DIGITAL ELEVATION MODELS OF PUERTO RICO

noaa / NATIONAL OCEANIC AND

ATMOSPHERIC ADMINISTRATION

National Environmental Satellite,

Data, and Information Service

NOAA Technical Memorandum NESDIS NGDC- 13

DIGITAL ELEVATION MODELS OF PUERTO RICO:

PROCEDURES, DATA SOURCES AND ANALYSIS 

L.A.Taylor

B.W. Eakins

K.S. Carignan

R.R. Warnken

T. Sazonova

D.C. Schoolcraft

National Geophysical Data Center

Marine Geology and Geophysics Division

Boulder, Colorado

January 2008


DIGITAL ELEVATION MODELS OF PUERTO RICO

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-13

DIGITAL ELEVATION MODELS OF PUERTO RICO:

PROCEDURES, DATA SOURCES AND ANALYSIS

Lisa A. Taylor1

Barry W. Eakins2

Kelly S. Carignan2

Robin R. Warnken1

Tatiana Sazonova2

David C. Schoolcraft1

1

NOAA, National Geophysical Data Center, Boulder, Colorado

2

Cooperative 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 MODELS OF PUERTO RICO

Contents

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

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

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

3.1 Data Sources and Processing ......................................................................................................3

3.1.1 Shoreline................................................................................................................4

3.1.2 Bathymetry ............................................................................................................6

3.1.3 Topography..........................................................................................................14

3.2 Establishing Common Datums .................................................................................................16

3.2.1 Vertical datum transformations ...........................................................................16

3.2.2 Horizontal datum transformations.......................................................................16

3.3 Digital Elevation Model Development .....................................................................................16

3.3.1 Verifying consistency between datasets..............................................................16

3.3.2 Gridding of multibeam swath sonar data with MB-System................................17

3.3.3 Surfacing of bathymetric data .............................................................................17

3.3.4 Gridding the 1 arc-second Puerto Rico DEM .....................................................18

3.3.5 Building the 1/3 arc-second DEMs.....................................................................18

3.4 Quality Assessment of the Grids...............................................................................................19

3.4.1 Horizontal accuracy.............................................................................................19

3.4.2 Vertical accuracy .................................................................................................19

3.4.3 Slope maps and 3-D perspectives........................................................................19

3.4.4	 Comparison with source data files.......................................................................24

3.4.5 Comparison with NGS geodetic monuments......................................................24

4. Summary and Conclusions...............................................................................................................26

5. Acknowledgments............................................................................................................................26

6. References........................................................................................................................................26

7. Data Processing Software ................................................................................................................27

List of Figures

Figure 1. Overview of Puerto Rico region .................................................................................................1

Figure 2. Source and coverage of datasets used in compiling the Puerto Rico DEMs..............................3

Figure 3. Coastline datasets used in compiling the Puerto Rico DEMs.....................................................5

Figure 4. Mangrove and reef coverage along the southwest shore of Puerto Rico....................................5

Figure 5. Coverage of NOS hydrographic surveys in the Puerto Rico region ...........................................9

Figure 6. Coverage of SHOALS bathymetric LiDAR data used in compiling the Puerto Rico 

DEMs.................................................................................................................................10

Figure 7. Coverage of NOS bathymetric LiDAR surveys used in compiling the Puerto Rico 

DEMs.................................................................................................................................11

Figure 8. Source and coverage of multibeam sonar datasets used in compiling the Puerto Rico 

DEMs.................................................................................................................................13

Figure 9. Source and coverage of topographic datasets used in compiling the Puerto Rico 

DEMs.................................................................................................................................14

Figure 10. Detail of NED 1/3 arc-second DEM showing processing errors generated by USGS 

gridding algorithm .............................................................................................................15

Figure 11. Histogram of the differences between NOS hydrographic survey H09491 and the 

3 arc-second pre-surfaced bathymetric grid ......................................................................18

Figure 12. Slope map of the 1/3 arc-second Fajardo DEM........................................................................19

Figure 13. Perspective view of the 1 arc-second Puerto Rico DEM..........................................................20

Figure 14a. Color image of the 1 arc-second Puerto Rico DEM .................................................................20

Figure 14b. Color image of the 1/3 arc-second San Juan DEM...................................................................21

Figure 14c. Color image of the 1/3 arc-second Fajardo DEM.....................................................................21

Figure 14d. Color image of the 1/3 arc-second Guayama DEM..................................................................22

Figure 14e. Color image of the 1/3 arc-second Ponce DEM .......................................................................22
iv

Taylor et al., 2008

Figure 14f. Color image of the 1/3 arc-second Mayagüez DEM ................................................................23

Figure 14g. Color image of the 1/3 arc-second Arecibo DEM ....................................................................23

Figure 15. Histogram of the differences between one SHOALS bathymetric LiDAR survey and 

the Arecibo DEM...............................................................................................................24

Figure 16. Location of NGS monuments and NOAA tide stations in the Puerto Rico region. NGS 

monument elevations were used to evaluate the Puerto Rico DEMs................................25

Figure 17. Histogram of the differences between NGS monuments and the Ponce DEM ........................25

List of Tables

Table 1.	 Specifications for the Puerto Rico DEMs...................................................................................2

Table 2. Coastline datasets used in compiling the Puerto Rico DEMs.....................................................4

Table 3. Bathymetric datasets used in compiling the Puerto Rico DEMs................................................6

Table 4. Digital NOS hydrographic surveys used in compiling the Puerto Rico DEMs..........................7

Table 5. NOS hydrographic surveys included in the NCCOS bathymetric DEM....................................9

Table 6. NOS bathymetric LiDAR surveys used in compiling the Puerto Rico DEMs.........................11

Table 7. USGS multibeam sonar DEMs used in compiling the Puerto Rico DEMs..............................12

Table 8. Multibeam swath sonar data used in compiling the Puerto Rico DEMs ..................................12

Table 9. Topographic datasets used in compiling the Puerto Rico DEMs..............................................14

Table 10. Relationship between Mean High Water and other vertical datums in the Puerto Rico

 region ................................................................................................................................16

Table 11. Data hierarchy used to assign gridding weight in MB-System.................................................18


DIGITAL ELEVATION MODELS OF PUERTO RICO

Digital Elevation Models of Puerto Rico:

Procedures, Data Sources and Analysis

1. Introduction

In June 2007, the National Geophysical Data Center (NGDC), an office of the National Oceanic and Atmospheric

Administration (NOAA), developed a series of bathymetric–topographic digital elevation models (DEMs) of Puerto 

Rico (Fig. 1) for the Pacific Marine Environmental Laboratory (PMEL), NOAA Center for Tsunami Research (http://

nctr.pmel.noaa.gov/). These nested DEMs (boundaries shown in Fig. 2) will be used as input for the MOST (Method 

of Splitting Tsunami) Model developed by PMEL to simulate tsunami generation, propagation and inundation. The 

DEMs were generated from diverse digital datasets in the region (source and coverage shown in Fig. 2) and will 

be used for tsunami forecasting and modeling, as part of the tsunami forecast system, SIFT (Short-term Inundation 

Forecasting for Tsunamis). This report provides a summary of the data sources and methodology used in developing 

a 1 arc-second DEM covering the entire island of Puerto Rico and 1/3 arc-second DEMs centered on the major 

communities of Arecibo, Fajardo, Guayama, Mayagüez, Ponce and San Juan, Puerto Rico. 

