noaa / NATIONAL OCEANIC AND

ATMOSPHERIC ADMINISTRATION

National Environmental Satellite,

Data, and Information Service

NOAA Technical Memorandum NESDIS NGDC-54

DIGITAL ELEVATION MODELS OF PALM BEACH, FLORIDA:

PROCEDURES, DATA SOURCES AND ANALYSIS 

D.Z. Friday

L.A. Taylor

B.W. Eakins

R.R. Warnken

K.S. Carignan

R.J. Caldwell 

E. Lim

P.R. Grothe

National Geophysical Data Center

Marine Geology and Geophysics Division

Boulder, Colorado

August 2012

UNITED STATES

DEPARTMENT OF COMMERCE

Rebecca Blank

Acting Secretary

NATIONAL OCEANIC AND

ATMOSPHERIC ADMINISTRATION

Dr. Jane Lubchenco

Under Secretary for Oceans

and Atmosphere/Administrator

National Environmental Satellite,

Data, and Information Service

Mary E. Kicza

Assistant Administrator

NOAA Technical Memorandum NESDIS NGDC-54

DIGITAL ELEVATION MODELS OF PALM BEACH, FLORIDA:

PROCEDURES, DATA SOURCES AND ANALYSIS 

Dorothy Z. Friday1 

Lisa A. Taylor2

Barry W. Eakins1

Robin R. Warnken2

Kelly S. Carignan1

R. Jason Caldwell1

Elliot Lim1

Pamela R. Grothe1

1Cooperative Institute for Research in Environmental Sciences, University of Colorado at Boulder 

2NOAA, National Geophysical Data Center, Boulder, Colorado 

National Geophysical Data Center

Marine Geology and Geophysics Division 

Boulder, Colorado

August 2012
Friday et al., 2012

ii

NOTICE 

Mention of a commercial company or product does not constitute an endorsement by the 

NOAA National Environmental Satellite, Data, and Information Service. Use of information 

from this publication concerning proprietary products or the test of such products for publicity 

or advertising purposes is not authorized. 

Corresponding project contact:

Lisa A. Taylor

NOAA National Geophysical Data Center

Marine Geology and Geophysics Division

325 Broadway, E/GC 3

Boulder, Colorado 80305

Phone: 303-497-6767

Fax: 303-497-6513

E-mail: Lisa.A.Taylor@noaa.gov

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

Also available from the National Technical Information Service (NTIS)

(http://www.ntis.gov)
Digital Elevation Models of Palm Beach, Florida

iii

Contents

1..Introduction 1

2..Study Area 2

3..Methodology 4

3.1 Data Sources and Processing 5

3.1.1 Shoreline 6

3.1.2 Bathymetry 7

3.1.3 Topography 16

3.2 Establishing Common Datums 18

3.2.1 Vertical datum transformations 18

3.2.2 Horizontal datum transformations 20

3.3 Digital Elevation Model Development 21

3.3.1 Verifying consistency between datasets 21

3.3.2 Smoothing of bathymetric data 21

3.3.3 Building the NAVD 88 DEM 23

3.3.4 Building the MHW DEM 23

3.4 Quality Assessment of the DEMs 26

3.4.1 Horizontal accuracy 26

3.4.2 Vertical accuracy 26

3.4.3 Slope map and 3-D perspectives 26

3.4.4 Comparison with National Geodetic Survey geodetic monuments 29

3.4.5 NAVD 88 DEM comparison with source data files 30

4..Summary and Conclusions 33

5..Acknowledgments 33

6..References 33

7..Data Processing Software 34

List of Figures

Figure 1. Shaded-relief image of the Palm Beach NAVD 88 1/3 arc-second DEM 1

Figure 2. Overview of the Palm Beach DEM region 2

Figure 3. Lake Worth Inlet and the intracoastal waterway 3

Figure 4. Aerial photograph showing sand bars of St.Lucie Inlet 3

Figure 5. Source and coverage of datasets used in compiling the Palm Beach DEMs. 5

Figure 6. Portion of lidar-derived contours, shown with extracted zero contour line 6

Figure 7. Source and coverage of bathymetric datasets used in compiling the Palm Beach DEMs 8

Figure 8. ENC coverage in the Palm Beach area 9

Figure 9. NOS hydrographic survey coverage in the Palm Beach region. 11

Figure 10. Spatial Coverage of the Palm Beach County LADS data 12

Figure 11. Spatial coverage of the SFWMD hydrographic survey in St.Lucie estuary 13

Figure 12. Comparison of original SFWMD hydrographic survey xyz points and NGDC triangulated

surface 13

Figure 13. Spatial coverage of USACE hydrographic survey data in the vicinity of Palm Beach 15

Figure 14. Source and coverage of topographic datasets used in compiling the Palm Beach DEMs 16

Figure 15. Locations of NOAA tide stations in the Palm Beach area. 19

Figure 16. Histogram of the differences between the NOS bathymetric surveys and the 1 arc-second

pre-surfaced bathymetric grid 22

Figure 17. Histogram of the differences between all original bathymetric data and the 1 arc-second

pre-surfaced bathymetric grid 22

Figure 18. Image of NGDC Palm Beach conversion grid. 24

Figure 19. Histogram of the differences between the conversion grid and xyz difference files using

NOS hydrographic survey data 25

Figure 20. Slope map of the Palm Beach NAVD 88 DEM. Flat-lying slopes are shown in white; dark.

shading denotes steep slopes; combined coastline indicated in red. 27
Friday et al., 2012

iv

List of Tables

Table 1. Specifications for the Palm Beach DEMs.................................................................................. 4

Table 2. Shoreline datasets used in developing the Palm Beach NAVD 88 DEM. 6

Table 3. Bathymetric datasets used in compiling the Palm Beach NAVD 88 DEM. 7

Table 4. Digital NOS hydrographic surveys used in developing the Palm Beach NAVD 88 DEM. 10

Table 5. USACE hydrographic surveys used in compiling the Palm Beach DEMs. 14

Table 6. Topographic datasets used in compiling the Palm Beach DEMs. 16

Table 7. Tide stations in the Palm Beach area and relationships between NGVD 29 and NAVD 88 18

Table 8. Data hierarchy used to assign gridding weight in MB-System. 23

Figure 21. Perspective view from the northeast of the 1/3 arc-second Palm Beach NAVD 88 DEM 28

Figure 22. Data contribution plot of the Palm Beach NAVD 88 DEM 28

Figure 23. Location of NGS geodetic monuments in the Palm Beach region 29

Figure 24. Histogram of the differences between NGS geodetic monument elevations and the Palm

Beach NAVD 88 DEM 29

Figure 25. Histogram of the differences between the deep water portion of the Palm Beach NOS DEM

data points and the NAVD 88 DEM. 30

Figure 26. Histogram of the differences between the shallow water portion of the Palm Beach NOS

DEM data points and the NAVD 88 DEM 31

Figure 27. Histogram of the differences between the Palm Beach USACE hydrographic survey DEM

data points and the NAVD 88 DEM 31

Figure 28. Histogram of the differences between the SFWMD hydrographic survey DEM data points

and the NAVD 88 DEM 31

Figure 29. Histogram of the differences between the Palm Beach JALBTCX lidar survey DEM data.

points and the Palm Beach NAVD 88 DEM 32

Figure 30. Histogram of the differences between the Palm Beach County LADS DEM data points and

the Palm Beach NAVD 88 DEM 32

Figure 31. Histogram of the differences between FDEM lidar surveys DEM data points and the Palm.

