noaa / NATIONAL OCEANIC AND

ATMOSPHERIC ADMINISTRATION

National Environmental Satellite,

Data, and Information Service

NOAA Technical Memorandum NESDIS NGDC-22

DIGITAL ELEVATION MODEL OF ASTORIA, OREGON:

PROCEDURES, DATA SOURCES AND ANALYSIS 

K.S. Carignan

L.A.Taylor

B.W. Eakins

R.R. Warnken

National Geophysical Data Center

Marine Geology and Geophysics Division

Boulder, Colorado

March 2009

UNITED STATES

DEPARTMENT OF COMMERCE

Gary Locke

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-22

DIGITAL ELEVATION MODEL OF ASTORIA, OREGON:

PROCEDURES, DATA SOURCES AND ANALYSIS 

Kelly S. Carignan1

Lisa A. Taylor2

Barry W. Eakins1

Robin R. Warnken2

1

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

2NOAA, National Geophysical Data Center, Boulder, Colorado 

National Geophysical Data Center

Marine Geology and Geophysics Division 

Boulder, Colorado

March 2009
Carignan et al., 2009

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/inundation/tsunami/inundation.html

Also available from the National Technical Information Service (NTIS)

(http://www.ntis.gov)
Digital Elevation Model of Astoria, Oregon

iii

Contents

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

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

3. Methodology ......................................................................................................................................3

3.1 Data Sources and Processing ......................................................................................................4

3.1.1 Shoreline................................................................................................................5

3.1.2 Bathymetry ............................................................................................................8

3.1.3 Topography..........................................................................................................20

3.2 Establishing Common Datums .................................................................................................28

3.2.1 Vertical datum transformations ...........................................................................28

3.2.2 Horizontal datum transformations.......................................................................28

3.3 Digital Elevation Model Development .....................................................................................29

3.3.1 Verifying consistency between datasets..............................................................29

3.3.2 Smoothing of bathymetric data ...........................................................................29

3.3.3 Gridding the data with MB-System......................................................................31

3.4 Quality Assessment of the DEM...............................................................................................32

3.4.1 Horizontal accuracy.............................................................................................32

3.4.2 Vertical accuracy .................................................................................................32

3.4.3 Slope maps and 3-D perspectives........................................................................33

3.4.4	 Comparison with source data files.......................................................................34

3.4.5 Comparison with NGS geodetic monuments......................................................35

4. Summary and Conclusions...............................................................................................................36

5. Acknowledgments............................................................................................................................36

6. References........................................................................................................................................36

7. Data Processing Software ................................................................................................................37

List of Figures

Figure 1. Shaded-relief image of the Astoria, Oregon DEM......................................................................1

Figure 2. Landsat 7 i-cubed satellite image of the Astoria DEM boundary...............................................2

Figure 3. Source and coverage of datasets used to compile the Astoria DEM...........................................4

Figure 4. Digital coastline datasets used in developing a coastline for the Astoria DEM .........................5

Figure 5. Levee at Toke Point.....................................................................................................................7

Figure 6. South Jetty at Clatsop Point........................................................................................................7

Figure 7. Spatial coverage of bathymetric datasets used to compile the Astoria DEM .............................9

Figure 8. Digital NOS hydrographic survey coverage in the Astoria region ...........................................12

Figure 9. Spatial coverage of NOS hydrographic survey H11723...........................................................13

Figure 10. Spatial USACE hydrographic survey coverage in the Astoria region ......................................15

Figure 11.	 Spatial coverage of multibeam swath sonar files from NGDC multibeam

database..............................................................................................................................16

Figure 12. QT Modeler image of anomalous data spikes in the NGDC multibeam sonar 

surveys...............................................................................................................................17

Figure 13. QT Modeler image of USGS multibeam survey mb99.............................................................18

Figure 14. NOS hydrographic survey smooth sheet from survey H04658 ................................................19

Figure 15. Spatial coverage of topographic datasets used in the Astoria DEM.........................................20

Figure 16. NED topographic data at Chehalis Point ..................................................................................21

Figure 17. NASA World Wind image of area north of Seaside, OR............................................................22