Figure 1. Overview of Puerto Rico region. (image taken from http://earthquake.usgs.gov/regional/world/puerto_rico/puerto_rico_history.php)

. The Puerto Rico DEMs were built upon a grid of cells that are square in geographic coordinates (latitude and longitude), however, the cells are 

not square when converted to projected coordinate systems, such as UTM zones (in meters). At the latitude of Puerto Rico (18° N) 1/3 arc-second 

of latitude is equivalent to 10.25 meters; 1/3 arc-second of longitude equals 9.81 meters.


Taylor et al., 2008

2. Study Area

The study area covers the island of Puerto Rico, located in the Caribbean Sea, with special emphasis on the coastal 

communities at risk from tsunamis. Puerto Rico covers 8,959 square kilometers with a population of almost 4 million 

people. The DEMs that cover this region extend well offshore into deeper water for the purpose of tsunami modeling 

(Fig. 2)

The island of Puerto Rico has three main physiographic regions: mountainous interior, coastal lowlands and a 

karst region. The mountainous interior covers 60% of the island with the highest peak, Cerro La Punta, reaching 1,338 

meters. The coastal lowlands extend 13 to 19 km inward in the north and 3 to 13 km in the south. The karst region is 

located on the north side of the island.

San Juan, the capital of Puerto Rico, is located on the northeast coast and has one of the largest harbors in the 

Caribbean. San Juan covers 122 square kilometers with a population of 442,447 (2000 Census). The Bayamón River 

lies west of San Juan and empties into the Atlantic Ocean. 

The city of Fajardo is located on the east coast of Puerto Rico, covering approximately 556 square kilometers, 

with a population of 40,712 (2000 Census). Home to the largest marina in the Caribbean, Fajardo provides access to 

the Virgin Islands to the east.

Guayama, known as “La Ciudad Bruja” (witch city) or “Pueblo de los Brujos” (city of witches), is located on the 

southeastern coast of Puerto Rico, and was founded in 1736 by Matías de Abadía. Nearby is the Jobos Bay National 

Estuarine Research Reserve, established in 1987, that consists of approximately 2,883 acres of mangrove forest and 

freshwater wetlands. The areas surrounding Guayama produce sugar, tobacco, coffee, and livestock. 

Ponce is located on the southern coastal plain region of the island and has the second largest population in Puerto 

Rico. Ponce covers just over 500 square kilometers with a population of 186,475 (2000 Census). Previously a capital 

of the region for Spain, Ponce now provides a major shipping port for the Caribbean.

The city of Mayagüez is located on the west-central coast of Puerto Rico, covering 197.6 sq km, with a population 

of 104,557 (2000 Census). The Rio Grande de Añasco River lies to the north and the Guanajibo River to the south of 

Mayagüez. Both rivers empty into the Caribbean Sea from the west coast of Puerto Rico.

Arecibo, on the Puerto Rico northern coast, is home to one of the most important astronomical research facilities 

on Earth, the Arecibo Ionospheric Observatory, located in the mountains south of town. The observatory’s massive 

dish is sited in a sinkhole larger in area than a dozen football fields and is tuned to detect the slightest sounds emitted

from the farthest stars. This is the home base for NASA’s ‘SETI’ (Search for Extra-Terrestrial Intelligence) project and, 

as such, holds great fascination for visitors.

3. Methodology

The Puerto Rico DEMs were developed to meet PMEL specifications (Table 1), based on input requirements for

the MOST inundation model. The best available data were obtained by NGDC and shifted to common horizontal and 

vertical datums: World Geodetic System 1984 (WGS84) and Mean High Water (MHW), for modeling of ‘worst-case 

scenario flooding’, respectively. Data processing and evaluation, and DEM assembly and assessment are described in

the following subsections.

Table 1. Specifications for the Puerto Rico DEMs.

Grid Area Puerto Rico Arecibo Fajardo Guayama Mayagüez Ponce San Juan

Coverage Area (W)

(N)

65°–68°

17°–19o

66.5°–67.1°

18.35°–18.8°

65.35°–65.9°

18.05°–18.6°

65.7°–66.4°

17.7°–18.05°

67.1°–67.6°

17.9°–18.6°

66.4°–67.1°

17.7°–18.05°

65.9°–66.5°

18.35°–18.8°

Grid Spacing 1 arc-second 1/3 arc-second

Coordinate System Geographic decimal degrees

Horizontal Datum World Geodetic System 1984 (WGS84)

Vertical Datum Mean High Water (MHW)

Vertical Units Meters

Grid Format ESRI ASCII raster grid
DIGITAL ELEVATION MODELS OF PUERTO RICO

3.1 Data Sources and Processing

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

and state government agencies, and universities, including: the U.S. Geological Survey (USGS); the NOAA National 

Ocean Service (NOS), National Geodetic Survey (NGS), Office of Coast Survey (OCS) and National Centers for

Coastal Ocean Science (NCOOS); the Puerto Rico Planning Board (PRPB); the Puerto Rico Office of Management

and Budget; and the University of Puerto Rico. Safe Software’s (http://www.safe.com/) FME data translation tool 

package was used to shift datasets to WGS84 horizontal datum and to convert into ESRI (http://www.esri.com/) 

ArcGIS shape files. The shape files were then displayed with ArcGIS to assess data quality and manually edit datasets.

NGDC’s GEODAS software (http://www.ngdc.noaa.gov/mgg/geodas/) was used to manually edit large xyz datasets. 

Quick Terrain Modeler (http://www.appliedimagery.com/) was used to evaluate and edit the NOS bathymetric LiDAR 

surveys. Vertical datum transformations to MHW were accomplished using FME, based upon data from NOAA tide 

stations at San Juan and Magueyes Island (http://tidesandcurrents.noaa.gov/). VDatum (http://nauticalcharts.noaa.

gov/csdl/vdatum.htm) was not available for this area.

Figure 2. Source and coverage of datasets used in compiling the Puerto Rico DEMs (boundaries in red).
Taylor et al., 2008

3.1.1 Shoreline

Digital shorelines were obtained from the Puerto Rico Planning Board and the National Oceanic and Atmospheric 

Administration (Table 2). The differences between the coastlines are largely qualitative and are due mainly to mangrove 

swamps portrayed as either landward or seaward of the coastline. As areas of dense mangrove coverage are known to 

strongly dissipate tsunami energy, it is important to make the distinction as to where the coastline lies relative to these 

areas. 

Table 2: Coastline datasets used in compiling the Puerto Rico DEMs.

Source Area Description URL

Puerto Rico Planning Board Island of 

Puerto Rico Digitized from aerial photos http://www.crimpr.net/

NOAA National Geodetic 

Survey

Culebra, 

Vieques and 

other islands

Digitized NOS shoreline maps http://www.csc.noaa.gov/shoreline/data.html

NOAA Office of Coast Survey

Mona and 

Desecheo 

islands

Extracted from NOS nautical 

charts http://nauticalcharts.noaa.gov/csdl/ctp/cm_vs.htm

1) Puerto Rico Planning Board digitized coastline of the main island of Puerto Rico

This coastline was provided to NGDC by Dewberry and Davis, Inc. It was digitized by the Puerto 

Rico Planning Board (PRPB) from 1995 aerial photos as part of the “Centro de Recaudación de Ingresos 

Municipales (CRIM), Land Information System Project” between 1996 and 1998. Dewberry and Davis, 

Inc. received the coastline in multiple pieces, by USGS quadrangle, which they merged together and 

checked against orthometric photographs for accuracy. It was also degraded from a scale of 1:2,000 to 

1:5,000.

2) Vectorized shoreline derived from NOS shoreline maps

This shoreline dataset represents a vector conversion of NOS shoreline (T-sheets) maps and CADbased Standard Digital Data Exchange Format (SDDEF) data. It was created by the NOAA National 

Geodetic Survey (NGS) as part of its ongoing mission to map the coastline of the United States. The 

NOAA Coastal Services Center developed the procedures used in this project and was responsible for 

project oversight. 

