total of 46 NOS hydrographic surveys conducted between 1870 and 2001 were included in the grid 

compilation (Fig. 4). The survey data were originally vertically referenced to either Mean Lower Low Water 

(MLLW), Mean Low Water (MLW) or Local Low Water (LLW), and horizontally referenced to either 

NAD1913, NAD27 or NAD83 (Table 3). Data point spacing for the surveys ranged from about 10 meters in 

shallow water to 1 kilometer in deep water. All surveys were extracted from NGDC’s online database (http://

www.ngdc.noaa.gov/mgg/bathymetry/hydro.html) in NAD83 and MLLW, MLW and LLW datums. The data 

were then converted to WGS84 using FME software, an integrated collection of spatial extract, transform, 

and load tools for data transformation (http://www.safe.com). The surveys were subsequently clipped to a 

polygon 5% larger than the final gridding area to support data interpolation along grid edges. 

After converting all NOS survey data to MHW (see Section 3.2.1), the data were displayed in ESRI 

ArcMap and reviewed for digitizing errors against scanned original survey smooth sheets and compared to 

current topographic LiDAR data, the NGA coastline, and Google Earth satellite imagery. Geomorphologic 

and anthropogenic modification of the barrier-bar coastline has resulted in inconsistencies between the NOS 

survey data and recent topographic LiDAR data, necessitating modification of the NOS bathymetric data—

this is especially true for the oldest NOS surveys. 

13 NOS surveys were not available in digital format, resulting in some bathymetric coverage gaps (see 

Fig. 2 and 4), which were filled with OCS electronic nautical charts.
DIGITAL ELEVATION MODEL OF CAPE HATTERAS, NORTH CAROLINA

Figure 4. Digital NOS hydrographic survey coverage in the Cape Hatteras region. Red line denotes 

DEM boundary; NGA coastline in black.
Taylor et al., 2008

Table 3. Digital NOS hydrographic surveys included in the Cape Hatteras, North Carolina DEM.