Figure 18. QT Modeler image of non-bare earth CSC ALACE LiDAR data before filtering

process. ..............................................................................................................................22

Figure 19. CSC Willapa Bay LiDAR.........................................................................................................23

Figure 20. QT Modeler image of PSLC Chehalis River LiDAR data points.............................................24

Figure 21. PSLC Columbia River LiDAR DEM tiles before processing steps .........................................25

Figure 22. Diagram of sections of the southern jetty on Clatsop Spit........................................................26
Carignan et al., 2009

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Figure 23. QT Modeler illustration of two cross sections at dataset transition between 

LiDAR datasets and NED..................................................................................................27

Figure 24. Preliminary bathymetric surface showing cross section of area containing 

ridges generated from surfacing raw USACE datasets......................................................29

Figure 25. USACE data in Grays Harbor before and after blockmean processing....................................30

Figure 26. Histogram of the differences between NOS hydrographic survey H08416 and 

the 1 arc-second pre-surfaced bathymetric grid.................................................................30

Figure 27. Slope map of the Astoria DEM.................................................................................................33

Figure 28. Perspective view of the Astoria DEM.......................................................................................34

Figure 29. Histogram of the differences between a section of the CSC ALACE LiDAR 

survey and the Astoria DEM..............................................................................................34

Figure 30. Histogram of the differences between NGS monuments and Astoria DEM.............................35

Figure 31. Location of NGS geodetic monuments and the NOAA tide station used in 

Astoria DEM......................................................................................................................35

List of Tables

Table 1.	 PMEL specifications for the Astoria, Oregon DEM ...................................................................3

Table 2. Shoreline datasets used in the Astoria DEM...............................................................................5

Table 3. Digital nautical charts available in the Astoria, Oregon region..................................................6

Table 4. Bathymetric datasets used in compiling the Astoria DEM.........................................................8

Table 5. Digital NOS hydrographic surveys used in compiling the Astoria DEM.................................10

Table 6. USACE surveys used in compiling the Astoria DEM ..............................................................14

Table 7. Multibeam surveys from NGDC database used in compiling the Astoria DEM......................16

Table 8. Topographic datasets used in compiling the Astoria DEM.......................................................20

Table 9. Relationship between Mean High Water and other vertical datums in the Astoria 

region .................................................................................................................................28

Table 10. Data hierarchy used to assign gridding weight in MB-System..................................................31
Digital Elevation Model of Astoria, Oregon:

Procedures, Data Sources and Analysis

1. Introduction

In May 2008, the National Geophysical Data Center (NGDC), an office of the National Oceanic and Atmospheric

Administration (NOAA), developed an integrated bathymetric–topographic digital elevation model (DEM) of Astoria, 

Oregon (Fig. 1) for the Pacific Marine Environmental Laboratory (PMEL) NOAACenter for Tsunami Research (http://

nctr.pmel.noaa.gov/). The 1/3 arc-second1 coastal DEM will be used as input for the Method of Splitting Tsunami 

(MOST) model developed by PMEL to simulate tsunami generation, propagation and inundation. The DEM was 

generated from diverse digital datasets in the region (grid boundary and sources shown in Fig. 3) and will be used 

for tsunami inundation modeling, as part of the tsunami forecast system SIFT (Short-term Inundation Forecasting for 

Tsunamis) developed by PMEL for the NOAA Tsunami Warning Centers. This report provides a summary of the data 

sources and methodology used in developing the Astoria DEM.

1. The Astoria DEM is 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 Astoria, Oregon (46°11.33′ N, 123°49.27′ W) 

1/3 arc-second of latitude is equivalent to 10.29 meters; 1/3 arc-second of longitude equals 7.15 meters.

Figure 1. Shaded-relief image of the Astoria, Oregon DEM. Contour 

interval is 50 meters in water and 100 meters on land. Image is in 

Mercator projection.
Carignan et al., 2009

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2. Study Area

The Astoria DEM covers the coastal area of the Willapa Hills physiographic province stretching from Seaside, 

Oregon north to Ocean Shores, Washington (Fig. 2). Formed from the Columbia River Basalt Group and coastal 

sediments, the region is characterized more by weathering than from deformation creating more rounded topography 

compared to the Olympic Mountains to the north. Encompassing the mouth of the Columbia River, the DEM region 

also includes two large estuaries, Willapa Bay and Grays Harbor. Willapa Bay is largely an intertidal zone with much 

of the water entering and retreating with the tide. Grays Harbor, to the north, also contains large areas of mud flats. 