Beach NAVD 88 DEM 32

Figure 32. Histogram of the differences between SRTM DEM data points and the Palm Beach NAVD

88 DEM 33
Digital Elevation Models of Palm Beach, Florida:

Procedures, Data Sources and Analysis 

1. Introduction

The National Geophysical Data Center (NGDC), an office of the National Oceanic and Atmospheric Administration (NOAA), has developed two bathymetric–topographic digital elevation models (DEMs) of Palm Beach,

Florida (Fig. 1). First, a 1/3 arc-second1 DEM referenced to North American Vertical Datum of 1988 (NAVD 88) was

developed and evaluated using diverse digital datasets available for the region (grid boundary and sources shown in

Fig. 5). Then, a 1/3 arc-second conversion grid was created to represent the relationship between NAVD 88 and Mean

High Water (MHW) vertical datums in the Palm Beach region. Finally, a 1/3 arc-second MHW DEM was developed

by combining the NAVD 88 DEM and the vertical datum conversion grid. The MHW DEM will be used as input for

the Method of Splitting Tsunami (MOST) model developed by the Pacific Marine Environmental Laboratory (PMEL)

NOAA Center for Tsunami Research (HUhttp://nctr.pmel.noaa.gov/UH) to simulate tsunami generation, propagation and

inundation as part of the tsunami forecast system Short-term Inundation Forecasting for Tsunamis (SIFT) currently being developed by PMEL for the NOAA Tsunami Warning Centers. This report provides a summary of the data sources

and methodology used in developing the Palm Beach DEMs.

Figure 1. Shaded-relief image of the Palm Beach NAVD 88 1/3 arc-second DEM.

1. The Palm Beach DEMs are built upon a grid of cells that are square in geographic coordinates (latitiude and longitude), however, the cells are

not square when converted to projected coordinate systems such as UTM zones (in meters). At the latitude of Palm Beach, Florida, (26°42' 54"N,

80°02'22"W) 1/3 arc-second of latitude is equivalent to 10.26 meters; 1/3 arc-second of longitude equals 9.21 meters.

Elevation (meters)
Friday et al., 2012

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2. Study Area

The Palm Beach DEM provides coverage of the area surrounding Palm Beach, Florida– from St.Lucie Inlet

to Boca Raton (Fig. 2). The town of Palm Beach is located approximately 70 miles north of Miami and 150 miles

south of Cape Canaveral. The town was founded in the early twentieth century as a resort destination, and its population remains mostly seasonal. The town has 10,000 year-round residents, with a seasonal population of about 30,000.

The town of Palm Beach is located on a barrier island, and is separated from the remainder of Palm Beach

County by the Intracoastal Waterway (Fig. 3). Dredging work along the intracoastal waterway is performed frequently. In addition, many other man-made projects occur along the coast, including the construction of walled canals and

yacht slips, golf course terrain creation projects, and beach restoration and sediment pumping operations.

Elevation modeling in the Palm Beach region is complicated by sand transport issues. The sand dunes and

sand bars in the area (Fig. 4) are fragile and constantly migrate. Small disruptions to the environment, both natural

and man-made, lead to rapid geomorphological changes along canals, rivers, islands, inlets, and coastal dunes in the

area. The Palm Beach DEMs are representative of the basic terrain, but constant alterations to the landscape make it

difficult to acquire and create coastal elevation data sets that will remain accurate throughout time.

Figure 2. Overview of the Palm Beach DEM region. Blue box represents Palm Beach DEM extents. 
Digital Elevation Models of Palm Beach, Florida

3

Figure 3. Lake Worth Inlet and the intracoastal waterway. Palm Beach Island is located in the foreground; the remainder of Palm Beach 

County can be seen in the background. The intracoastal waterway is dredged between the island and mainland. (NOAA Photo Library) 

Figure 4. Aerial photograph showing sand bars of St.Lucie Inlet. 

The channels between the sand bars migrate and change shape over time. (ESRI’s online World 2D Imagery) 
Friday et al., 2012

4

3. Methodology

The Palm Beach NAVD 88 and MHW DEMs were constructed to meet PMEL specifications (Table 1), based

on input requirements for the development of Reference Inundation Models (RIMs) and Standby Inundation Models

(SIMs) (V. Titov, pers. comm.) in support of NOAA’s Tsunami Warning Centers use of SIFT (Short-term InundationForecasting for Tsunamis) to provide real-time tsunami forecasts in an operational environment. The best available

bathymetric and topographic digital data were obtained by NGDC and shifted to common horizontal and vertical

datums: North American Datum of 19832 (NAD 83) and NAVD 88. An NAVD 88 DEM was developed using the data,

and was shifted to MHW for modeling of maximum flooding using a conversion grid. Data were gathered in an area

slightly larger (~5%) than the DEM extents. This data “buffer” ensured that gridding occurred across rather than along

the DEM boundaries to prevent edge effects. Data processing and evaluation, and DEM assembly and assessment are

described in the following subsections.

 Table 1: Specifications for the Palm Beach DEMs. 

Grid Area Palm Beach, Florida

Coverage Area 80.41o to 79.42o W; 26.29o to 27.31o N

Coordinate System Geographic decimal degrees

Horizontal Datum World Geodetic System of 1984 (WGS 84)

Vertical Datums a) North American Vertical Datum of 1988 (NAVD 88)

b) Mean High Water (MHW)

Vertical Units Meters

Cell Size 1/3 arc-second

Grid Format ESRI Arc ASCII raster grid

2. The horizontal difference between the North American Datum of 1983 (NAD 83) and World Geodetic System of 1984 (WGS 84) geographic

horizontal datums is approximately one meter across the contiguous U.S., which is significantly less than the cell size of the DEMs. Most GIS

applications treat the two datums as identical, so do not actually transform data between them, and the error introduced by not converting between

the datums is insignificant for our purposes. NAD 83 is restricted to North America, while WGS 84 is a global datum. As tsunamis may originate

most anywhere around the world, tsunami modelers require a global datum, such as WGS 84 geographic, for their DEMs so that they can model

the wave’s passage across ocean basins. These DEMs are identified as having a WGS 84 geographic horizontal datum even though the underlying

elevation data were typically transformed to NAD 83 geographic. At the scale of the DEMs, WGS 84 and NAD 83 geographic are identical and

may be used interchangeably.
Digital Elevation Models of Palm Beach, Florida

5

3.1 Data Sources and Processing

Shoreline, bathymetric, and topographic digital datasets were obtained from international, federal, state and

local agencies and institutions (Fig. 5) including: NGDC; NOAA’s National Ocean Service (NOS), Office of Coast

Survey (OCS) and Coastal Services Center (CSC); the U.S. Army Corps of Engineers (USACE); Japan’s Ministry of

Economy, Trade, and Industry (METI); the National Aeronautics and Space Administration (NASA); the Joint Airborne Lidar Bathymetry Center of Expertise (JALBTCX); the South Florida Water Management District (SFWMD);

the County of Palm Beach; and the Florida Department of Emergency Management (FDEM). Datasets were shifted

to NAD 83 geographic horizontal datum using Safe Software’s Feature Manipulation Engine (FME), ESRI’s ArcGIS,

and NOAA’s Vertical Datum (VDatum) transformation tool. Data were visually displayed with ArcGIS and Applied

Imagery’s Quick Terrain Modeler (QT Modeler), to assess quality and manually edit datasets. Most vertical datum

transformations were accomplished using VDatum, although VDatum did not provide transformations for the National

Geodetic Vertical Datum of 1929 (NGVD 29, see Sec. 3.2.1).

Figure 5. Source and coverage of datasets used in compiling the Palm Beach DEMs.
Friday et al., 2012

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3.1.1 Shoreline

Shoreline data of the Palm Beach region were extracted from existing lidar-derived contour data (Table 2).

The contour data were developed by CH2M Hill for the Florida Division of Emergency Management (FDEM), and

were obtained from the Florida Geospatial Data Library (FGDL) web site (http://www.fgdl.org). 

Table 2. Shoreline datasets used in developing the Palm Beach NAVD 88 DEM.

Source Year Data Type Spatial Resolution 

or Scale

Original Horizontal Datum/

Coordinate System

Original Vertical 

Datum URL

FDEM 2009 vector

digital data ~5 meters NAD 83 HARN NAVD 88 ftp://ftp1.fgdl.org/pub/

1) Florida Division of Emergency Management 

 Lidar data of the Florida coastal zones were obtained for FDEM from 2006 -2009. The public lidar

data are available from many organizations in many forms, including DEMs, LAS files, xyz files, and

contour shapefiles. Lidar-derived contour shapefiles were downloaded from the FGDL by county, and the

zero contour lines were extracted from the shapefiles using ArcGIS (Fig. 6). 