3) NOS nautical charts extracted vector shoreline

This coastline was extracted from NOS nautical charts using software developed by the NOAA 

Office of Coast Survey, Coast Survey Development Laboratory, Cartographic & Geospatial Technology

Program. It is referenced to mean high water, NAD83 in non-projected geographic coordinates and 

based on 1:10,000 to 1:80,000 scale charts.

After analysis of the available coastlines, the vector shoreline generated from orthometric photos by the Puerto 

Rico Planning Board obtained from Dewberry and Davis, Inc, was chosen for the main island. Surrounding islands 

were added from the NOAA, NOS, OCS Extracted Vector Shoreline and the NOAA, NOS Digitized Coastline using 

ESRI ArcEdit. This “combined coastline” (Fig. 3) defines the mangrove-sea interface, encompassing mangrove areas

around the island, except for the La Parguera area between 66.98o and 67.13o west (Fig. 4). The combined coastline 

was converted to point data for use as a coastal buffer for the bathymetric pre-surfacing algorithm (see Section 3.3.2) 

to ensure that interpolated bathymetric values reached “zero” at the coast. It was also provided to the U.S. Geological 

Survey for their use in developing a 1/3 arc-second National Elevation Dataset (NED) DEM for Puerto Rico (see 

Section 3.1.3).
DIGITAL ELEVATION MODELS OF PUERTO RICO

Figure 3. Coastline datasets used in compiling the Puerto Rico DEMs. PRPB coastline (blue); NOS 

shoreline maps (red); and NOS nautical charts (green).

Figure 4. Mangrove and reef coverage along the southwest shore of Puerto Rico. The green box represents the Parguera 

mangrove area, which is not encompassed by the PRPB coastline. This area is characterized by an extensive development 

of coral reefs, seagrass beds, and mangrove forests. (Graphic from NCCOS Biogeography Program, 2001)
Taylor et al., 2008

3.1.2 Bathymetry

Bathymetric datasets used in the compilation of the Puerto Rico DEMs (Table 3) included: 114 NOS hydrographic 

surveys; seven NOS bathymetric LiDAR surveys; U.S. Army Corps of Engineers SHOALS coastal LiDAR surveys; 

a 5 meter cell-size bathymetric DEM derived from NOS hydrographic survey data and scuba depths off the southwest 

coast of the island of Puerto Rico; DEMs derived from deep water multibeam sonar surveys collected by the U.S. 

Geological Survey; multibeam swath sonar files archived at NGDC and Lamont Doherty Earth Observatory; and a

9 arc-second DEM compiled from seafloor predicted topography data and General Bathymetric Chart of the Oceans

(GEBCO) bathymetric contours.

Table 3. Bathymetric datasets used in compiling the Puerto Rico DEMs.

Source Year Data Type Spatial Resolution Original Horizontal 

Datum

Original 

Vertical 

Datum

URL

NOS 1900 to 

2001

Hydrographic 

survey soundings

Ranges from 10 meters to 

3 kilometers (Varies with 

scale of survey, depth, 

traffic and probability of

obstructions)

Early Puerto Rico 

Island Datum, Puerto 

Rico Datum, NAD27 

geographic, NAD83 

geographic

MLW, 

MLLW

http://www.ngdc.noaa.

gov/mgg/bathymetry/

hydro.html

NCCOS 2004

DEM of NOS 

soundings and 

scuba depths

5 meter DEM WGS84 geographic MLLW http://coastalscience.

noaa.gov/

JALBTCX 2001

SHOALS 

bathymetric 

LiDAR

5 meter posting

NAD83 US Virgin 

Islands, Puerto Rico 

State Plane

MLLW

NOS 2006 bathymetric 

LiDAR 1 meter posting NAD83 UTM Zone 19 MLLW

USGS 2004–

2007

DEMs of 

multibeam sonar 

surveys

1 to 5 arc-seconds NAD83 UTM Zone 19 MSL

NGDC, 

LDEO

1985–

2005

Multibeam swath 

sonar files Varies with depth WGS84 geographic MSL

http://www.ngdc.noaa.

gov/mgg/bathymetry/

multibeam.html and 

http://www.marinegeo.org/

NGDC 2005

DEM of Smith 

and Sandwell 

Predicted 

Topography 

combined with 

GEBCO contours.

9 arc-second WGS84 geographic MSL

http://topex.ucsd.edu/

marine_topo/ and

http://www.bodc.

ac.uk/projects/

international/gebco/

gebco_digital_atlas/

gda_development/

1) NOS hydrographic surveys

A total of 114 NOS hydrographic surveys were used in building the Puerto Rico DEMs (Table 4; Fig. 

5). The survey data were originally vertically referenced to either mean lower low water or mean low 

water and horizontally referenced to Early Puerto Rico datum, Puerto Rico datum, NAD27 geographic 

and NAD83 geographic. Data point spacing for the surveys ranges from about 10 meters in shallow to 

up to 3 kilometers in deep water. 
DIGITAL ELEVATION MODELS OF PUERTO RICO

Table 4. Digital NOS hydrographic surveys used in compiling the Puerto Rico DEMs.

NOS Survey ID Year of Survey Survey Scale Original Vertical Datum Original Horizontal Datum