Survey ID Year Survey Scale Original Horizontal 

Datum Original Vertical Datum VDatum Transform Tool+

F00462 2000 10,000 NAD83 MLLW central

H01083 1870 40,000 undetermined - NAD27 MLW pamlico

H01226B 1874 20,000 NAD1913 Local LW FME

H01227 1874 40,000 undetermined Local LW FME

H01254 1875 20,000 undetermined Local LW FME

H01867 1887 20,000 undetermined MLW pamlico

H03902 1916 20,000 NAD1913 Local LW FME

H03922 1916 20,000 NAD1913 Local LW FME

H04012 1917 40,000 NAD1913 Local LW FME

H04013 1917 20,000 NAD1913 Local LW FME

H04734 1927 20,000 NAD1913 MLW pamlico/central

H04778 1927 20,000 NAD1913 Local LW FME

H05814 1935 10,000 NAD27 MLW pamlico/central

H05913 1935 20,000 NAD27 MLW FME 

H05914 1935 10,000 NAD27 MLW FME 

H05915 1935 10,000 NAD27 Local LW FME 

H06228 1937 10,000 NAD27 MLW pamlico/north

H06834 1943 10,000 NAD27 MLW pamlico/central

H06835 1943 20,000 NAD27 MLW pamlico

H06836 1943 10,000 NAD27 MLW pamlico

H08249 1955 20,000 NAD27 MLW central

H08291 1956 10,000 NAD27 MLW pamlico/central

H08766 1962 10,000 NAD27 MLW pamlico/central

H08808 1964 20,000 NAD27 MLW central

H08809 1964 20,000 NAD27 MLW north/central

H08810 1965 40,000 NAD27 MLW north/central

H09060 1970 80,000 NAD27 MLW central

H09104 1970 80,000 NAD27 MLW central

H09137 1970 40,000 NAD27 MLW north

H09155 1970 40,000 NAD27 MLW north 

H09231 1971 80,000 NAD27 MLW north/central

H09243 1971 80,000 NAD27 MLW north

H09450 1974 40,000 NAD27 MLW central

H09451 1974 40,000 NAD27 MLW central

H09525 1975 10,000 NAD27 MLW north

H09526 1975 5,000 NAD27 MLW pamlico

H09527 1975 5,000 NAD27 MLW pamlico/north

H09528 1975 5,000 NAD27 MLW pamlico

H09529 1975 5,000 NAD27 MLW pamlico/north

H09530 1975 5,000 NAD27 MLW north

H09733 1977/78 20,000 NAD27 Low water (.5 ft. below 

Mean Water Level FME

H09748 1978 20,000 NAD27 Local LW FME

H09802 1978/79 20,000 NAD27 Local LW FME

H09821 1979/80 20,000 NAD27 Local LW FME

H09863 1980 20,000 NAD27 Low water (.5 ft. below 

Mean Water Level FME

H10872 2001 10,000 NAD83 MLLW pamlico/central

+

 ‘FME’ transformations using -0.15 meter vertical shift—Local Low Water to MHW in Pamlico Sound.
DIGITAL ELEVATION MODEL OF CAPE HATTERAS, NORTH CAROLINA

2) OCS electronic nautical charts

Three electronic nautical charts in the Cape Hatteras region (#11520, #11555, and #12205; Fig. 5) were 

downloaded from NOAA’s Office of Coast Survey (OSC) website (http://chartmaker.ncd.noaa.gov/). Chart 

sounding data were originally in WGS84 geographic and MLLW (units of meters) datums. Chart #12205, 

in Albemarle Sound, has point spacings between roughly 200 meters and one kilometer in the vicinity of 

Oregon Inlet, a region without digital NOS hydrographic survey data. Chart #11555, Pamlico Sound, also 

has point spacings between 200 meters and one kilometer, while Chart #11520, deep-water soundings from 

Cape Hatteras to Charleston, has point spacings between 2 and 5 kilometers. Though the soundings on these 

three nautical charts are sparse, they provided the only digital values in some areas (see Fig. 2). Soundings 

were clipped to a polygon 5% larger than the gridding area, converted to MHW, then used in the gridding 

process.

Figure 5. Spatial coverage of OCS electronic nautical charts in gridding area.
Taylor et al., 2008

3) Gridded multibeam bathymetric surveys

The University of New Hampshire’s Center for Coastal and Ocean Mapping/Joint Hydrographic Center 

(CCOM/JHC; http://ccom.unh.edu/) has conducted deep-water multibeam sonar surveys of the U.S. Atlantic 

margin in support of the United Nations Convention on the Law of the Sea (Gardner, 2004). A small portion 

of one CCOM/JHC gridding region (“South”, Fig. 6) overlaps the southeastern corner of the Cape Hatteras 

gridding region (see Fig. 2). Data from this 100-meter grid was extracted, clipped to a polygon 5% larger than 

the Cape Hatteras gridding region, converted to MHW and then used in the gridding process.

Figure 6. Spatial coverage of CCOM/JHC multibeam surveys along the U.S. Atlantic margin.
DIGITAL ELEVATION MODEL OF CAPE HATTERAS, NORTH CAROLINA

3.1.3 Topography

High-resolution topographic LiDAR data collected and processed in 2001 by the North Carolina Division 

of Emergency Management, Floodplain Mapping Program (NCDEM-FPMP) were used for subaerial regions in the 

compilation of the grid (Fig. 6). The NCDEM-FPMP was established in response to the extensive damage caused by 

Hurricane Floyd in 1999, and these data were collected as part of its effort to modernize FEMA Flood Insurance Rate 

Maps (FIRM) statewide. The data were received in ASCII xyz format organized in 10,000 ft x 10,000 ft tiles using 

the North Carolina Bureau of Land Records Management standards. The data were collected at 5-meter nominal post 

spacing and referenced to NAD83 North Carolina State Plane and NAVD88 horizontal and vertical datums, units of 

feet.