The zero lines used in the Palm Beach DEM were assumed to represent the NAVD 88 coastlines for

Broward County, Palm Beach County, Martin County, and St. Lucie County. The coastlines for each of the

four counties were merged together, and slightly adjusted where necessary based on comparisons with aerial

imagery, bathymetric data, wetland and mangrove data, lower resolution coastlines, and NOAA Raster Nautical Charts (RNCs). An xyz file of the adjusted coastline with points located every 10 meters was generated

using NGDC’s GEODAS software, for use in creating the ‘pre-surface’ bathymetric grid (See Sec. 3.3.2).

Figure 6. Portion of lidar-derived contours, shown with extracted zero contour line. 

 The zero contour was used as the Palm Beach DEM coastline. ESRI’s online World 2D Imagery in background.
Digital Elevation Models of Palm Beach, Florida

7

3.1.2 Bathymetry

Bathymetric datasets used in the compilation of the Palm Beach DEMs included extracted points from two

NOS Electronic Navigational Charts (ENCs); a bathymetric lidar survey from JALBTCX; 23 NOS hydrographic surveys; Laser Airborne Depth Soundings (LADS) from Palm Beach County; one hydrographic survey from the South

Florida Water Management District (SFWMD);several hydrographic surveys from the USACE Jacksonville District;

and NGDC digitized points of the intracoastal waterway, based on NOS RNCs and information from the United States

Coast Pilot®. (Table 3; Fig. 7). 

Several other bathymetric datasets were acquired and assessed, but they were superseded by higher quality

or more recent datasets, and so were not used as input in the final DEM. These datasets included multibeam swath

sonar surveys downloaded from the NGDC multibeam database, trackline surveys available from NGDC, and seven

ebb tidal shoal hydrographic surveys available from Palm Beach County.

Table 3. Bathymetric datasets used in compiling the Palm Beach NAVD 88 DEM.

Source Year Data Type Spatial Resolution

Original 

Horizontal Datum/

Coordinate System

Original 

Vertical 

Datum

URL

ENC 2008 to

2009

Extracted

soundings

Digitized from 1:40,000 scale

RNC, point spacing

50 to 1000 meters

NAD 83 Geographic MLLW charts.noaa.gov/ENCs/

ENCs.shtml

JALBTCX 2006 Lidar DEM 1 to 2 meters NAD 83 NAVD 88 http://www.csc.noaa.

gov/ldart

NGDC 2010

Digitized 

point

soundings

Digitized from RNCs of varying resolutions based on depth

information from

the United States Coast Pilot

WGS 84 NAVD 88 n/a

NOS 1883 to

1969

Hydrographic

survey

xyz data

Ranges from less than 10 m

to 600 m (varies with scale of

survey, recentness of survey,

and water depth or distance

from shore)

NAD 83 geographic MLW

HUhttp://www.ngdc.noaa.

gov/mgg/bathymetry/

hydro.htmlUH

Palm

Beach

County

2003 LADS survey

xyz data 2 to 4 meters

State Plane Coordinate System NAD 83,

East Florida Zone

NGVD 29

http://www.pbcgov.com/

erm/coastal/shoreline/

beach/data.htm

SFWMD 1998

Hydrographic

survey point

shapefile

1 meter to 300 meters NAD 83 HARN NGVD 29

http://my.sfwmd.gov/

gisapps/sfwmdxwebdc/

dataview.asp

USACE 2005 to

2010

Hydrographic

survey

xyz data

1 to 10 meters

State Plane

Coordinate System

NAD 27 and NAD

83,

East Florida Zone

MLLW or

MLW

http://www.saj.usace.

army.mil/Divisions/

Operations/Branches/

HydroSurvey/hydro.php
Friday et al., 2012

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Figure 7. Source and coverage of bathymetric datasets used in compiling the Palm Beach DEMs.
Digital Elevation Models of Palm Beach, Florida

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1) Electronic navigational chart soundings

NGDC used FME software to extract bathymetric soundings from ENCs #11472 and #114673

. The

soundings provided depth information in areas where higher resolution bathymetric data were unavailable.

These areas existed in some places between the Florida barrier islands and the mainland (Fig. 8). The ENCs

were downloaded from NOAA’s Office of Coast Survey website, and were horizontally referenced to NAD

83 geographic. The extracted soundings were transformed from a vertical datum of MLLW to NAVD 88 using VDatum. Some soundings were contoured using GEODAS Hydroplot to interpolate point values along

channels and in areas of sparse data.

Figure 8. ENC coverage in the Palm Beach area. 

2) Joint Airborne Lidar Bathymetry Technical Center of Expertise lidar data

Lidar data of the Palm Beach area were acquired from the Coastal Services Center (CSC) website.

These data were collected by JALBTCX, for USACE, as part of the National Coastal Mapping Program in

2006. Only the bathymetric portion of the data were used, because the topographic portion of the data was

not processed to bare-earth. The bathymetric lidar data were vertically referenced to NAVD 88 and were

horizontally referenced to NAD 83 geographic. The JALBTCX lidar data were used to provide coverage for

sections of coast that were not included in the newer Palm Beach County LADS data.

3. The Office of Coast Survey (OCS) produces NOAA Electronic Navigational Charts (NOAA ENC®) to support the marine transportation

infrastructure and coastal management. NOAA ENC®s are in the International Hydrographic Office (IHO) S-57 international exchange format,

comply with the IHO ENC Product Specification and are provided with incremental updates, which supply Notice to Mariners corrections

and other critical changes. NOAA ENC®s are available for free download on the OCS web site. [Extracted from NOAA OCS web site; http://

w1.nauticalcharts.noaa.gov/mcd/enc/index.htm]
Friday et al., 2012

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3) National Geophysical Data Center digitized points

NGDC used information from NOS RNCs and from the United States Coast Pilot® to digitize 1 arcsecond point data of the intracoastal waterway in areas where this data was not otherwise available. The

digitized points were used in the southern area of the DEM, between the barrier islands and the mainland

(see Fig. 9), where SFWMD data and USACE data did not provide coverage. The location of the intracoastal

waterway was acquired from RNCs, and the NAVD 88 depth of the intracoastal waterway was estimated in

the Coast Pilot® to be about 10 feet, or about 3.05 meters.

4) National Ocean Service hydrographic survey data

A total of 23 NOS hydrographic surveys conducted between 1883 and 1969 were available for use in

developing the Palm Beach DEMs (Table 4; Fig. 9). The surveys were extracted from NGDC’s online NOS

hydrographic database using GEODAS4. The hydrographic survey data were downloaded vertically referenced to mean low water (MLW) and horizontally referenced to NAD 83 geographic.

The data point spacing of the surveys varies by scale. In general, small scale surveys have greater point

spacing than large scale surveys. All NOS surveys were converted from MLW to NAVD 88 using the VDatum transformation tool (see Sec. 3.2.1). The data were converted to shapefiles using FME software, and

were edited and clipped to the DEM area in ESRI’s ArcGIS. The surveys were compared to the original

survey smooth sheets, other bathymetric datasets, the Palm Beach lidar coastline, topographic lidar data, and

NOS raster nautical charts (RNCs). Older surveys were clipped to remove soundings that were overlapped

by more recent bathymetric data.

Table 4. Digital NOS hydrographic surveys used in developing the Palm Beach NAVD 88 DEM.