Astoria was founded in 1810 as a fur trading port on the southern bank of the Columbia River. Tourism and 

light manufacturing have replaced the once booming fishing and lumber industries as the main economic sources.

Currently, Astoria has a population of approximately 10,000 over about a six square mile area. 

Figure 2. NASA World Wind i-cubed Landsat 7 image of Astoria DEM boundary shown in red (http://worldwind.arc.nasa.gov/).
Digital Elevation Model of Astoria, Oregon

3

3. Methodology

The Astoria, Oregon DEM was 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 to provide real-time tsunami forecasts in an 

operational environment. The best available digital data were obtained by NGDC and shifted to common horizontal 

and vertical datums: North America Datum 1983 (NAD 83) and Mean High Water (MHW), respectively, for modeling 

of maximum flooding2. Data processing and evaluation, and DEM assembly and assessment are described in the 

following subsections.

Table 1: PMEL specifications for the Astoria, Oregon DEM.

Grid Area Astoria, Oregon

Coverage Area 123.71o to 124.59o W; 45.94o to 47.09o N

Coordinate System Geographic decimal degrees

Horizontal Datum World Geodetic System 1984 (WGS 84)

Vertical Datum Mean High Water (MHW)

Vertical Units Meters

Grid Spacing 1/3 arc-second

Grid Format ESRI Arc ASCII 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 DEM. 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. This DEM is 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 DEM, WGS 84 and NAD 83 geographic are identical and may be used 

interchangeably.
Carignan et al., 2009

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3.1 Data Sources and Processing

Shoreline, bathymetric, and topographic digital datasets (Fig. 3) were obtained from several U.S. federal, state 

and local agencies including: NOAA’s National Ocean Service (NOS), Office of Coast Survey (OCS) and Coastal

Services Center (CSC); the U.S. Geological Survey (USGS); the U.S. Army Corps of Engineers (USACE); Washington 

State Department of Ecology; and the Puget Sound LiDAR Consortium (PSLC). Safe Software’s (http://www.safe.

com/) FME data translation tool package was used to shift datasets to NAD 83 horizontal datum and to convert them 

into ESRI (http://www.esri.com/) ArcGIS shape files3. The shape files were then displayed with ArcGIS to assess 

data quality and manually edit datasets. Vertical datum transformations to MHW were accomplished using FME and 

ArcGIS, based upon data from the NOAA tide stations. Applied Imagery’s Quick Terrain Modeler software (http://

www.appliedimagery.com/) was used for editing data and to evaluate processing and gridding techniques.

Figure 3. Source and coverage of datasets used to compile the Astoria DEM.

3. FME uses the North American Datum Conversion Utility (NADCON; http://www.ngs.noaa.gov/TOOLS/Nadcon/Nadcon.html) developed by 

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

83 datum transformations.
Digital Elevation Model of Astoria, Oregon

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3.1.1 Shoreline

Coastline datasets of the Astoria region were obtained from NOAA’s Office of Coast Survey as Electronic

Navigational Charts (ENCs) and Raster Nautical Charts (RNCs); the USGS; and the Washington State Department 

of Ecology (WASDOE). The coastlines varied in distance up to 500 meters from the most recent topographic LiDAR 

datasets, particularly at the inlets to the bays and at the mouth of the Columbia River. The ENC and RNC varied the 

least from the LiDAR datasets in most areas and were used to develop a complete coastline for the DEM region (Table 

2; Fig. 4).

Table 2: Shoreline dataset used in the Astoria DEM.