Although not used in the compilation of the Cape Hatteras DEM, ultra-high-resolution topographic LiDAR 

data (1/3 meter postings) were collected along the North Carolina coastline by the Joint Airborne Lidar Bathymetry 

Technical Center of Expertise (JALBTCX; http://shoals.sam.usace.army.mil/) following the 2004 hurricane season, and 

provided to NGDC. The NCDEM-FPMP topographic data matched well with this very dense JALBTCX topographic 

data, and was of sufficient density as to make the JALBTCX data redundant; the NCDEM-FPMP data also provided 

complete coverage of subaerial regions within the Cape Hatteras gridding region.

Table 4. Topographic data sources used in gridding.

Source Year Data Type Spatial Resolution

Original Horizontal 

Datum/Coordinate 

System

Original 

Vertical 

Datum

URL

NCDEMFPMP 2001 Topographic 

LiDAR

5-meter nominal post 

spacing

NAD83, North 

Carolina State Plane 

(feet) 

NAVD88

(feet)

http://www.

ncfloodmaps.com/

Figure 7. Topographic LiDAR coverage tiles in the Cape Hatteras region. Red line denotes DEM 

boundary; NGA coastline in gray.
10

Taylor et al., 2008

3.1.4 Topography/Bathymetry

High-resolution combined topographic/bathymetric LiDAR surveys of the North Carolina open-ocean 

coastline were conducted by Joint Airborne Lidar Bathymetry Technical Center of Expertise (JALBTCX; http://

shoals.sam.usace.army.mil/), providing a dense dataset in the shallowest bathymetric zone. JALBTCX performs 

operations, research, and development in airborne LiDAR bathymetry and complementary technologies to support the 

coastal mapping and charting requirements of the U.S. Army Corps of Engineers (USACE) National Coastal Mapping 

Program, the U.S. Naval Meteorology and Oceanography Command, and NOAA.

The JALBTCX LiDAR data used in gridding was collected in 2004 along the North Carolina coast using the 

Compact Hydrographic Airborne Rapid Total Survey (CHARTS) system. The CHARTS system includes an Optech, 

Inc., SHOALS-3000 LiDAR instrument integrated with an Itres CASI-1500 hyperspectral imager and collects either 20 

kHz topographic LiDAR data or 3 kHz bathymetric LiDAR data, each concurrent with digital RGB and hyperspectral 

imagery.

Bathymetric data were collected from the shoreline to ~1 km offshore at 5-meter spacing; topographic data 

were collected from the shoreline to 0.5 km onshore at 1-meter spacing. The topographic data were collected in 

opposing flight directions, resulting in 200% coverage of the land portion of the survey. All data were positioned using 

post-processed kinematic GPS and National Geodetic Survey monumentation.

The bathymetric data from the JALBTCX combined topographic/bathymetric LiDAR surveys were of 

significantly higher resolution than the sparser NOS hydrographic surveys—they were also consistent with those 

NOS soundings. The topographic data, however, did not overlap well with the subaerially complete NCDEM-FHMP 

topographic data or with the 1/3-meter postings from the entirely topographic surveys performed by JALBTCX (see 

Section 3.1.3): shifting topographic features horizontally by tens of meters in some cases. Thus, NGDC chose to use 

only the bathymetric data from the JALBTCX combined topographic/bathymetric surveys.

Table 5. Topographic/ Bathymetric LiDAR data source used in gridding.

Source Year Data Type Spatial Resolution

Original Horizontal 

Datum/Coordinate 

System

Original 

Vertical 

Datum

URL

JALBTCX 2004

Topographic/

bathymetric 

LiDAR

0.5 to 5 meter point 

spacing

NAD83, geographic 

coordinates

NAVD88 http://www.sac.

usace.army.mil/

Figure 8. JALBTCX topographic/bathymetric LiDAR coverage in the Cape Hatteras region. Red line 

denotes DEM boundary; NGA coastline in gray.
11

DIGITAL ELEVATION MODEL OF CAPE HATTERAS, NORTH CAROLINA

3.2 Establishing Common Datums

3.2.1 Vertical datum transformations

Datasets used in the compilation of the Cape Hatteras DEM were originally referenced to a number of 

vertical datums including: Mean Low Water (MLW), Local Low Water (LLW), Mean Lower Low Water (MLLW), 

and North American Vertical Datum of 1988 (NAVD88). All datasets were transformed to MHW to provide the worst 

case scenario for inundation modeling. 