NOS 

Survey ID

Year of 

Survey Area of Survey Survey Scale

Original 

Horizontal Datum

Original 

Vertical Datum

H01570 1883 Indian River- Inlet to Eden 1:20,000 Undetermined MLW

H01571 1883 Indian River - Eden to Jupiter Narrows 1:20,000 Undetermined MLW

H04914 1929 Jupiter Inlet to Lake Worth Inlet 1:20,000 Undetermined MLW

H04930 1929 Hillsboro Inlet to Vicinity of New River Inlet 1:20,000 Undetermined MLW

H04963 1929 Lake Worth Inlet to Hypoluxo Island 1:20,000 Undetermined MLW

H04968 1929 Lake Worth Inlet to Palm Beach 1:10,000 Undetermined MLW

H05015 1929 Villa Rica to Hillsboro Inlet 1:5,000 Undetermined MLW

H05016 1929 Hypoluxo Island to Villa Rica 1:20,000 Undetermined MLW

H05022 1930 St. Lucie Inlet to Lake Worth Inlet 1:20,000 NAD 27 MLW

H05023 1930 St. Lucie Inlet 1:10,000 NAD 27 MLW

H05026 1930 St. Lucie Shoal 1:20,000 NAD 27 MLW

H05031 1930 North of St.Lucie Inlet 1:20,000 NAD 27 MLW

H05040 1930 Fort Pierce Inlet to Pierce Shoal 1:40,000 NAD 27 MLW

H05047 1930 Gilberts Shoal to Jupiter Inlet 1:40,000 NAD 27 MLW

H05057 1930 Fort Pierce Inlet to Gilberts Shoal 1:40,000 NAD 27 MLW

H08782 1964 Atlantic Ocean- East Coast Surveys 1:100,000 NAD 27 MLW

H08783 1964 Atlantic Ocean- East Coast Surveys 1:100,000 NAD 27 MLW

H08953 1967 Jupiter Inlet and Vicinity 1:10,000 NAD 27 MLW

H08954 1967 St. Lucie Inlet and Vicinity 1:10,000 NAD 27 MLW

H08955 1967 Coastline North of Jupiter Inlet 1:20,000 NAD 27 MLW

H08956 1967 Gilbert Shoal and Vicinity 1:20,000 NAD 27 MLW

H08957 1967 Coastline South of Fort Pierce 1:20,000 NAD 27 MLW

H09007 1969 Loxahatchee River 1:10,000 NAD27 MLW

4. GEODAS uses the North American Datum Conversion Utility (NADCON; http://www.ngs.noaa.gov/TOOLS/Nadcon/Nadcon.shtml) developed

by NOAA’s National Geodetic Survey (NGS) to convert hydrographic survey data from NAD 27 to NAD 83. NADCON is the U.S. Federal

Standard for NAD 27 to NAD 83 datum transformations.
Digital Elevation Models of Palm Beach, Florida

11

Figure 9. NOS hydrographic survey coverage in the Palm Beach region. Red box represents DEM extents.
Friday et al., 2012

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5) Palm Beach County Laser Airborne Depth Soundings

LADS data for the Palm Beach area were released in 2003. The Palm Beach County Environmental

Resources Manangement division contracted the data collection through Coastal Planning and Engineering,

Inc.Processed xyz files provide bathymetric nearshore coverage (see Fig. 10), and are available through Palm

Beach County’s Environmental Resources Management website. The data were provided to NGDC, however, via ftp by Brian K. Walker, Ph.D, of the National Coral Reef Institute at Nova Southeastern University.

The Palm Beach County LADS data were referenced to NGVD 29. VDatum software does not provide

transformations from this vertical datum, so the data were transformed to NAVD 88 using an averaged constant from tide stations in the Palm Beach area (See Sec. 3.2.1). The LADS data were converted from NAD

83 Florida State Plane East Florida Zone to WGS 84 using FME, and were clipped to the Palm Beach lidar

derived coastline. The data are of a high level of accuracy (International Hydrographic Organization Order

1), and reveal near shore bathymetric irregularities such as dredging holes and established reefs.

Figure 10. Spatial Coverage of the Palm Beach County LADS data.
Digital Elevation Models of Palm Beach, Florida

13

6) Southern Florida Water Management District Hydrographic Surveys

Hydrographic surveys for the St. Lucie Estuary, north of Palm Beach County, were acquired in 1998,

and were processed and distributed as shapefiles on behalf of the SFWMD (see Fig. 11). The data consist of

channel profiles spaced ~300 meters apart. The points were horizontally referenced to NAD 83 HARN and

vertically referenced to NGVD 29. The data were converted to xyz points, and triangulated using the GMT

‘triangulate’ tool to provide a surface more representative of the actual bathymetry (see Fig. 12).

Figure 11. Spatial coverage of the SFWMD hydrographic survey in St.Lucie estuary. 

Figure 12. Comparison of original SFWMD hydrographic survey xyz points and NGDC triangulated surface. The image on the left shows a 

portion of the original SFWMD hydrographic survey data, acquired as channel profiles and spaced at 300 meters. 

NGDC triangulated this data to create a more uniform coverage surface, shown on the right. 

This triangulated surface better represented the bathymetry of the area, especially the intracoastal waterway (dark blues). 
Friday et al., 2012

14

7) U.S. Army Corps of Engineers hydrographic surveys

Six line survey datasets were downloaded from the USACE Jacksonville District website for use in

building the Palm Beach DEMs (Table 5; Fig. 13). The surveys provided depth information for important

navigational channels and dredged areas along the coast.

The surveys were horizontally referenced to Florida State Plane Coordinate System East Zone of NAD

83 or NAD 27. The data were transformed to NAD 83 geographic using FME. The surveys were vertically reference to either MLW or MLLW, and were transformed to NAVD 88 using VDatum software. The

USACE line surveys consist of dense data profiles across dredged channels that are sparsely staggered, and

so were triangulated using the GMT ‘triangulate’ tool to provide a more representative surface (See Fig. 12).

Table 5. USACE hydrographic surveys used in compiling the Palm Beach DEMs.

Survey ID 

Number Survey Name Date

Original 

Vertical 

Datum

Original Horizontal Datum Resolution

98-183 Okeechobee Waterway,

St.Lucie River, Florida July 1998 MLW NAD 27Florida State Plane East Zone ~ 5 to 30 meters

01-092 Okeechobee Waterway,

St. Lucie Canal, Florida May 2001 MLLW NAD 27Florida State Plane East Zone ~ 5 to 30 meters

07-079

Intracoastal Waterway,

Palm Beach County,

Florida

April 2010 MLW NAD 27

Florida State Plane East Zone ~ 5 to 30 meters

08-106 Intracoastal Waterway,

Martin County, Florida September 2008 MLW NAD 83Florida State Plane East Zone ~ 5 to 30 meters

09-029 St. Lucie Inlet, Florda April 2009 MLLW NAD 83

Florida State Plane East Zone ~ 5 to 30 meters

10-051 Palm Beach Harbor,

Florida March 2010 MLLW NAD 83Florida State Plane East Zone ~ 5 to 30 meters
Digital Elevation Models of Palm Beach, Florida

15

Figure 13. Spatial coverage of USACE hydrographic survey data in the vicinity of Palm Beach.
Friday et al., 2012

16

3.1.3 Topography

Two topographic datasets in the Palm Beach region were used to build the Palm Beach NAVD 88 DEM

(Table 6; Fig. 14). The FDEM lidar dataset included lidar projects from two separate years. NASA SRTM data were

used to fill holes where lidar data were unavailable. USGS NED data and ASTER data were assessed, but were not

used in the final DEM due to quality issues.

Table 6. Topographic datasets used in compiling the Palm Beach DEMs.

Source Year Data Type Spatial Resolution

Original Horizontal 

Datum/Coordinate 

System

Original 

Vertical 

Datum

URL

FDEM 2006-

2009 Lidar 5-7 meters NAD 83 geographic NAVD 88

http://my.sfwmd.gov/gisapps/

sfwmdxwebdc/dataview.asp?/ and

http://csc.noaa.gov/digitalcoast/

NASA 1999 SRTM 1 arc-second NAD 83 geographic NAVD 88 http://ned.usgs.gov/

Figure 14. Source and coverage of topographic datasets used in compiling the Palm Beach DEMs.
Digital Elevation Models of Palm Beach, Florida

17

1) Florida Department of Emergency Management Coastal Lidar

The topographic lidar datasets used in compiling the Palm Beach DEM were collected in 2006 and 2009

for a variety of organizations, including FDEM, the Florida Water Management Districts, the Florida Fish

and Wildlife Conservation Commission, the Florida Department of Environmental Protection, the USACE

Jacksonville District, and other state and federal agencies. The ultimate goal of this project was to use the

lidar data as new elevation inputs for updated Sea, Lake, and Overland Surges from Hurricanes (SLOSH)

data grids, resulting in updates of the Regional Hurricane Evacuation Studies (RHES; http://www.saw.usace.

army.mil/floodplain/Hurricane%20Evacuation.htm) for the state.