F00279 1985 1:5,000 MLLW Puerto Rico Datum

H02468 1904 1:5,000 MLW Early PR Island Datums

H02469 1900 1:10,000 MLW Early PR Island Datums

H02472 1900 1:5,000 MLW Early PR Island Datums

H02490 1909 1:40,000 MLW Early PR Island Datums

H02491 1909 1:10,000 MLW Early PR Island Datums

H02492 1905 1:10,000 MLW Early PR Island Datums

H02536 1901 1:20,000 MLW Early PR Island Datums

H02537 1901 1:20,000 MLW Early PR Island Datums

H02555 1902 1:10,000 MLW Early PR Island Datums

H02582 1905 1:20,000 MLW Early PR Island Datums

H02584 1902 1:20,000 MLW Early PR Island Datums

H02585 1902 1:10,000 MLW Early PR Island Datums

H02633 1903 1:20,000 MLW Early PR Island Datums

H02634 1903 1:20,000 MLW Early PR Island Datums

H02640 1903 1:40,000 MLW Early PR Island Datums

H02672 1904 1:40,000 MLW Early PR Island Datums

H02673 1904 1:20,000 MLW Early PR Island Datums

H02674 1904 1:20,000 MLW Early PR Island Datums

H02676 1909 1:60,000 MLW Early PR Island Datums

H02677 1904 1:20,000 MLW Early PR Island Datums

H02678 1904 1:20,000 MLW Early PR Island Datums

H02686 1904 1:10,000 MLW Early PR Island Datums

H02690 1904 1:10,000 MLW Early PR Island Datums

H02803 1906 1:40,000 MLW Early PR Island Datums

H02804 1906 1:20,000 MLW Early PR Island Datums

H02871 1907 1:20,000 MLW Early PR Island Datums

H02876 1909 1:20,000 MLW Early PR Island Datums

H02877 1909 1:20,000 MLW Early PR Island Datums

H02883 1907 1:20,000 MLW Early PR Island Datums

H02934 1908 1:20,000 MLW Early PR Island Datums

H02935 1908 1:20,000 MLW Early PR Island Datums

H02936 1908 1:20,000 MLW Early PR Island Datums

H02937 1908 1:20,000 MLW Early PR Island Datums

H02938 1908 1:20,000 MLW Early PR Island Datums

H03004 1909 1:20,000 MLW Early PR Island Datums

H04205 1921 1:20,000 MLW Early PR Island Datums

H04725 1927 1:10,000 MLW Early PR Island Datums

H04742 1927 1:10,000 MLW Early PR Island Datums

H06556 1940 1:10,000 MLW Early PR Island Datums

H08637 1962 1:10,000 MLW Puerto Rico Datum

H08638 1962 1:10,000 MLW Puerto Rico Datum

H08639 1969 1:5,000 MLW Early PR Island Datums

H08780 1967 1:20,000 MLW Early PR Island Datums

H08811 1964 1:10,000 MLW Puerto Rico Datum

H08812 1967 1:20,000 MLW Puerto Rico Datum

H08813 1964 1:5,000 MLW Puerto Rico Datum

H08814 1964/65 1:10,000 MLW Early PR Island Datums

H08848 1965 1:5,000 MLW Puerto Rico Datum

H08849 1965 1:5,000 MLW Puerto Rico Datum

H08862 1965 1:5,000 MLW Early PR Island Datums

H08877 1966 1:5,000 MLW Early PR Island Datums

H08880 1966 1:20,000 MLW Early PR Island Datums

H08985 1968 1:10,000 MLW Early PR Island Datums

H08986 1968 1:10,000 MLW Early PR Island Datums

H08987 1968 1:10,000 MLW Early PR Island Datums

H08988 1968 1:10,000 MLW Puerto Rico Datum
Taylor et al., 2008

H0898919681:20,000 MLW Early PR Island Datums

H0902919691:100,000 MLW Early PR Island Datums

H0903

119691:5,000 MLW Puerto Rico Datum

H0903219691:5,000 MLW Early PR Island Datums

H090331969

1:20,000 MLW Early PR Island Datums

H0903419691:20,000 MLW Early PR Island Datums

H0911019701:5,000 MLW Early PR Island Datums

H0911

919701:10,000 MLW Early PR Island Datums

H0912019701:5,000 MLW Early PR Island Datums

H09

1351970/711:10,000 MLW Early PR Island Datums

H0918319711:10,000 MLW Early PR Island Datums

H0918619711:10,000 MLW Early PR Island Datums

H09

19019711:10,000 MLW Early PR Island Datums

H0926419721:10,000 MLW Early PR Island Datums

H09

26519721:10,000 MLW Early PR Island Datums

H0926619721:20,000 MLW Early PR Island Datums

H092671972/751:10,000 MLW Early PR Island Datums

H09

27019671:40,000 MLW NAD27 geographic

H0927119721:10,000 MLW Early PR Island Datums

H09

27219721:10,000 MLW Early PR Island Datums

H09

27319721:20,000 MLW Early PR Island Datums

H09

27819721:100,000 MLW Early PR Island Datums

H0946319751:125,000 MLW Early PR Island Datums

H0948519751:10,000 MLW Early PR Island Datums

H094861975

1:20,000 MLW Early PR Island Datums

H0949019751:5,000 MLW Early PR Island Datums

H0949119751:5,000 MLW Early PR Island Datums

H095

1719751:20,000 MLW Early PR Island Datums

H0958719761:125,000 MLW Early PR Island Datums

H095951976

1:100,000 MLW Early PR Island Datums

H0959619761:10,000 MLW Early PR Island Datums

H0959719761:10,000 MLW Early PR Island Datums

H0960119761:10,000 MLW Early PR Island Datums

H0960219761:10,000 MLW Early PR Island Datums

H0960319761:10,000 MLW Early PR Island Datums

H0960419761:20,000 MLW Early PR Island Datums

H0960519761:20,000 MLW Early PR Island Datums

H096071976

1:10,000 MLW Early PR Island Datums

H0960819761:10,000 MLW Early PR Island Datums

H096091976

1:5,000 MLW Early PR Island Datums

H0961019761:20,000 MLW Early PR Island Datums

H096

1619761:10,000 MLW Early PR Island Datums

H096

1719761:10,000 MLW Early PR Island Datums

H096

1819761:20,000 MLW Early PR Island Datums

H0999

219821:80,000 MLW Early PR Island Datums

H0999319821:80,000 MLW Early PR Island Datums

H1007319831:10,000 MLLW Puerto Rico Datum

H1007419831:80,000 MLLW Puerto Rico Datum

H1007619831:80,000 MLLW Puerto R

ico Datum

H1007719831:10,000 MLLW Puerto R

ico Datum

H1007819831:20,000 MLLW NAD27 geographic

H1008319831:80,000 MLLW Puerto Rico Datum

H1050519931:5,000 MLLW NAD83 geographic

H1050619931:5,000 MLLW NAD83 geograph

ic

H1103320011:5,000 MLLW NAD83 geograph

ic

H1103420011:5,000 MLLW NAD83 geographic

H1103620011:5,000 MLLW NAD83 geographic
DIGITAL ELEVATION MODELS OF PUERTO RICO

Figure 5. Coverage of NOS hydrographic surveys in the Puerto Rico region. DEM boundaries in red.

2) NOAA National Centers for Coastal Ocean Science (NCCOS) DEM

NOAA’s National Ocean Service (NOS), National Centers for Coastal Ocean Science (NCCOS), 

Biogeography Team provided a 5-meter bathymetric DEM derived from NOS hydrographic surveys 

(Table 5) and depths collected by Biogeography Team SCUBA divers. SCUBA depths were used to fill

gaps inshore of the NOS survey data. The DEM was generated using a triangulated interpolated network 

(TIN) with ESRI ArcView® 3D Analyst software. All reef crests were given a depth of 0.3 meters. Model 

validation using an independent set of bathymetric data revealed an average error of less than 0.3 meters. 

TIN models were then converted into raster maps (spatial resolution = 5 x 5 m). After conversion of this 

grid to MHW and WGS84, depth values were compared to NOS hydrographic survey and SHOALS 

LiDAR data in the same area and were within ~ 0.5 meters in most areas. 

Table 5. NOS hydrographic surveys included in the NCCOS bathymetric DEM.

NOS Survey ID Year of Survey Survey Scale Original Vertical Datum Original Horizontal Datum

H02676 1909 1:60,000 MLW Early PR Island Datums

H08984 1968 1:10,000 MLW Early PR Island Datums

H08985 1968/69 1:10,000 MLW Early PR Island Datums

H08986 1968 1:10,000 MLW Early PR Island Datums

H08987 1968 1:10,000 MLW Early PR Island Datums

H08988 1968 1:10,000 MLW Puerto Rico Datum

H08989 1968 1:20,000 MLW Early PR Island Datums

H09029 1969 1:100,000 MLW Early PR Island Datums

H09033 1969 1:20,000 MLW Early PR Island Datums

H09119 1970 1:10,000 MLW Early PR Island Datums

H09120 1970 1:5,000 MLW Early PR Island Datums

H09183 1971 1:10,000 MLW Early PR Island Datums
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Taylor et al., 2008

3) SHOALS LiDAR data

Dr. Aurelio Mercado-Irizarry at the University of Puerto Rico provided NGDC with bathymetric 

SHOALS LiDAR data collected by the Joint Airborne LiDAR Bathymetry Technical Center of Expertise 

(JALBTCX). The 2001 survey encircles the islands of Culebra and Vieques, and most of Puerto Rico, 

except its southern coast. Data coverage spans from the shoreline to several kilometers offshore at 5 

meter spacing (Fig. 6). The data were positioned using post-processed kinematic GPS and National 

Geodetic Survey monuments.

Figure 6. Coverage of SHOALS bathymetric LiDAR data used in compiling the Puerto Rico DEMs.