1) Bathymetric data

The OCS electronic nautical charts and most of the NOS surveys were transformed to MHW using 

VDatum (http://nauticalcharts.noaa.gov/csdl/vdatum.htm) model software developed jointly by OSC and 

NOAA’s National Geodetic Survey. For the Cape Hatteras gridding area, the VDatum Transformation Tool 

consists of three Java based programs applicable to three specific North Carolina coastal regions (Fig. 8). 

Figure 9. Three VDatum regions for coastal North Carolina.

NOS surveys were grouped by reference to original vertical datum (see Table 3) and input to VDatum 

using the batch mode utility (Fig. 9). Surveys that spanned two VDatum regions were input to both transform 

tools, which only transform soundings within the specified region. Some surveys in Pamlico Sound were 

originally referenced to LLW, a vertical datum not supported by VDatum. These survey depths were brought 

to MHW by adding a constant of -0.15 meters (Dr. Kurt Hess, NOAA Office of Coastal Survey, Kurt.Hess@

noaa.gov, personal communication).
12

Taylor et al., 2008

Figure 10. VDatum model software Java input window.

Other bathymetric datasets, in Mean Sea Level (MSL) vertical datum, were converted to MHW using 

FME software by adding a constant offset of -0.179 (Table 6), which was derived by averaging the difference 

between MSL and MHW at tidal stations along the Cape Hatteras coastline (http://tidesandcurrents.noaa.

gov/).

2) Topographic and topographic/bathymetric LiDAR data

Topographic and topographic/bathymetric LiDAR data were converted from NAVD88 to MHW using 

FME software by adding a constant value of -0.126 meters (Table 6).

Table 6. Relationship between Mean High Water and other vertical datums in the Cape Hatteras region.*

Vertical datum Difference to MHW

NAVD88 -0.126

MSL -0.179

MLW -0.405

NGVD29 -0.449

LLW -0.15

* Datum relationships derived from averaging tidal range values at up to 7 tidal stations within the Cape Hatteras 

region—vertical datums are not necessarily benchmarked at all stations.

3.2.2 Horizontal datum transformations

Datasets used to compile the grid were originally horizontally referenced to NAD83, WGS84, NAD27, or 

North Carolina State Plane horizontal datums; the relationships and transformational equations between these horizontal 

datums are well established. All data were converted to a horizontal datum of WGS84 using FME software. 
13

DIGITAL ELEVATION MODEL OF CAPE HATTERAS, NORTH CAROLINA

3.3 Digital Elevation Model Development

3.3.1 Verifying consistency between datasets

After horizontal and vertical transformations were applied, the resulting ESRI shape files were checked in 

ESRI ArcMap for inter-dataset consistency. Problems and errors were identified and resolved before proceeding with 

subsequent gridding steps; the quality-assessed ESRI shape files were then converted to xyz files in preparation for 

gridding. Problems included:

•	 Mismatch between the topographic data of the combined topographic/bathymetric LiDAR surveys conducted 

by JALBTCX with the exclusively topographic LiDAR surveys conducted by JALBTCX and NCDEMFPMP. The topographic part of the JALBTCX combined LiDAR surveys was excluded from the gridding 

process.