FDEM coastal lidar for Palm Beach County and Broward County were provided to NGDC asraster DEM

datasets from the FDEM GIS Administrator, Richard Butgereit. FDEM coastal lidar data for Martin County

and St. Lucie County were obtained online asraster DEM datasetsfrom the SFWMD online GIS Data Catalog. 

The 2009 coastal lidar data for all four counties were horizontally referenced to NAD 83 Florida State Plane

West (feet) and vertically referenced to NAVD 88. The data were transformed from feet to meters and to

WGS 84 geographic using ArcGIS. The coastal lidar data were edited to remove bridges, and were converted

to xyz points to be used in the final gridding process. 

NGDC obtained inland xyz lidar data from NOAA CSC website. The inland lidar data were horizontally referenced to WGS 84 geographic and were vertically referenced to NAVD 88; no transformations were

necessary. The inland lidar data were edited to remove some roads and buildings that remained, and were

converted to xyz points to be used in the final gridding process

All FDEM lidar data were clipped to the Palm Beach lidar-derived coastline in order to remove empty

data values over the open ocean. This prevented empty values from overlapping with the bathymetric datasets used in compiling the Palm Beach DEMs..

2) Shuttle Radar Topography Mission InSAR data

The SRTM was a joint international project run by the National Geospatial Intelligence Agency (NGA)

and NASA5. In 2000, the SRTM project obtained global elevation data at 1 arc-second resolution using an interferometric synthetic aperature rader (InSAR) system. Two SRTM raster grid tiles were downloaded from

the SRTM webstie for use in the Palm Beach DEM; the data were used to provide coverage in the northwest

and southwest inland portions of the Palm Beach DEM topography, where FDEM lidar data was unavailable. 

SRTM data were referenced to the WGS 84 horizontal datum and were assumed to be vertically referenced based on the Earth Gravitational Model (EGM) 1996 Geoid. NGDC used a conversion grid and VDatum to convert the data to NAVD 88 based on the 2009 Geoid (See Sec. 3.2.1).

The SRTM dataset was the best coverage option when compared to ASTER and NED datasets, but the

SRTM dataset contained many water returns due to the marshy nature of the area, and were non-bare earth

so contained canopy values. NGDC edited the SRTM data in order to remove canopy heights and to smooth

water returns, but the SRTM was still inconsistent with the FDEM lidar data. In many places along the seam

of the two datasets, a step in data values is visible in the Palm Beach DEM. To minimize the modeling effects

of the step, an empty buffer was installed between the datasets to allow for smoothing and interpolation at the

seam.

5. The SRTM data setsresult from a collaborative effort by the NationalAeronautics and SpaceAdministration (NASA) and the National GeospatialIntelligence Agency (NGA – previously known as the National Imagery and Mapping Agency, or NIMA), as well as the participation of the German

and Italian space agencies, to generate a near-global digital elevation model (DEM) of the Earth using radar interferometry. The SRTM instrument

consisted of the Spaceborne Imaging Radar-C (SIR-C) hardware set modified with a Space Station-derived mast and additional antennae to form

an interferometer with a 60 meter long baseline. A description of the SRTM mission can be found in Farr and Kobrick (2000). Synthetic aperture

radars are side-looking instruments and acquire data along continuous swaths. The SRTM swaths extended from about 30 degrees off-nadir to

about 58 degrees off-nadir from an altitude of 233 km, and thus were about 225 km wide. During the data flight the instrument was operated at all

times the orbiter was over land and about 1000 individual swaths were acquired over the ten days of mapping operations. Length of the acquired

swaths range from a few hundred to several thousand km. Each individual data acquisition is referred to as a “data take.” SRTM was the primary

(and pretty much only) payload on the STS-99 mission of the Space Shuttle Endeavour, which launched February 11, 2000 and flew for 11 days.

Following several hours for instrument deployment, activation and checkout, systematic interferometric data were collected for 222.4 consecutive

hours. The instrument operated almost flawlessly and imaged 99.96% of the targeted landmass at least one time, 94.59% at least twice and about

50% at least three or more times. The goal was to image each terrain segment at least twice from different angles (on ascending, or north-going, and

descending orbit passes) to fill in areas shadowed from the radar beam by terrain. This ‘targeted landmass’ consisted of all land between 56 degrees

south and 60 degrees north latitude, which comprises almost exactly 80% of Earth’s total landmass. [Extracted from SRTM online documentation;

http://srtm.usgs.gov/]
Friday et al., 2012

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3.2 Establishing Common Datums

3.2.1 Vertical datum transformations

Datasets used in the compilation of the Palm Beach NAVD 88 DEM were originally referenced to a number

of vertical datums including MLW, MLLW, NGVD 29, and NAVD 88. All datasets were transformed to NAVD 88 using the VDatum transformation tool (http://vdatum.noaa.gov/), except for those referenced to NGVD 29, which were

transformed using an averaged constant based on local tide station values (Fig.15). The locations and tidal relationships at the Palm Beach area tide stations (http://tidesandcurrents.noaa.gov/) are provided in Table 7.

1) Bathymetric data

The ENC extracted soundings, JALBTCX lidar surveys, NOS hydrographic surveys, and USACE hydrographic surveys were transformed from MLLW and MSL to NAVD 88 using VDatum. LADS data and

SFWMD data in NGVD 29 were transformed to NAVD 88 using a constant value of 0.47 meters, averaged

from the values at all tide stations (Table 7).

2) Topographic data

All FDEM lidar datasets were originally referenced to NAVD 88, and required no vertical transformations. SRTM data were transformed from the EGM 1996 Geoid to the NAVD 88 Geoid 2009 using a

geoid height transformation grid acquired from the National Geospatial Intelligence Agency (http://earthinfo.nga.mil/GandG/wgs84/gravitymod/egm96/egm96.html) and VDatum.

Table 7. Tide stations in the Palm Beach area and relationships between NGVD 29 and NAVD 88.

 Tide Station Name Difference

NGVD 29 to NAVD 88 (m) Latitude Longitude

8722472 North Loxachatchee River 0.458 26.9867 -80.1417

8722481 Loxachatchee River 0.54 26.97 -80.1267

8722478 North Fork Loxachatchee River 0.456 26.9867 -80.1417

8722486 Tequesta, North Fork, Loxachatchee River 0.458 26.975 -80.1133

8722488 Tequesta, Loxachatchee River n/a 26.9517 -80.1017

8722487 Tequestra n/a 26.9517 -80.1017

8722496 Loxachatchee River Lock 0.46 26.935 -80.143

8722492 Jupiter West n/a 26.9467 -80.09

8722491 Jupiter Sound 0.459 26.9517 -80.08

8722495 Jupiter Inlet n/a 26.9433 -80.0733

8722512 Lake Worth Creek 0.446 26.9117 -80.08

8722548 PGA Boulevard Bridge 0.461 26.8433 -80.0667

8722557 North Palm Beach 0.472 26.8267 -80.055

8722588 Port of West Palm Beach, Lake Worth n/a 26.77 -80.0517

8722607 Palm Beach 0.462 26.733 -80.0417

8722621 Palm Beach Brazilian Dock 0.464 26.705 -80.045

8722654 West Palm Beach 0.497 26.645 -80.045

8722670 Lake Worth Pier 0.468 26.6117 -80.0333

8722706 Boynton Beach 0.476 26.5483 -80.0533

8722746 Delray Beach 0.473 26.4733 -80.0617

8722761 South Delray Beach 0.472 26.4467 -80.065

8722784 Yamato 0.469 26.4033 -80.07
Digital Elevation Models of Palm Beach, Florida

19

 Tide Station Name Difference

NGVD 29 to NAVD 88 (m) Latitude Longitude

8722802 Lake Wyman 0.556 26.37 -80.07

8722445 Hobe Sound State Park 0.453 27.0367 -80.1067

8722429 Hobe Sound Bridge 0.451 27.065 -80.1233

8722414 Gomez 0.455 27.0933 -80.1367

8722404 Peck Lake 0.449 27.1133 -80.145

8722381 Great Pocket 0.444 27.155 -80.1717

8722383 Port Salerno 0.442 27.1517 -80.195

8722371 Sewall Point 0.444 27.175 -80.1883

8722357 Stuart 0.446 27.2 -80.2583

8722334 North Fork, St. Lucie River 0.45 27.2433 -80.3133

Average 0.47

Figure 15. Locations of NOAA tide stations in the Palm Beach area.
Friday et al., 2012