Source Year Data Type Spatial 

Resolution

Original Horizontal 

Datum/Coordinate 

System

Original Vertical 

Datum URL

OCS ENC 

extracted 

shoreline

2005 

to 

2007

vector 1:40,000 to 

1:185,238

WGS 84 geographic 

(meters) Mean High Water

http://chartmaker.

ncd.noaa.gov/

MCD/enc/index.

htm

OCS RNC 

derived 

coastline

2007 derived from 

raster data

1:20,000 to 

1:40,000

WGS 84 geographic 

(meters) Mean High Water

http://

nauticalcharts.

noaa.gov/mcd/

Raster/Index.htm

NGDC 

Garibaldi DEM 

coastline

2007 vector WGS 84 geographic Mean High Water

http://www.

ngdc.noaa.gov/

dem/showdem.

Figure 4. Digital coastline datasets used for developing a coastline for the Astoria DEM
Carignan et al., 2009

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1) OCS Raster Nautical Charts

 Five raster nautical charts (RNCs) were available for the Astoria area (Table 3) and downloaded from 

NOAA’s Office of Coast Survey website (http://nauticalcharts.noaa.gov/mcd/enc/index.htm). The RNCs are 

provided online as georeferenced raster images and cover the entire coastline within the DEM boundaries. 

A ‘derived coastline’ was generated using ArcGIS Spatial Analyst to extract the coastline from the raster 

image of the nautical chart based on pixel values. The resulting data were then resampled and converted to 

polylines. Further editing of the RNC coastline dataset was done to remove stray line segments in the open 

ocean using ArcMap editing tools.

2) OCS Electronic Navigational Charts

 Four electronic navigational charts (ENCs) were available for the Astoria area (Table 3) and downloaded 

from the NOAA’s Office of Coast Survey website (http://chartmaker.ncd.noaa.gov/MCD/enc/index.htm). The 

coastline data were extracted from the ENC S-57 format to vector line shapefiles. The ENC coastline dataset

covers the entire DEM area except the Chehalis River on the eastern DEM boundary. 

Table 3: Digital nautical chart data available in the Astoria, Oregon region.

Chart Title Edition Edition Date Format Scale

18500 Columbia River to Destruction Island 29 2004 ENC and RNC 1:180,789

18502 Greys Harbor - Westhaven Cove 86 2007 ENC and RNC 1:40,000

18504 Willapa Bay – Toke Point 66 2006 RNC 1:40,000

18520 Yaquina Head to Columbia River – Netarts Bay 26 2005 ENC and RNC 1:185,238

18521 Columbia River Pacific Ocean to Harrington

Point – Ilwaco Harbor 72 2005 ENC and RNC 1:40,000

3) NGDC Garibaldi DEM coastline

The southern Astoria DEM boundary overlaps the Garibaldi DEM (http://www.ngdc.noaa.gov/dem/

showdem.jsp?dem=Garibaldi&state=OR&cell=1/3%20arc-second) northern boundary by approximately 2 

kilometers. The coastline used in the Garibaldi DEM was clipped to the Astoria DEM boundary and merged 

with the OCS chart coastline datasets using ArcCatalog tools.
Digital Elevation Model of Astoria, Oregon

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Figure 5. Levee at Toke Point. Photo from Washington State Department of Ecology (http://apps.ecy.wa.gov/shorephotos/).

Figure 6. South Jetty at Clatsop Point. Photo from US Coast Guard (http://www.uscg.mil/d13/units/gruastoria/cd_aor_photo_gallery3.htm).

The merged coastline datasets were visually compared to Google Earth satellite imagery (http://earth.google.

com/userguide/v4/#imagery_dates), the Washington State Department of Ecology aerial photo collection (http://apps.

ecy.wa.gov/shorephotos/), and USGS topographic maps available on NASA World Wind (http://worldwind.arc.nasa.

gov/index.html) to ensure features such as jetties and levees were present in the coastline (Figs. 5 and 6). Finally, to 

represent the most recent topographic LiDAR data, the coastline was adjusted to match the LiDAR data available from 

the Puget Sound LiDAR Consortium (PSLC) where present and the Coastal Services Center 2002 ALACE LiDAR in 

the remaining areas along the coast.
Carignan et al., 2009

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3.1.2 Bathymetry

Bathymetric datasets used in the compilation of the Astoria DEM include 73 NOS hydrographic surveys, 34 

hydrographic channel line surveys from USACE, 11 multibeam swath sonar surveys downloaded from the NGDC 

multibeam sonar database, one multibeam sonar survey from the USGS, extracted ENC sounding data, and digitized 

RNC soundings (Table 4; Fig. 7).