3.3.2 Gridding the data with GMT

As there was very little overlap between the various data sets—with the exception of the NOS surveys and 

OCS chart soundings, which were highly consistent—all processed xyz files were gridded with GMT (http://gmt.

soest.hawaii.edu/). GMT is an NSF-funded share-ware software application designed to manipulate data for mapping 

purposes. The GMT tool ‘surface’ was used to create the 1/3 arc-second Cape Hatteras grid—a modeled surface 

draping the point data—of combined sounding and topographic point data. These point data were first combined 

into an individual file, then smoothed using the GMT tool ‘blockmedian’ onto a 1/3 arc-second grid 5% larger than 

the gridding region. ‘Surface’ then applied a tight spline tension to interpolate cells without data values; ‘surface’ 

does not support a data hierarchy. The GMT grid created by ‘surface’ was converted into an Arc ASCII file using the 

MB-System tool ‘mbm_grd2arc’; MB-System is also an NSF-funded share-ware application that has numerous data 

processing and conversion tools (http://www.ldeo.columbia.edu/res/pi/MB-System/).

3.4 Quality Assessment of the Grids.

3.4.1. Horizontal accuracy

The digital elevation grids have an estimated horizontal accuracy of about 10 meters for topographic features; 

the LiDAR data has an accuracy of ~2 meters for individual postings. Bathymetric features are resolved only to 

within a few hundred meters in deep water areas; shallow, near-coastal regions have an accuracy approaching the 

subaerial topographic features. Positional accuracy is limited by: transformation of multiple datasets from various 

datums; sparseness of deep-water soundings; potentially large positional accuracy of pre-satellite navigated (GPS) 

hydrographic surveys; and natural and artificial morphologic change that has occurred since the hydrographic surveys 

were conducted.

3.4.2 Vertical accuracy

The grids have an estimated vertical accuracy of 0.1 to 1 meters for topographic areas and 0.1 meters to 5% 

of water depth for bathymetric areas. Topographic values are derived from NCDEM-FPMP and JALBTCX LiDAR 

surveys, which have an estimated vertical accuracy of 0.1 to 0.15 meters. Bathymetric values were derived from the 

wide range of input data single and multibeam sounding measurements from the late 19th and early 20th centuries 

to recent. Gridding interpolation to determine values between sparse, poorly located NOS soundings degrades the 

vertical accuracy of elevations in deep water. 

3.4.3 Comparison with North Carolina NOAA tidal bench marks

Four tidal bench marks within the Cape Hatteras study area were compared with values taken at the same 

locales from the 1/3 arc-second (~10 meter) DEM (see Fig. 1 and Table 7 for station locations). Each bench mark has 

a geographic position recorded to within 1 arc-second, with an accuracy of +/-6 arc-seconds (http://tidesandcurrents.

noaa.gov/). Most bench marks are level with the ground surface; the rest are within a few centimeters. The National 

Geodetic Survey (NGS) data sheets for the tidal stations also document benchmark elevation above MHW, in meters, 

allowing for direct comparison with grid values at those locations. Most grid values compare favorably with the 
14

Taylor et al., 2008

known bench mark elevations. The Oregon Inlet bench mark has the largest discrepancy, 2.6 m, which is due partly to 

its being located at the north end of Bonner Bridge, elevated 0.3 m above the highway. 

Table 7. Comparison of NOAA tidal benchmark elevations, in meters above MHW, with the Cape Hatteras DEM.

STATION

NUMBER

STATION

NAME YEAR LONGITUDE LATITUDE BENCH MARK

GRID 

VALUE DIFFERENCE

8654400 CAPE HATTERAS 

FISHING PIER 1980 075°38’23”W 35°13’37”N 0.231 0.616 -0.385

8652587 OREGON INLET 1974 075°32’49”W 35°47’40”N 4.100 1.473 2.627

8652587 USCG LIFEBOAT 

STATION 1974 075°31’25”W 35°46’04”N 1.259 1.539 -0.280

8653215 RODANTHE, 

PAMLICO SOUND 1977 075°28’07”W 35°35’35”N 1.072 0.710 0.362

Standard Deviation: 1.403

3.4.4 Comparison with North Carolina USGS bench marks

Benchmark elevations were extracted from online digital USGS topographic quadrangles (http://www.

topozone.com), which give benchmark position and elevation in WGS84 and NVGD29 vertical datum (in feet). 