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3.2.2 Horizontal datum transformations

Datasets used in the compilation of the Palm Beach NAVD 88 DEM were originally referenced to WGS 84

geographic, NAD 83 geographic, NAD 83 State Plane Coordinate System East Florida Zone, and NAD 27 State Plane

Coordinate System East Florida Zone horizontal datums. The relationships and transformational equations between

these geographic horizontal datums are well established. Transformations to NAD 83 geographic were accomplished

using FME, ArcGIS, and VDatum software.
Digital Elevation Models of Palm Beach, Florida

21

3.3 Digital Elevation Model Development

3.3.1 Verifying consistency between datasets

After horizontal and vertical transformations were applied, the resulting data were viewed in ArcMap and QT

Modeler for consistency. Any problems and errors were identified and resolved before proceeding with subsequent

gridding steps. Once evaluated, compared, and corrected, the data were converted into final xyz files in preparation for

the DEM gridding process. Problems included:

•	 Inconsistent overlapping datasets. Older data sometimes overlapped newer data, and data values varied

between the years. Older data were eliminated in these areas. Data were also weighted during the final

gridding process based on resolution, quality, and age.

•	 Topograhic lidar data values over the bathymetric portions of DEM. Some topographic lidar data contained

water-return or empty values over the open ocean, which needed to be clipped from the datasets using the

Palm Beach coastline.

•	 Inconsistencies between lidar data and SRTM data. These inconsistencies were caused by water returns in

swamps, and the bare-earth or non- bare-earth nature of the datasets. The SRTM data were removed where

they were overlapped by higher quality, bare-earth lidar, and were edited to remove canopy values and water

return values. A small buffer was also used between the two datasets to allow for interpolation between them. 

This prevented the appearance of a “step” or “wall” in the final DEM where the datasets meet.

•	 Outdated NOS data. Bathymetric values from NOS surveys dated back over 100 years. More recent data,

such as the Palm Beach County LADS data, differed from old NOS data by as much as 50 meters vertically.

The older NOS survey data were removed where more recent bathymetric data exists.

•	 Non-bare-earth values in lidar datasets from buildings, lakes, and bridges. Obvious non-bare-earth returns

were manually removed from the lidar data.

•	 Inconsistencies between NGDC digitized points along the intracoastal waterway and SFWMD and USACE

hydrographic data. Digitized points were removed where other data existed.

•	 Staggered spacing of dense channel profile coverage in the SFWMD and USACE hydrographic surveys

due to data collection techniques. These data were triangulated before gridding to create a more uniform

coverage surface.

3.3.2 Smoothing of bathymetric data

The older NOS hydrographic survey data are generally sparse at the resolution of the Palm Beach DEMs.

To reduce the effect of artifacts due to this, a 1 arc-second cell size ‘pre-surface’ bathymetric grid in NAVD 88 vertical datum was generated using GMT6

, an NSF-funded share-ware software application designed to manipulate data

for mapping purposes (HUhttp://gmt.soest.hawaii.edu/UH). Additionally, a near-shore 1/3 arc-second cell size ‘pre-surface’

bathymetric grid in NAVD 88 was created, to prevent the interpolation of positive values from known ocean areas.

To create the bathymetric surfaces, all bathymetric datasets were converted into xyz points, and were combined with points extracted from the Palm Beach coastline—to provide a breakline along the entire coastline. The

coastline elevation values were set to -0.85 meters, to ensure the bathymetric surface approached zero relative to

NAVD 88 in areas where bathymetric data are sparse or non-existent.

The point data were then median-averaged using the GMT tool ‘blockmedian’ to create a 1 arc-second grid

0.05 degrees (~5%) larger than the Palm Beach DEM region, and a near-shore 1/3 arc-second coverage grid. The GMT

tool ‘surface’ was used to apply a tight spline tension to interpolate elevations for cells without data values. The GMT

grid created by ‘surface’ was converted into an ESRI Arc ASCII grid file, and clipped to the Palm Beach coastline .

The resulting surface was compared with original bathymetric soundings to ensure grid accuracy, and to be

certain that the real data quality was not being affected. Examples of these comparisons are shown in Figures 16 and

17, which show histograms of the NOS and total bathymetric data xyz points, respectively, compared to the 1 arc-second pre-surfaced bathymetric grid. Differences cluster around zero with a range of -9 to +15 meters when compared

to the bathymetric surface. Points with the largest differences are located where dense data contain multiple elevation

9. GMT is an open source collection of ~60 tools for manipulating geographic and Cartesian data sets (including filtering, trend fitting, gridding,

projecting, etc.) and producing Encapsulated PostScript File (EPS) illustrations ranging from simple x-y plots via contour maps to artificially

illuminated surfaces and 3-D perspective views. GMT supports ~30 map projections and transformations and comes with support data such as

GSHHS coastlines, rivers, and political boundaries. GMT is developed and maintained by Paul Wessel and Walter H. F. Smith with help from a

global set of volunteers, and is supported by the National Science Foundation. It is released under the GNU General Public License. URL: http://

gmt.soest. hawaii.edu/ [Extracted from GMT web site.]
Friday et al., 2012

22

values per cell, which were averaged to create the final DEM value.

The gridded bathymetric surfaces were converted into xyz files for use in building the final Palm Beach

NAVD 88 DEM (See Sec. 3.3.3).

Figure 16. Histogram of the differences between the NOS bathymetric surveys and the 1 arc-second pre-surfaced bathymetric grid. 

Figure 17. Histogram of the differences between all original bathymetric data and the 1 arc-second pre-surfaced bathymetric grid. 
Digital Elevation Models of Palm Beach, Florida

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3.3.3 Building the NAVD 88 DEM

MB-System7 was used to create the 1/3 arc-second Palm Beach NAVD 88 DEM. The MB-System tool ‘mbgrid’ was used to apply a tight spline tension to the xyz data, and interpolate values for cells without data. The

data hierarchy used in the ‘mbgrid’ gridding algorithm, as relative gridding weights, is listed in Table 8. The

greatest weights were assigned to the lidar datasets, the bathymetric surface, and the Palm Beach County LADS

data. The least weight was given to the SRTM data, ENC extracted soundings, and NGDC digitized points.

Table 8. Data hierarchy used to assign gridding weight in MB-System.

Dataset Relative Gridding Weight

SRTM InSAR Data 0.1

FDEM Topographic Lidar 1

ENC Extracted Soundings 1

Lidar Derived Coastline Extracted Points 1

NGDC Digitized Intracoastal Waterway Points 1

NOS Hydrographic Soundings 10

USACE Hydrographic Soundings 10

SFWMD Hydrographic Soundings 10

JALBTCX Bathymetric Lidar 100

Palm Beach County LADS 100

Pre-Surfaced Bathymetric Grid 100

3.3.4 Building the MHW DEM 

The MHW DEM was created by adding an “NAVD 88 to MHW” conversion grid to the NAVD 88 DEM.