. These data were collected by the SHOALS (Scanning Hydrographic Operational Airborne Lidar Survey) system, which consists of an airborne 

laser transmitter/receiver capable of measuring 400 soundings per second. The system operates from a deHavilland DHC-6 Twin Otter flying at

altitudes between 200 and 400 meters with a ground speed of about 100 knots. The SHOALS system also includes a ground-based data processing 

system for calculating acurate horizontal position and water depth. Lidar is an acronym for LIght Detection And Ranging. The system operates by 

emitting a pulse of light that travels from an airborne platform to the water surface where a small portion of the laser energy is backscattered to the 

airborne receiver. The remaining energy at the water’s surface propogates through the water column and reflects off the sea bottom and back to the

airborne detector. The time difference between the surface return and the bottom return corresponds to water depth. The maximum depth the system 

is able to sense is related to the complex interaction of radiance of bottom material, incident sun angle and intensity, and the type and quantity of 

organics or sediments in the water column. As a rule-of-thumb, the SHOALS system should be capable of sensing bottom to depths equal to two or 

three times the Secchi depth. [Extracted from metadata.]
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DIGITAL ELEVATION MODELS OF PUERTO RICO

4) NOS LiDAR bathymetry

In 2006 NOS conducted bathymetric LiDAR surveys covering the southwestern portion of Puerto 

Rico (Table 6; Fig. 7). Data collection was conducted using the LADS Mk II Airborne System, data 

processing using the LADS Mk II Ground System and data visualization, quality control and final

products using CARIS (http://www.caris.com/). Most of the survey data have been archived at NGDC 

in UTM Zone 19 and MLLW datums, with soundings extracted using CARIS software; four surveys 

have not been processed to date. The data were subsequently evaluated and edited with QT Modeler, and 

transformed to WGS84 and MHW using FME software. 

Table 6. NOS bathymetric LIDAR surveys used in compiling the Puerto Rico DEMs.

NOS Survey ID Year of Survey Survey Scale Original Vertical Datum Original Horizontal Datum

H11557 2006 1:10,000 MLLW NAD83 UTM Zone 19

H11558 2006 1:10,000 MLLW NAD83 UTM Zone 19

H11559 2006 1:10,000 MLLW NAD83 UTM Zone 19

H11563 2006 1:10,000 MLLW NAD83 UTM Zone 19

H11565 2006 1:10,000 MLLW NAD83 UTM Zone 19

H11566 2006 1:10,000 MLLW NAD83 UTM Zone 19

H11567 2006 1:10,000 MLLW NAD83 UTM Zone 19

Figure 7. Coverage of NOS bathymetric LiDAR surveys used in compiling the Puerto Rico DEMs.
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Taylor et al., 2008

5) DEMs of USGS multibeam swath sonar surveys

Uri ten Brink and Jason Chaytor with the U.S. Geological Survey provided NGDC with DEMs 

of proprietary multibeam swath sonar surveys that their team has recently conducted around Puerto 

Rico (Table 7; Fig. 8). DEMs were referenced to NAD83 UTM Zone 19 and MSL. NGDC resampled 

the 5 arc-second DEMs to 3 arc-seconds, using ArcGIS, for use in building a preliminary 3 arc-second 

bathymetric surface (see Section 3.3.3). See ten Brink and Smith (2003), ten Brink, et al. (2004), and 

Carbó et al. (2005) for details on research discoveries related to these surveys.

Table 7. USGS multibeam sonar DEMs used in compiling the Puerto Rico DEMs.

DEM ID Year of Survey Cell Size Vessel

HE-05019 2005 5 arc-seconds Hesperis

NF0704 2007 1 arc-second Nancy Foster

RB0604 2006 5 arc-seconds Ron Brown

RB0605 2006 5 arc-seconds Ron Brown

6) Multibeam swath sonar surveys 

The original sonar files from multibeam swath sonar surveys and transits in the Puerto Rico region

(Table 8; Fig. 8) were downloaded from the NGDC multibeam database (http://www.ngdc.noaa.gov/

mgg/bathymetry/multibeam.html) and from the Marine Geoscience Data System database (Carbotte, 

et al., 2004; http://www.marine-geo.org/). All sonar data were in WGS84 and MSL datums. Data were 

processed, evaluated, and edited using the MB-System software package (http://www.ldeo.columbia.edu/

res/pi/MB-System/), an NSF-funded share-ware software application specifically designed to manipulate

multibeam sonar data. Several cruises (C2907, EW9706, EW0105 and EW0301) had frequent anomalous 

values and showed significant discrepancies with other cruises, the USGS multibeam sonar DEMs and

NOS hydrographic surveys: these cruises were not used in building the Puerto Rico DEMs. 

Table 8. Multibeam swath sonar data used in compiling the Puerto Rico DEMs.

Cruise ID Year of Survey Source Vessel Sonar System Cruise Type

AT04L04 2001 NGDC Atlantis SeaBeam 2100 Transit

C2605 1985 NGDC Conrad SeaBeam Transit

EW9501 1995 MGDS Ewing Atlas Hydrosweep Transit

EW9605 1996 MGDS Ewing Atlas Hydrosweep Transit

EW0102 2001 MGDS Ewing Atlas Hydrosweep Transit

EW0103 2001 MGDS Ewing Atlas Hydrosweep Transit

EW0106 2001 MGDS Ewing Atlas Hydrosweep Transit

EW0302 2003 NGDC Ewing Atlas Hydrosweep Transit

EW0309 2003 MGDS Ewing Atlas Hydrosweep Transit

EW0403 2004 NGDC Ewing Atlas Hydrosweep Transit

EW0404 2004 MGDS Ewing Atlas Hydrosweep Transit

EW0405 2004 NGDC Ewing Atlas Hydrosweep Transit

HLY-05-TH 2005 MGDS Healy SeaBeam 2112 Transit

KN151L4 1997 NGDC Knorr SeaBeam 2100 Transit

KN161L07 2000 MGDS Knorr SeaBeam 2100 Transit

KN173L02 2003 NGDC Knorr SeaBeam 2100 Transit

RB0208 2002 NGDC Ron Brown SeaBeam 2112 Puerto Rico Trench survey

RB0303 2003 NGDC Ron Brown SeaBeam 2112 Puerto Rico Trench survey
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DIGITAL ELEVATION MODELS OF PUERTO RICO

Figure 8. Source and coverage of multibeam sonar datasets used in compiling the Puerto Rico DEMs.

7) 9 arc-second DEM

No detailed bathymetric datasets were available for the southeast corner of the Puerto Rico region 

(see Fig. 2). Thus, depth values were extracted from an intermediate 9 arc-second DEM that NGDC built 

in 2005—compiled from the ‘Measured and Estimated Seafloor Topography’ 2-minute DEM (Smith and

Sandwell, 1997; http://topex.ucsd.edu/WWW_html/mar_topo.html) and GEBCO bathymetric contours 

(http://www.ngdc.noaa.gov/mgg/gebco/).
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Taylor et al., 2008

3.1.3 Topography

Two topographic datasets of PuertoRico (Table 9; Fig. 9) were obtained fromthe PuertoRico Office ofManagement

and Budget and the U.S. Geological Survey, and were used in building the Puerto Rico DEMs.

Table 9. Topographic datasets used in compiling the Puerto Rico DEMs.

Source Year Data Type Spatial 

Resolution

Original Horizontal 

Datum

Original 

Vertical 

Datum

URL for more info

Puerto Rico Office

of Management and 

Budget

1996–1998

Photometrically 

derived 

elevations

10 meters

NAD83 HARN US 

Virgin Islands, Puerto 

Rico State Plane

NAVD88 

(MSL) http://www.crimpr.net/

USGS 2007

National 

Elevation 

Dataset (NED)

1/3 arcsecond WGS84 geographic GEOID99? http://seamless.usgs.gov/

Figure 9. Source and coverage of topographic datasets used in compiling the Puerto Rico DEMs.