Elevations were converted to meters and shifted to MHW vertical datum (see Table 6) for comparison with the Cape 

Hatteras DEM. The four USGS bench marks with discrepancies greater than 2 m are all located along the open-ocean 

edge of Hatteras Island. In each case, the grid value for the location of the corresponding bench mark accurately 

reflects the values of the surrounding NCDEM-FPMP topographic LiDAR data. The origin of the mismatch between 

the topographic LiDAR data and the USGS benchmark elevations is unknown.

Table 8. Comparison of USGS topographic quadrangle benchmark elevations, in meters above MHW, with the Cape Hatteras 

DEM.

LONGITUDE LATITUDE BENCH MARK GRID VALUE DIFFERENCE

-75.9882 35.1069 0.16 0.78 -0.62

-75.6974 35.2161 0.16 0.17 0.00

-75.9045 35.6411 0.16 0.35 -0.19

-75.5462 35.2683 0.47 0.46 0.01

-75.9217 35.6293 0.47 0.37 0.10

-75.7795 35.693 0.47 0.93 -0.46

-75.7731 35.6965 0.47 0.16 0.31

-75.9211 35.633 0.78 0.15 0.63

-75.7885 35.808 0.78 0.41 0.37

-75.8061 35.8273 0.78 0.37 0.41

-75.8749 35.1461 1.09 1.31 -0.22

-75.4672 35.5955 1.09 1.24 -0.16

-75.8547 35.6313 1.09 0.65 0.43

-75.8903 35.6459 1.09 0.44 0.64

-75.7683 35.7215 1.09 0.32 0.76

-75.7685 35.736 1.09 0.60 0.49

-75.769 35.7694 1.09 1.09 -0.01

-75.7767 35.7951 1.09 0.53 0.56

-75.7952 35.8152 1.09 0.55 0.53

-75.7203 35.2 1.39 0.74 0.65

-75.6758 35.2147 1.39 1.04 0.35

-75.6625 35.2183 1.39 1.79 -0.40

-75.4872 35.4187 1.39 1.51 -0.12

-75.7807 35.6328 1.39 0.86 0.54

-75.7773 35.6513 1.39 1.07 0.32

-75.78 35.6802 1.39 1.57 -0.18

-75.7694 35.7835 1.39 0.27 1.12

-75.6121 35.2316 1.70 5.24 -3.54

-75.4771 35.5064 1.70 1.40 0.30

-75.4766 35.6651 1.70 2.95 -1.25

-75.7749 35.6966 1.70 0.47 1.23

-75.5212 35.7701 1.70 0.20 1.50

-75.7037 35.2055 2.01 2.30 -0.29
15

DIGITAL ELEVATION MODEL OF CAPE HATTERAS, NORTH CAROLINA

-75.5212 35.2555 2.01 1.79 0.21

-75.6541 35.2206 2.31 -0.15 2.46

-75.5211 35.2533 2.31 -0.26 2.57

-75.6624 35.2183 2.62 1.79 0.83

-75.5951 35.235 2.62 2.36 0.26

-75.5511 35.238 2.62 1.65 0.97

-75.471 35.5265 2.62 4.91 -2.30

-75.7873 35.6215 1.39 0.48 0.91

Standard Deviation: 1.54

3.4.5 Slope map and 3-D perspectives

ESRI ArcCatalog was used to generate a slope map from the Cape Hatteras DEM to allow for visual inspection 

and identification of artificial slopes along boundaries between datasets (Fig. 11). The grid was transformed to UTM 

Zone 18 coordinates (horizontal units in meters) in ArcCatalog for derivation of the slope grid; equivalent horizontal 

and vertical units are required for effective slope-map derivation. Analysis of preliminary slope maps revealed suspect 

data points, which were corrected before regridding the data. Three-dimensional viewing of the UTM-transformed 

grid (e.g., Fig. 12) was accomplished using ESRI ArcScene. The sparseness of the OCS electronic nautical chart data 

in the southeast (deep-water) corner of the DEM created smooth “tent poles” that are apparent in the southeast corner 

of Figure 11; these artifacts could not be excised from the DEM.