1) Developing the conversion grid

Using extents slightly larger (~ 5 percent) than the DEM, an initial xyz file was created that contained the

coordinates of the four bounding vertices and midpoint of the area. The elevation value at each of the points

was set to zero. The GMT tool ‘surface’ applied a tension spline to interpolate cell values, making a zerovalue 3 arc-second grid. This zero-value grid was then converted to an intermediate xyz file using the GMT

tool ‘grd2xyz’. Conversion values from NAVD 88 to MHW at each xyz point were generated using VDatum

and the null values were removed. NGDC used the GMT tool ‘blockmedian’ to median-average multiple

elevation values where VDatum project areas overlapped.

The median-averaged xyz file was then interpolated with the GMT tool ‘surface’ to create the 1/3 arcsecond ‘NAVD 88 to MHW’ conversion grid with the extent of the Palm Beach DEMs, interpolating values

inland to represent the differences between the two datums onshore (Fig. 18).

7. MB-System is an open source software package for the processing and display of bathymetry and backscatter imagery data derived from

multibeam, interferometry, and sidescan sonars. The source code for MB-System is freely available (for free) by anonymous ftp (including “point

and click” access through these web pages). A complete description is provided in web pages accessed through the web site. MB-System was

originally developed at the Lamont-Doherty Earth Observatory of Columbia University (L-DEO) and is now a collaborative effort between

the Monterey Bay Aquarium Research Institute (MBARI) and L-DEO. The National Science Foundation has provided the primary support for

MB-System development since 1993. The Packard Foundation has provided significant support through MBARI since 1998. Additional support

has derived from SeaBeam Instruments (1994-1997), NOAA (2002-2004), and others. URL: http://www.ldeo.columbia.edu/res/pi/MB-System/

[Extracted from MB-System web site.]
Friday et al., 2012

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Figure 18. Image of NGDC Palm Beach conversion grid. 

The conversion values represent the difference between NAVD 88 and MHW, as determined from VDatum and further interpolation.
Digital Elevation Models of Palm Beach, Florida

25

2) Assessing the accuracy of the conversion grid

The NAVD 88-to-MHW conversion grid was assessed using the NOS survey data. The NOS hydrographic survey data were transformed from MLLW to NAVD 88, and from MLLW to MHW, using VDatum.

Null values were removed and the elevation differences between the MHW and NAVD 88 values were meaured (Fig. 19). A new xyz file was created, containing these difference values.

The accuracy of the 1/3 arc-second conversion grid was checked by comparing the ‘NAVD 88-to-MHW’

grid to the NOS conversion difference xyz file. The results indicated agreement to approximately +/- 0.2

meters with a mean difference of 0.00008 meters.

Figure 19. Histogram of the differences between the conversion grid and xyz difference files using NOS hydrographic survey data.

3) Creating the MHW DEM

Once the NAVD 88 DEM was complete and assessed for errors, the conversion grid was added to it using

ArcCatalog. The resulting MHW DEM was reviewed and assessed using RNCs, USGS topographic maps,

and ESRI World 2D imagery.
Friday et al., 2012

26

3.4 Quality Assessment of the DEMs

3.4.1 Horizontal accuracy

The horizontal accuracy of topographic and bathymetric features in the Palm Beach DEMs is dependent

upon DEM cell size and source datasets. Topographic features have an estimated horizontal accuracy of 10-30 meters:

gridded lidar data have an accuracy less than five meters, and SRTM data are accurate to approximately 30 meters. 

Bathymetric features are resolved to within a few tens of meters in deep-water areas. Shallow, near-coastal regions,

rivers, and harbor surveys have an accuracy approaching that of sub-aerial topographic features. Positional accuracy

is limited by the sparseness of deep-water soundings and potentially large positional uncertainty of pre-satellite navigated (e.g., GPS) NOS hydrographic surveys.

3.4.2 Vertical accuracy

Vertical accuracy of elevation values in the Palm Beach DEMs is also dependent upon the source datasets

contributing to DEM cell values. Topographic data have an estimated vertical accuracy less than 1 meter for bare-earth

lidar data and 20 meters for non bare-earth SRTM DEMs. Bathymetric values have an estimated accuracy between 0.1

meters and 5% of water depth. The values were derived from a wide range of sounding measurements, from the late

nineteenth century to recent, GPS-navigated LADS surveys. Gridding interpolation to determine bathymetric values

between sparse, poorly located NOS soundings degrades the vertical accuracy of elevations in deep water.

3.4.3 Slope map and 3-D perspectives

ESRI ArcCatalog was used to generate a slope grid from the Palm Beach NAVD 88 DEM to allow for visual

inspection and identification of artificialslopes along boundaries between datasets(Fig. 20).The DEM wastransformed

to NAD 83 UTM Florida East Zone coordinates (horizontal units in meters) in ArcCatalog for derivation of the slope

grid; equivalent horizontal and vertical units are required for effective slope analysis. Analysis of preliminary grids using QT Modeler and Fledermausrevealed suspect data points, which were corrected before recompiling the DEM. Figure 1 shows a color image of the 1/3 arc-second Palm Beach NAVD 88 DEM in its final version. The transition in topographic high-resolution bare-earth lidar and low resolution non bare-earth SRTM data can be seen. Figure 21 shows a

perspective rendering of the final NAVD 88 DEM. Figure 22 shows a data contribution plot of the Palm Beach DEMs.
Digital Elevation Models of Palm Beach, Florida

27

Figure 20. Slope map of the Palm Beach NAVD 88 DEM. Flat-lying slopes are shown in white; dark shading denotes steep slopes; combined 

coastline indicated in red.
Friday et al., 2012

28

Figure 21. Perspective view from the northeast of the 1/3 arc-second Palm Beach NAVD 88 DEM. Vertical exaggeration–times 5. 

Figure 22. Data contribution plot of the Palm Beach NAVD 88 DEM. Grey depicts DEM cells constrained by source data; 

white depicts cells with elevation values derived from interpolation. Coastline is shown in red; DEM boundary in black. 
Digital Elevation Models of Palm Beach, Florida

29

3.4.4 Comparison with National Geodetic Survey geodetic monuments

The elevations of 2236 geodetic monuments were extracted from the NOAA NGS web site (http://www.

ngs.noaa.gov/) in shapefile format (see Fig. 23 for monument locations). The associated shapefile attributes provided

high accuracy monument postions in NAD 83 geographic, and elevations in NAVD 88. These elevation data were

compared to the Palm Beach NAVD 88 DEM elevation values (Fig. 24). Differences between the DEM and the monument elevations range from -15.24510 to 89.75030 meters, with a mean of 1.3 meters. Large differences in elevations

occurred where monuments are located on major roads and bridges, pilings, or buildings, and in areas where the grid

elevations were derived from the SRTM data.

Figure 23. Location of NGS geodetic monuments in the Palm Beach region. 

Figure 24. Histogram of the differences between NGS geodetic monument elevations and the Palm Beach NAVD 88 DEM. 
Friday et al., 2012

30

3.4.5 NAVD 88 DEM comparison with source data files

To ensure grid accuracy, the Palm Beach NAVD 88 DEM was compared to source data files. Select bathymetric data and topographic data files were compared to the Palm Beach NAVD 88 DEM.

The deep-water portions of the NOS hydrographic survey dataset was the first compared to the Palm Beach

NAVD 88 DEM (Fig. 25). The differences in elevations are clustered around zero and the majority are within ± 2.5

meters. These values are very accurate because NOS was the only available data in the deep-water areas of the DEM.

The shallow-water portions of the NOS hydrographic survey dataset was also compared to the Palm Beach NAVD 88

DEM (Fig. 26). These values are clustered around zero, but vary by ± 5 meters. The age of the shallow-water NOS

data, which were collected over fifty years ago, probably causes these differences where the shallow-water NOS data

meets more recent datasets, such as the USACE hydrographic surveys.