1) Puerto Rico Office of Management and Budget photometrically derived elevations

DEMs of photometrically derived elevations over USGS Quadrangles in Puerto Rico, with fixed spatial

cell size of 10 meters, was obtained from the Puerto Rico Office of Management and Budget (PROMB). The

Centro de Recaudación de Ingresos Municipales (CRIM) Basemap Project provided the original linework, 

elevation points and breaklines to PROMB. PROMB derived the DEMs from TINs previously generated 

from elevation mass points and 3-D features such as hydrography, and breaklines at a scale of 1:2,000. 

Elevation values are referenced to mean sea level. This dataset covers Puerto Rico and Culebra islands and 

the western half of Vieques (Fig. 9).
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DIGITAL ELEVATION MODELS OF PUERTO RICO

2) USGS NED 1/3 arc-second DEM

A newly created National Elevation Dataset (NED)3 1/3 arc-second DEM of Puerto Rico was provided to 

NGDC by Louis Driber and Charles Nelson with the USGS. This topographic DEM was derived principally 

from LiDAR data collected by 3001, Inc. for the USACE in 2004 as part of an effort to develop digital 

orthophoto imagery for administration of the U.S. Department of Agriculture GIS Orthophotography update 

program. The DEM also included supplemental LiDAR data collected by the USGS. The NED DEM was 

built by gridding the LiDAR data in USGS quadrangle quarters using TINs (triangular irregular networks), 

then mosaicing the grids together. No data buffers were utilized along the edges of quadrangle quarters, 

which resulted in the gridding process connecting the corners of some quadrangle quarters with triangles of 

anomalous elevations. These anomalous triangles occur where LiDAR data gaps fall in regions of steep of 

topography (mostly interior of the Island of Puerto Rico at high elevations) and along quadrangle quarter 

boundaries (e.g., Fig. 10). NGDC could not remove these “seams”, which remain in the Puerto Rico DEMs. 

The NED DEM appears to be referenced to GEOID99 over the islands of Puerto Rico, Vieques and 

Culebra as substantial parts of the coastal zone are below MHW; the metadata documents the DEM as being 

referenced to “NAVD88”, which is not a valid vertical datum for Puerto Rico. GEOID99 is on average 2.29 

meters below MSL along the north side of the Island of Puerto Rico (Dave Doyle, NGS, pers. communication), 

likely contributing to the anomalous “underwater” land areas in the DEM. Also apparent in the NED DEM 

are shifts in the coastline north of Fajardo, and artificial flat regions along the southern coast. The islands

of Mona and Desecheo are consistent with a mean sea level datum. NGDC used this dataset only where the 

PROMB DEMs were unavailable.

Figure 10. Detail of NED 1/3 arc-second DEM showing processing errors generated by USGS gridding algorithm.

3. The USGS National Elevation Dataset (NED) has been developed by merging the highest-resolution, best quality elevation data available across 

the United States into a seamless raster format. NED is the result of the maturation of the USGS effort to provide 1:24,000-scale Digital Elevation 

Model (DEM) data for the conterminous U.S. and 1:63,360-scale DEM data for Georgia. The dataset provides seamless coverage of the United 

States, HI, AK, and the island territories. NED has a consistent projection (Geographic), resolution (1 arc second), and elevation units (meters). The 

horizontal datum is NAD83, except for AK, which is NAD27. The vertical datum is NAVD88, except for AK, which is NGVD29. NED is a living 

dataset that is updated bimonthly to incorporate the “best available” DEM data. As more 1/3 arc second (10 m) data covers the U.S., then this will 

also be a seamless dataset. [Extracted from USGS NED website]
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Taylor et al., 2008

3.2 Establishing Common Datums

3.2.1 Vertical datum transformations

Datasets used in the compilation and evaluation of the Puerto Rico DEMs were originally referenced to a number 

of vertical datums including Mean Lower Low Water (MLLW), Mean Low Water (MLW), Mean Sea Level (MSL), 

and North American Vertical Datum of 1988 (NAVD88). All datasets were transformed to MHW, to provide the worstcase scenario for inundation modeling, by averaging tidal values measured at the NOAA tidal stations at San Juan 

(#9755371) and Magueyes Island (#9759110).

1) Bathymetric data

The NOS hydrographic soundings, and SHOALS and NOS LiDAR surveys were transformed from MLW 

and MLLW to MHW, using FME software, by adding constant offsets of -0.270 and -0.300 m, respectively 

(Table 10). The USGS multibeam sonar DEMs and multibeam swath sonar data are referenced to MSL and 

were shifted by adding a constant offset of -0.132 m. 

2) Topographic data

The PROMB DEMs were referenced to MSL. USGS NED 1/3 arc-second DEM was referenced to 

NAVD88 in its metadata, which is not defined for Puerto Rico: this dataset was inferred to be referenced to

MSL. Conversion to MHW, using FME software, was accomplished by adding tide-station derived constant 

offset of -0.132 (Table 10). 

Table 10. Relationship between Mean High Water and other vertical datums in the Puerto Rico region.*

Vertical datum Difference to MHW

MSL+ -0.132

MLW -0.270

MLLW -0.300

* Datum relationships averaged from values at tide stations #9755371, San Juan and #9759110, Magueyes Island.

+ NAVD88 is inferred to be equivalent to MSL.

3.2.2 Horizontal datum transformations

Datasets used to compile the grids were originally horizontally referenced to Puerto Rico and Virgin Islands State 

Plane, Early Puerto Rico Island Datum, Puerto Rico Datum, NAD83 UTM Zone 19, and NAD27, NAD83 and WGS84 

geographic; the relationships and transformational equations between these horizontal datums are well established. 

NOS hydrographic survey data was converted to WGS84 using GEODAS (NADCON). All other data were converted 

to a horizontal datum of WGS84 using FME software (http://www.safe.com). FME is an integrated collection of 

spatial extract, transform, and load tools for data transformation and data translation.

3.3 Digital Elevation Model Development

3.3.1 Verifying consistency between datasets.

After horizontal and vertical transformations were applied, ESRI shape files were generated for each data file, and

value consistency between datasets was checked in ESRI ArcMap. Problems and errors were identified and resolved

before proceeding with subsequent gridding steps. The evaluated and edited ESRI shape files were then converted to

xyz files in preparation for gridding. Problems included:

•	 The USGS NED 1/3 arc-second DEM for Puerto Rico includes “seams” along the edges of quadrangle 

quarters in regions of steep topography (island interior at high elevations). NGDC could not remove these 

gridding artifacts. 

•	 Vertical units for the NCCOS bathymetric DEM was determined to be feet instead of meters, as indicated in 

the accompanying metadata. The DEM was converted to meters before gridding.

•	 A few bad soundings were discovered in the NOS hydrographic surveys (positive values rather than negative 

ones) and were corrected. Several NOS surveys had mixed units of feet and fathoms, which also had to be 

corrected.
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DIGITAL ELEVATION MODELS OF PUERTO RICO

•	 The SHOALS bathymetric LiDAR data included positive elevations that were deleted. They also included 

occasional anomalously deep values along the coast, which were deleted.

•	 Numerous bad sonar pings and beams were identified in the raw multibeam swath sonar data. These pings

and beams were excised from the data prior to gridding, using the MB-System tool ‘mbedit’. Some transits 

were exceptionally noisy on their outer beams, which were removed using the automated MB-System tool 

‘mbclean’.

•	 The USGS multibeam sonar bathymetric DEMs contained some cells with anomalous values. These were 

deleted once the DEMs had been converted to ESRI point shapefiles.