Table 4: Bathymetric datasets used in compiling the Astoria DEM.

Source Year Data Type Spatial Resolution

Original 

Horizontal Datum/

Coordinate System

Original 

Vertical 

Datum

URL

NOS

1851 

to 

2005

Hydrographic 

survey 

soundings

Ranges from 10 

m to 1 km (varies 

with scale of survey, 

depth, traffic, and

probability of 

obstructions)

NAD 27 or NAD 

83 geographic

Mean Lower 

Low Water

http://www.ngdc.noaa.

gov/mgg/bathymetry/

hydro.html

NOS 2007 Multibeam 

Survey 1:20,000 NAD 83 UTM Zone 10 North

Mean Lower 

Low Water

USACE

2006 

to 

2007

Hydrographic 

channel line 

surveys

various, from 3 to 40 

meter point spacing

NAD 83 Oregon 

State Plane North 

(feet) or NAD 83 

Washington State 

Plane South

 Mean Lower 

Low Water

https://www.nwp.

usace.army.mil/op/

nwh/xyzcoastal.asp

NGDC 

1998 

to 

2003

Multibeam 

sonar swath 

files

raw MB files gridded

to 1 arc-second

WGS 84 

geographic

assumed 

Mean Sea 

Level

http://www.ngdc.noaa.

gov/mgg/bathymetry/

multibeam.html

USGS 1999 Multibeam ~ 10 meters

NAD 83 State 

Plane Washington 

South (meters)

MLLW

http://walrus.wr.usgs.

gov/swces/data.

html#era4

OCS RNC

2003 

to 

2005

digitized 

soundings from 

RNC

1:20,000 WGS 84 

geographic

Mean Lower 

Low Water

http://nauticalcharts.

noaa.gov/mcd/Raster/

Index.htm

OCS ENC 2005

extracted 

soundings from 

ENC

1: 191,730 WGS 84 

geographic

Mean Lower 

Low Water

http://chartmaker.ncd.

noaa.gov/MCD/enc/

index.htm
Digital Elevation Model of Astoria, Oregon

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Figure 7. Spatial coverage of bathymetric datasets used to compile the Astoria DEM.
Carignan et al., 2009

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1) NOS hydrographic survey data

A total of 73 NOS hydrographic surveys conducted between 1851 and 2005 were available for use in 

developing the Astoria DEM. The hydrographic survey data were originally vertically referenced to Mean 

Lower Low Water (MLLW) and horizontally referenced to either NAD 1913, NAD 27, or NAD 83 datums if 

the datum was known and recorded (Table 5; Fig. 8).

Data point spacing for the NOS surveys varied by collection date. In general, earlier surveys had greater 

point spacing than more recent surveys. All surveys were extracted from NGDC’s online NOS hydrographic 

database (http://www.ngdc.noaa.gov/mgg/bathymetry/hydro.html) referenced to NAD 83. The surveys were 

subsequently clipped to a polygon 0.05 degree (~5%) larger than the Astoria DEM area to support data 

interpolation along grid edges. 

After converting all NOS survey data to MHW, the data were displayed in ESRI ArcMap and reviewed 

for digitizing errors against scanned original survey smooth sheets and edited as necessary. The surveys 

were also compared to the topographic and other bathymetric datasets, the Astoria coastline, and NOS 

raster nautical charts (RNCs). The surveys were clipped to remove soundings that overlap the more recent 

multibeam surveys, USACE surveys, and where soundings from older surveys have been superseded by 

more recent NOS surveys.

 Table 5: Digital NOS hydrographic surveys used in compiling the Astoria DEM.