Comparisons of the USACE hydrographic survey data and the Palm Beach NAVD 88 DEM are shown in

Figure 27. Elevation differences range from -9.15840 to 5.74300 meters. Differences from the grid occur where the

USACE data overlaps other high-resolution datasets, such as the JALBTCX lidar data and the Palm Beach County

LADS data at the mouth of inlets. A difference histogram comparing the SFWMD hydrographic survey dataset with

the Palm Beach NAVD 88 DEM is shown in figure 28. The largest differences (± 3 meters) between the SFWMD data

and the final grid also occur where the data overlap other datasets.

Comparisons of the bathymetric JALBTCX lidar data and the Palm Beach County LADS data against the

NAVD 88 DEM are shown in figures 29 and 30. The differences in elevation cluster around zero, with the JALBTCX

lidar data varying by about ± 6 meters and the LADS data varying by about ± 4 meters. These differences occur where

the high-resolution datasets meet the coast and are affected by interpolation with topographic data, and also where the

data meet other bathymetric datasets, such as the USACE and NOS hydrographic survey datasets.

FDEM topographic lidar data was compared to the grid (Fig. 31), and showed very little differences. A small

amount of points differed by ± 4 meters, and all of these points were located near data boundaries, such as the coastline

and the area where the lidar meets the SRTM data. 

Lastly, the SRTM data was compared to the grid (Fig. 32) and it showed significant differences from the

DEM. It did not overlap with other data sets, but was non-bare earth data, and so the result was expected as the data

were edited and were allowed to interpolate in some areas.

Figure 25. Histogram of the differences between the deep water portion of the Palm Beach NOS DEM data points and the NAVD 88 DEM.
Digital Elevation Models of Palm Beach, Florida

31

Figure 26. Histogram of the differences between the shallow water portion of the Palm Beach NOS DEM data points and the NAVD 88 DEM. 

Figure 27. Histogram of the differences between the Palm Beach USACE hydrographic survey DEM data points and the NAVD 88 DEM. 

Figure 28. Histogram of the differences between the SFWMD hydrographic survey DEM data points and the NAVD 88 DEM.
Friday et al., 2012

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Figure 29. Histogram of the differences between the Palm Beach JALBTCX lidar survey DEM data points and the Palm Beach NAVD 88 DEM. 

Figure 30. Histogram of the differences between the Palm Beach County LADS DEM data points and the Palm Beach NAVD 88 DEM. 

Figure 31. Histogram of the differences between FDEM lidar surveys DEM data points and the Palm Beach NAVD 88 DEM. 
Digital Elevation Models of Palm Beach, Florida

33

Figure 32. Histogram of the differences between SRTM DEM data points and the Palm Beach NAVD 88 DEM. 

4. Summary and Conclusions

Two integrated bathymetric–topographic digital elevation models of the Palm Beach, Florida region, with

cell sizes of 1/3 arc-second, were developed for the Pacific Marine Environmental Laboratory (PMEL), NOAA Center

for Tsunami Research. The best available digital data from U.S. federal, state, local, and academic agencies were obtained by NGDC, shifted to common horizontal and vertical datums, and evaluated and edited before DEM generation.

The data were quality checked, processed and gridded using ESRI ArcGIS, ESRI ArcGIS World Imagery 2-D, FME,

Fledermaus, GMT, MB-System, QT Modeler, and VDatum software.

Recommendations to improve the Palm Beach DEM, based on NGDC’s research and analysis, are listed below:

•	 Conduct surveys to improve topographic data coverage of inland areas.

•	 Conduct additional bathymetric-topographic lidar surveys along the coast.

•	 Conduct high-resolution bathymetric surveys in deep water areas.

•	 Conduct surveys along the entire Intracoastal Waterway.

5. Acknowledgments

The creation of the Palm Beach DEM was funded by the NOAA Pacific Marine Environmental Laboratory.

The authors thank Nazila Merati, Marie Eble, and Vasily Titov (PMEL); Brian Walker (National Coral Reef Institute, 

Nova Southeastern University); Daniel Bates (Palm Beach County Environmental Enhancement and Restoration

Division); Kathleen O’Keife (Florida Fish and Wildlife Conservation Commission); Barbara Herrmann Welch (South

Florida Water Management District); and Vikki Morrow (Broward County GIS Manager).

6. References

Caldwell, R.J., L.A. Taylor, B.W. Eakins, K.S. Carignan, P.R. Medley, E. Lim, and D.Z. Friday. Digital Elevation

Model of Santa Monica, California: Procedures, Data Sources and Analysis. 2010. NOAA Technical

Memoradum NESDIS NGDC-30. http://www.ngdc.noaa.gov/mgg/inundation/tigp/ngdc/data/santa_monica_

ca/santa_monica_ca.pdf

Coast Pilot 4, 41st Edition, 2009. Atlantic Coast: Cape Henry to Key West, FL. U.S. Department of Commerce,

NOAA, National Ocean Service.

Nautical Chart #11428 (RNC), 35th Edition, 2008. St.Lucie Inlet to Fort Meyers and Lake Okeechobee. Scales

1:25,000; 1:40,000; 1:80,000. U.S. Department of Commerce, NOAA, National Ocean Service, Coast Survey.

Nautical Chart #11466 (ENC and RNC), 38th Edition, 2008. Jupiter Inlet to Fowey Rocks. Scales 1:10,000 and

1:80,000. U.S. Department of Commerce, NOAA, National Ocean Service, Coast Survey.
Friday et al., 2012

34

Nautical Chart #11467 (ENC and RNC), 16th Edition, 2010. Intracoastal Waterway- West Palm Beach to Miami. Scale

1:24,000 and 1:40,000. U.S. Department of Commerce, NOAA, National Ocean Service, Coast Survey.

Nautical Chart #11460 (ENC and RNC), 42nd Edition, 2009. Cape Canaveral to Key West. Scale 1:466,940. U.S.

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

Nautical Chart #11474 (ENC and RNC), 10th Edition, 2000. Bethel Shoal to Jupiter Inlet. Scale 1:80,000. U.S.

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

Nautical Chart #11472 (ENC and RNC), 34th Edition, 2009. Palm Shores to West Palm Beach. Scale 1:40,000. U.S.

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

7. Data Processing Software

ArcGIS v. 9.3.1 – developed and licensed by ESRI, Redlands, California, HUhttp://www.esri.com/UH

ESRI World Imagery (ESRI_Imagery_World_2D) – ESRI ArcGIS Resource Centers http://resources.esri.com/

arcgisonlineservices/.

FME 2010 GB – Feature Manipulation Engine, developed and licensed by Safe Software, Vancouver, BC, Canada,

HUhttp://www.safe.com/UH

Fledermaus v. 6.7.0 and 7.0.0 – developed and licensed by Interactive Visualization Systems (IVS 3D), Fredericton,

New Brunswick, Canada, http://www.ivs3d.com/.

GEODAS v. 5 – Geophysical Data System, freeware developed and maintained by Dan Metzger, NOAA National

Geophysical Data Center, HUhttp://www.ngdc.noaa.gov/mgg/geodas/UH

GMT v. 4.3.4 – Generic Mapping Tools, freeware developed and maintained by Paul Wessel and Walter Smith, funded

by the National Science Foundation, HUhttp://gmt.soest.hawaii.edu/UH

MB-System v. 5.1.0 – shareware developed and maintained by David W. Caress and Dale N. Chayes, funded by the

National Science Foundation, HUhttp://www.ldeo.columbia.edu/res/pi/MB-System/UH

Quick Terrain Modeler v. 7.0.2 – LiDAR processing software developed by John Hopkins University’sApplied Physics

Laboratory (APL) and maintained and licensed by Applied Imagery, HUhttp://www.appliedimagery.com/UH

VDatum Transformation Tool, Florida/Georgia - Fort Lauderdale to Sapelo Island, v. 01 – developed and maintained

by NOAA’s National Geodetic Survey (NGS), Office of Coast Survey (OCS), and Center for Operational

Oceanographic Products and Services (CO-OPS), http://vdatum.noaa.gov/welcome.html. 
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