•	 The USGS NED 1/3 arc-second topographic DEM was found to be low by a meter or two along most coasts 

in the Puerto Rico region. This is inferred to result from the GEOID99 model for Puerto Rico, which is low 

by ~2.29 meters along the northern coast of the Island of Puerto Rico.

•	 The PROMB topographic DEMs contained “zero” values over the open ocean, and anomalous values along 

the edges of DEMs. These values were deleted.

3.3.2 Gridding of multibeam swath sonar data with MB-System

The raw multibeam sonar filesfrom transitsin the Puerto Rico region (Table 8) were gridded using the MB-System

tool ‘mbgrid’ at 3 arc-second resolution covering a region 0.1 degrees larger than the Puerto Rico DEM; deep-water 

sonars generally provide between 30 and 150-meter beam footprints depending upon water depth. A short interpolation 

spacing of 2 grid cells was used to infill small gaps between beams while limiting interpolation into regions without

sonar coverage. Sonar data that was exceptionally noisy or diverged significantly from other bathymetric datasets was

either edited or discarded. The resulting 3 arc-second grid was brought into ArcGIS for evaluation, then converted to 

ESRI point shapefile for editing. Points were deleted where coverage of the “transit” multibeam sonar grid overlapped

the USGS multibeam sonar grids (dedicated seafloor surveys; Table 7). The multibeam swath sonar files from the two

Puerto Rico Trench surveys (RB0208 and RB0303; Table 8) were gridded separately at 1 arc-second as they were 

deemed to be of high quality.

3.3.3 Surfacing of bathymetric data

The NOS hydrographic surveys are generally sparse at the resolution of the Puerto Rico DEMs: in deep water, the 

NOS survey data have point spacings up to 3 km apart. In order to reduce the effect of artifacts in the form of lines of 

“pimples” in the DEMs due to this low resolution dataset, and to provide effective interpolation into the coastal zone, a 

3 arc-second-spacing ‘pre-surface’ or grid was generated using GMT, an NSF-funded share-ware software application 

designed to manipulate data for mapping purposes (http://gmt.soest.hawaii.edu/). NOS soundings that overlapped 

the multibeam sonar grids were deleted as the resolution of the NOS surveys was significantly less than that of the

multibeam sonar data.

The remaining NOS hydrographic point data, in xyz format, were combined with xyz data from the multibeam 

sonar and NCCOS grids, and bathymetric LiDAR surveys into a single file, along with points extracted from the

combined coastline—to provide a “zero” buffer along the entire coastline. These point data were then median-averaged 

using the GMT tool ‘blockmedian’ to create a 3 arc-second grid 0.1 degrees (~10%) larger than the Puerto Rico 

DEM gridding region. The GMT tool ‘surface’ then applied a spline tension to interpolate cells without data values. 

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

eliminate data interpolation into land areas. The resulting surface was compared with original soundings to ensure grid 

accuracy (e.g., Fig. 11), converted to a shape file, and then exported as an xyz file for use in the final gridding process

(see Table 11). 
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Taylor et al., 2008

Figure 11. Histogram of the differences between NOS hydrographic survey H09491 (Bahia de Jobos, south coast) and 

the 3 arc-second pre-surfaced bathymetric grid. Large discrepancies between survey soundings and the pre-surface 

bathymetric grid occur where multiple, closely spaced points, in regions with significant relief, contribute to one cell value.

3.3.4 Gridding the 1 arc-second Puerto Rico DEM

All processed xyz data files were gridded at 1 arc-second using MB-System (http://www.ldeo.columbia.edu/res/

pi/MB-System/). The MB-System tool ‘mbgrid’ was used to create each DEM—a modeled surface draping the point 

data—comprised of weighted elevation point data. The data hierarchy used in the ‘mbgrid’ gridding algorithm as 

relative gridding weights is listed in Table 11. Greatest weight was given to the NOS and SHOALS coastal bathymetric 

LiDAR data. Least weight was given to values extracted from the 3 arc-second bathymetric grid.

Table 11. Data hierarchy used to assign gridding weight in MB-System.

Dataset Relative Gridding Weight

NOS bathymetric LiDAR surveys 1000

SHOALS bathymetric LiDAR 100

1 arc-second multibeam sonar bathymetric grids 100

PROMB topographic DEMs 100

USGS NED topographic DEM 10

NOS hydrographic surveys 1

NCCOS bathymetric DEM 1

3 arc-second pre-surfaced bathymetric grid* 0.1

1 arc-second Puerto Rico DEM+ 0.1

* Used only for building the 1 arc-second Puerto Rico DEM.

+ Used only for building the 1/3 arc-second DEMs.

3.3.5 Building the 1/3 arc-second DEMs

The 1/3 arc-second DEMs were built using all of the processed xyz files and points extracted from the 1 arcsecond Puerto Rico DEM, using MB-System. The MB-System tool ‘mbgrid’ was used to create each DEM, comprised 

of weighted elevation point data. The data hierarchy used in the ‘mbgrid’ gridding algorithm as relative gridding 

weights is listed in Table 11. Greatest weight was given to the NOS and SHOALS coastal bathymetric LiDAR data. 

Least weight was given to values extracted from the 1 arc-second Puerto Rico DEM.
19

DIGITAL ELEVATION MODELS OF PUERTO RICO

3.4 Quality Assessment of the DEMs

3.4.1. Horizontal accuracy

The Puerto Rico DEMs have an estimated horizontal accuracy of 10 meters for topographic features. Bathymetric 

features are resolved only to within a few hundred meters in most deep-water areas; shallow, near-coastal regions 

have an accuracy approaching that of subaerial topographic features. Positional accuracy of deep-water bathymetric 

features is limited by large interpolation between scattered soundings, and by potentially large positional accuracy of 

pre-satellite navigated (GPS) hydrographic surveys.

3.4.2 Vertical accuracy

Vertical accuracy of elevation values for the Puerto Rico DEMs is dependent upon the source datasets contributing 

to DEM cell values. Topographic areas have an estimated vertical accuracy between 0.5 meters (for PROMB DEMs) 

and up to 7 meters (for NED topographic DEM). Bathymetric areas have an estimated accuracy of between 0.1 meters 

(coastal SHOALS and NOS LiDAR data) and ~2% of water depth (~100 meters in the deepest areas of the 1 arcsecond Puerto Rico DEM). Those values were derived from the wide range of input data sounding measurements from 

the early 20th century to recent, GPS-navigated multibeam sonar surveys. Gridding interpolation to determine values 

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

3.4.3 Slope maps and 3-D perspectives

ESRI ArcCatalog was used to generate slope grids from the Puerto Rico DEMs to allow for visual inspection 

and identification of artificial slopes along boundaries between datasets (e.g., Fig. 12). The DEMs were transformed

to UTM Zone 19 coordinates (horizontal units in meters) in ArcCatalog for derivation of the slope grid; equivalent 

horizontal and vertical units are required for effective slope analysis. Three-dimensional viewing of the UTMtransformed DEMs (e.g., Fig. 13) was accomplished using ESRI ArcScene. Analysis of preliminary DEMs revealed 

suspect data points, which were corrected before recompiling the DEMs. Figure 14 shows color images of the Puerto 

Rico DEMs in their final version.

Figure 12. Slope map of the 1/3 arc-second Fajardo DEM. Flat-lying slopes are white; dark shading 

denotes steep slopes; combined coastline in red.
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Taylor et al., 2008

Figure 13. Perspective view of the 1 arc-second Puerto Rico DEM. Vertical exaggeration times 3; 

combined coastline in black. 

Figure 14a. Color image of the 1 arc-second Puerto Rico DEM. Combined coastline in black.
21

DIGITAL ELEVATION MODELS OF PUERTO RICO

Figure 14b. Color image of the 1/3 arc-second San Juan DEM. Combined coastline in black.