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

Digital Records

H00250 1851 20,000 Mean Lower Low Water unknown

H00335 1852 20,000 Mean Lower Low Water unknown

H00809 1862 20,000 Mean Lower Low Water NAD 27

H01019 1868 20,000 Mean Lower Low Water unknown

H01378 1877 40,000 Mean Lower Low Water NAD 1913

H01379 1877 40,000 Mean Lower Low Water NAD 1913

H01589A 1883/91 20,000 Mean Lower Low Water NAD 27

H01800 1887 40,000 Mean Lower Low Water NAD 27

H02103 1891 20,000 Mean Lower Low Water undetermined

H03297 1911 20,000 Mean Lower Low Water NAD 1913

H04363 1924 20,000 Mean Lower Low Water NAD 1913

H04611 1926 20,000 Mean Lower Low Water NAD 1913

H04612 1926 20,000 Mean Lower Low Water NAD 1913

H04618 1926 20,000 Mean Lower Low Water NAD 1913

H04619 1926 20,000 Mean Lower Low Water NAD 1913

H04620 1926 20,000 Mean Lower Low Water NAD 1913

H04621 1926 20,000 Mean Lower Low Water NAD 1913

H04633A 1926 120,000 Mean Lower Low Water NAD 1913

H04635 1926 40,000 Mean Lower Low Water NAD 27

H04636 1926 80,000 Mean Lower Low Water NAD 27

H04639 1926 120,000 Mean Lower Low Water NAD 27

H04634 1926/27 40,000 Mean Lower Low Water NAD 1913

H04710 1927 20,000 Mean Lower Low Water NAD 27

H04715 1927 20,000 Mean Lower Low Water NAD 1913

H04728 1927 40,000 Mean Lower Low Water NAD 27

H04729 1927 40,000 Mean Lower Low Water NAD 1913

H04735 1927 80,000 Mean Lower Low Water NAD 27

H04658 1927/28 15,000 Mean Lower Low Water NAD 27

H05927 1935 10,000 Mean Lower Low Water NAD 27
Digital Elevation Model of Astoria, Oregon

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H05928 1935 10,000 Mean Lower Low Water NAD 27

H05975 1935 10,000 Mean Lower Low Water NAD 27

H05976 1935 10,000 Mean Lower Low Water NAD 27

H06237 1935/37 2,500 Mean Lower Low Water NAD 27

H06178 1936 10,000 Mean Lower Low Water NAD 27

H06179 1936 10,000 Mean Lower Low Water NAD 27

H06180 1936/37 10,000 Mean Lower Low Water NAD 27

H06514 1939 10,000 Mean Lower Low Water NAD 27

H06515 1939 10,000 Mean Lower Low Water NAD 27

H06516 1939 10,000 Mean Lower Low Water NAD 27

H06517 1939 10,000 Mean Lower Low Water NAD 27

H06518 1939 10,000 Mean Lower Low Water NAD 27

H06519 1939 10,000 Mean Lower Low Water NAD 27

H06520 1939 10,000 Mean Lower Low Water NAD 27

H06521 1939 10,000 Mean Lower Low Water NAD 27

H06646 1940 10,000 Mean Lower Low Water NAD 27

H06647 1940 10,000 Mean Lower Low Water NAD 27

H06665 1941 10,000 Mean Lower Low Water NAD 27

H07178 1947 10,000 Mean Lower Low Water NAD 27

H07179 1947 5,000 Mean Lower Low Water NAD 27

H07180 1947 5,000 Mean Lower Low Water NAD 27

H07817 1950 10,000 Mean Lower Low Water NAD 27

H07940 1951 10,000 Mean Lower Low Water NAD 27

H08136 1954 10,000 Mean Lower Low Water NAD 27

H08137 1954 10,000 Mean Lower Low Water NAD 27

H08138 1954 15,000 Mean Lower Low Water NAD 27

H08335 1954 10,000 Mean Lower Low Water NAD 27

H08252 1955 20,000 Mean Lower Low Water NAD 27

H08250 1956 10,000 Mean Lower Low Water NAD 27

H08251 1956 10,000 Mean Lower Low Water NAD 27

H08292 1956 10,000 Mean Lower Low Water NAD 27

H08293 1956 10,000 Mean Lower Low Water NAD 27

H08423 1956/58 10,000 Mean Lower Low Water NAD 27

H08416 1958 20,000 Mean Lower Low Water NAD 27

H08417 1958 20,000 Mean Lower Low Water NAD 27

H08419 1958 10,000 Mean Lower Low Water NAD 27

H08420 1958 10,000 Mean Lower Low Water NAD 27

H08436 1958 5,000 Mean Lower Low Water NAD 27

B00115 1987 50,000 Mean Lower Low Water NAD 83

B00116 1987 50,000 Mean Lower Low Water NAD 83

F00430 1996/97 10,000 Mean Lower Low Water NAD 83

H11282 2005 10,000 Mean Lower Low Water NAD 83

H11299 2005 10,000 Mean Lower Low Water NAD 83

H11300 2005 10,000 Mean Lower Low Water NAD 83
Carignan et al., 2009

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Figure 8. Digital NOS hydrographic survey coverage in the Astoria region. Some older surveys were not used as they have been 