Figure 11. Slope map of the 1/3 arc-second Cape Hatteras DEM. Flat-lying slopes are 

white; dark shading denotes steep slopes; NGA coastline in red. Prominent dark feature 

at 35°04’N, 075°43’W is from real NOS sounding on chart H09104.
16

Taylor et al., 2008

Figure 12. Perspective view from the southwest of part of the Cape Hatteras DEM. 

Diamond Shoals is a prominent shallow region extending southeast from Cape Hatteras. 

NGA coastline in red; vertical exaggeration–times 100.

A region of prominent patterned lineations in the Cape Hatteras DEM lies on the landward side of Pamlico 

Sound (see northwest corner of Fig. 1 where some land topography lies below the MHW zero level). The lineations 

are clearly resolvable within the NCDEM-FPMP topographic LiDAR data, and in Google Earth satellite imagery (Fig. 

13) and are not gridding-related artifacts. As such, they are interpreted as large-scale manmade structures, perhaps 

related to local farming endeavours.

Figure 13. Prominent manmade features visible in topographic LiDAR data. Left panel shows an example of linear 

features resolvable in a tile of the NCDEM_FPMP topographic LiDAR data; NGA coastline is in red. Right panel shows a 

Google Earth satellite image of the same region. This patchwork of lineated features is also present in the Cape Hatteras 

DEM, some of which lie below the MHW zero level. 
17

DIGITAL ELEVATION MODEL OF CAPE HATTERAS, NORTH CAROLINA

4. Summary and Conclusions

A topographic/bathymetric digital elevation model with cell spacing of 1/3 arc-second (~10 meters) of the 

Cape Hatteras, North Carolina area was developed for the Pacific Marine Environmental Laboratory (PMEL), NOAA 

Center for Tsunami Inundation Mapping Efforts (TIME). The best available data from U.S. federal and state agencies, 

and universities were obtained for grid compilation. The data were quality checked, processed and gridded using ESRI 

ArcGIS, FME, GMT and MB-System software. 

Recommendations to improve the DEMs based on NGDC’s research and analysis are listed below:

•	 Resurvey bathymetric regions without digital data, or digitize analog NOS sounding sheets for these areas.

5. Acknowledgments

The creation of these grids was funded by the NOAA, Pacific Marine Environmental Laboratory. The authors 

thank Chris Chamberlin, Angie Venturato, and Hal Mofjeld (PMEL), Adeline Wong and Steven White (NOS, Coastal 

Survey Development Lab), James Gardner and Larry Mayer (CCOM/JHC), Jeff Lillycrop (USACE), Charity Peterson 

(NCDEM-FPMP), and John Von Rosenberg (NGA).

6. References

Gardner, V. James, 2004. U.S. Law of the Sea cruise to map the foot of the slope and 2500-m isobath of the Northeast 

US Atlantic continental margin. CRUISES H04-1, 2 and 3 August 23, to November 30, 2004 Gulfport, MS to Norfolk, 

VA. University of New Hampshire, Center for Coastal and Ocean Mapping/Joint Hydrographic Center, Durham, New 

Hampshire.

Nautical Chart #11520, 36th Edition. 1996. Cape Hatteras to Charleston. Scale 1:432,720. U.S. Department of 

Commerce, NOAA, National Ocean Service, Coast Survey.

Nautical Chart #11555, 36th Edition. 1997. Cape Hatteras, Wimble Shoals to Ocracoke Inlet, North Carolina. Scale 

1:80,000. U.S. Department of Commerce, NOAA, National Ocean Service, Coast Survey.

Nautical Chart #12205, 36th Edition. 1997. Cape Henry to Pamlico Sound, including Albemarle Sound. Scale various. 

U.S. Department of Commerce, NOAA, National Ocean Service, Coast Survey.