Figure 14c. Color image of the 1/3 arc-second Fajardo DEM. Elevations colored as in Figure 14b; 

combined coastline in black.
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Taylor et al., 2008

Figure 14d. Color image of the 1/3 arc-second Guayama DEM. Elevations colored as in Figure 

14b; combined coastline in black.

Figure 14e. Color image of the 1/3 arc-second Ponce DEM. Elevations colored as in Figure 14b; 

combined coastline in black.
23

DIGITAL ELEVATION MODELS OF PUERTO RICO

Figure 14f. Color image of the 1/3 arc-second Mayagüez DEM. Elevations colored as in Figure 

14b; combined coastline in black.

Figure 14g. Color image of the 1/3 arc-second Arecibo DEM. Elevations colored as in Figure 14b; 

combined coastline in black.
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Taylor et al., 2008

3.4.4	 Comparison with source data files

To ensure grid accuracy, the Puerto Rico DEMs were compared to select source data files. Files were chosen on

the basis of their contribution to the grid-cell values in their coverage areas (i.e., had the greatest weight and did not 

significantly overlap other data files with comparable weight). A histogram of the differences between a SHOALS

bathymetric LiDAR survey file and the 1/3 arc-second Arecibo DEM is shown in Figure 15. Differences cluster around

zero, with only a handful of soundings—overlapping PROMB topographic elevations—exceeding 0.5 meter from the 

DEM. These are interpreted as anomalous soundings returned from the land surface rather than sea bottom.

Figure 15. Histogram of the differences between one SHOALS bathymetric LiDAR survey and the Arecibo DEM.

3.4.5 Comparison with NGS geodetic monuments

The elevations of 906 NOAA NGS geodetic monuments were extracted from online shape files of monument

datasheets (http://www.ngs.noaa.gov/cgi-bin/datasheet.prl), which give monument positions in NAD83 (sub-mm 

accuracy) and elevations in NAVD88 (in meters). Elevations were shifted to MHW vertical datum (see Table 10) 

for comparison with the Puerto Rico DEMs (see Fig. 16 for monument locations). Figure 17 shows the differences 

between the Ponce DEM and the NGS geodetic monuments, which range from -30 to 5 meters, with a negative value 

indicating that the DEM is less than the monument elevation. The monument with the largest offset from the DEM 

(TV0350, -30.13 meters) is located on the Muertos Island Lighthouse.
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DIGITAL ELEVATION MODELS OF PUERTO RICO

Figure 16. Location of NGS monuments and NOAA tide stations in the Puerto Rico region. NGS monument elevations were 

used to evaluate the Puerto Rico DEMs.

Figure 17. Histogram of the differences between NGS monuments and the Ponce DEM.
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Taylor et al., 2008

4. Summary and Conclusions

Combined topographic–bathymetric digital elevation models of Puerto Rico were built for the Pacific Marine

Environmental Laboratory (PMEL) NOAA Center for Tsunami Research. A 1 arc-second DEM was built that spans 

the entire island of Puerto Rico and offshore areas, as well as six 1/3 arc-second DEMs—centered on Arecibo, Fajardo, 

Guayama, Mayagüez, Ponce and San Juan—that completely encircle the island. The best available digital data from 

U.S. federal, state and local agencies, and academic institutions 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, FME, CARIS, GMT, MB-System, QT Modeler, and GEODAS software. 

Recommendations to improve the DEM based on NGDC’s research and analysis include:

•	 Correct artifacts in NED DEM introduced by USGS gridding algorithm and resolve vertical datum issues 

with this dataset.

•	 Conduct SHOALS bathymetric LiDAR surveys along southern coast of the Island of Puerto Rico, and around 

Mona and Desecheo islands.

•	 Include remaining NOS bathymetric LiDAR surveys around southwest portion of Puerto Rico once those 

surveys have been processed.

5. Acknowledgments

The creation of the Puerto Rico DEMs was funded by the NOAA Pacific Marine Environmental Laboratory. The

authors thank Chris Chamberlin, Angie Venturato, and Hal Mofjeld (PMEL), Aurelio Mercado Irizarry (University of 

Puerto Rico), Tim Blak (Dewberry and Davis, Inc.), Dave Doyle (NGS), Tony Kimmet and George Rohaley (USDA, 

National Resources Conservation Service), Ada Otter and Tim Battista (NOAA National Centers for Coastal Ocean 

Science), and Ivan Santiago (Puerto Rico Office of Management and Budget). Special thanks to Uri ten Brink and

Jason Chaytor (USGS, Woods Hole) for providing DEMs of their proprietary multibeam sonar surveys around Puerto 

Rico for use in this project.

6. References

Carbó, A., D. Córdoba, J. Martin Davila, U. ten Brink, P. Herranz, C. Von Hilldebrandt, J. Payero, A. Muñoz Martín, 

A. Pazos, M. Catalán, J.L. Granja, and M. Gómez, 2005. Survey explores active tectonics in northern Caribbean. 

Eos Trans. AGU, v. 86, no. 51, 537, 540.

Carbotte, S.M., R. Arko, D.N. Chayes, W. Haxby, K. Lehnert, S. O’Hara, W.B.F. Ryan, R.A. Weissel, T. Shipley, 

L. Gahagan, K. Johnson, and T. Shank, 2004. New Integrated Data Management System for Ridge2000 and 

MARGINS Research, Eos Trans. AGU v. 85, no. 51.

Martinez, R., G. Cintrón, and L. A. Encarnacion, 1979. Mangroves in Puerto Rico: A Structural Inventory, Department 

of Natural Resources, San Juan PR, USA, 149 pp.

Smith,W. H. F., and D.T. Sandwell, 1997. Globalseafloor topography from satellite altimetry and ship depth soundings,

Science, v. 277, p. 1957-1962.

ten Brink, U.S., and S. Smith, 2003. High-resolution bathymetric map for the Puerto Rico trench; implications for 

earthquake and tsunami hazards, Seismological Research Letters, v. 74, p. 230.

ten Brink, U.S., W. Danforth, C. Polloni, B. Andrews, P. Lanes, S. Smith, E. Parker, and T. Uozumi, 2004. New 

seafloor map of the Puerto Rico Trench helps assess earthquake and tsunami hazards. Eos Trans. AGU, v. 85, no. 

37, p. 349, 354.

National Centers for Coastal Ocean Science Biogeography Program, 2001. Benthic Habitats of Puerto Rico and the 

U.S. Virgin Islands, Silver Spring, MD, National Oceanic and Atmospheric Administration (CD-ROM). http://

biogeo.nos.noaa.gov/projects/mapping/caribbean/startup.htm
27

DIGITAL ELEVATION MODELS OF PUERTO RICO

7. Data Processing Software

ArcGIS v. 9.2, developed and licensed by ESRI, Redlands, California, http://www.esri.com/

CARIS Bathy DataBASE v. 2, developed and licensed by CARIS, Fredricton, NB, Canada, http://www.caris.com/

Electronic Navigational Chart Data Handler for ArcView, developed by NOAA Coastal Services Center, http://www.

csc.noaa.gov/products/enc/

FME 2006 GB – Feature Manipulation Engine, developed and licensed by Safe Software, Vancouver, BC, Canada, 

http://www.safe.com/

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

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

GMT v. 4.1.4 – Generic Mapping Tools, shareware developed and maintained by Paul Wessel and Walter Smith, 

funded by the National Science Foundation, http://gmt.soest.hawaii.edu/

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

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

Quick Terrain Modeler v. 6.0.1, LiDAR processing software developed by John Hopkins University’s Applied Physics 

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