superseded by more recent surveys. DEM boundary in red.
Digital Elevation Model of Astoria, Oregon

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2) NOS hydrographic survey H11723 data

The most recent available NOS survey, H11723, was completed in 2007 and is located just outside 

the mouth of the Columbia River (Fig. 9). This multibeam survey was provided to NGDC in CARIS BAG 

gridded format by the NOS Pacific Hydrographic Branch directly after processing. The grid was converted

to xyz data using CARIS and transformed from NAD 83 UTM Zone 10 and MLLW to NAD 83 and MHW 

using FME.

Figure 9. Spatial coverage of NOS hydrographic survey H11723 from descriptive report available online (http://www.ngdc.noaa.gov/nndc/

servlet/ShowDatasets?dataset=101523&search_look=2&display_look=1,2). Adjacent survey H11724 is currently unavailable.
Carignan et al., 2009

14

3) USACE hydrographic channel line surveys

Thirty-four hydrographic channel line surveys (survey lines that run parallel to the channel, 7 lines 

across, spaced 150 feet apart) and cross line surveys (survey lines that run perpendicular, bank-to-bank 

and are spaced approximately 500 feet apart) were available for use in the Astoria DEM (Table 6, Fig. 

10). The surveys along the Columbia River were downloaded in xyz format from the USACE Portland 

District website (https://www.nwp.usace.army.mil/op/nwh/xyzcoastal.asp). Surveys located in Grays Harbor 

and Willapa Bay were obtained directly from the USACE Seattle District office. The data were transformed

to NAD 83 and MHW, changed to shape files using FME and quality checked in ArcMap against other 

bathymetric datasets.

Table 6: USACE hydrographic surveys used in compiling the Astoria DEM.

Survey ID Year Original 

Vertical Datum Original Horizontal Datum Survey Format

Columbia River - Deep water 

site 2007 MLLW NAD 83 State Plane Oregon North (feet)

Line spacing ~150 meters apart 

with ~50 meter point spacing

Columbia River - North Jetty 

site 2007 MLLW NAD 83 State Plane Oregon North (feet)

Line spacing ~30 meters apart with 

~60 meter point spacing

Columbia River - Shallow 

water site 2007 MLLW NAD 83 State Plane Oregon North (feet)

Line spacing ~60 meters apart with 

~60 meter point spacing

Columbia River - Site A 2005 MLLW NAD 83 State Plane Oregon North 

(feet)

Line spacing ~75 meters apart with 

~50 meter point spacing

Columbia River - Site B 2005 MLLW NAD 83 State Plane Oregon North 

(feet)

Line spacing ~75 meters apart with 

~60 meter point spacing

Columbia River - Site F 2005 MLLW NAD 83 State Plane Oregon North 

(feet)

Line spacing ~125 meters apart 

with ~50 meter point spacing

Columbia River - Flavel 

FLV022708 2008 MLLW NAD 83 State Plane Oregon North (feet) Channel line survey

Columbia River - Flavel 

FLVX010908 2008

MLLW NAD 83 State Plane Oregon North 

(feet) Cross line survey

Columbia River - Lower 

Desdemona LDS0022108 2008

MLLW NAD 83 State Plane Oregon North 

(feet) Channel line survey

Columbia River - Lower 

Desdemona ldsx 2008

MLLW NAD 83 State Plane Oregon North 

(feet) Cross line survey

Columbia River - Mouth of 

Columbia River MCR110807 2007

MLLW NAD 83 State Plane Oregon North 

(feet) Channel line survey

Columbia River - Miller Sands 

MLN022508 2008

MLLW NAD 83 State Plane Oregon North 

(feet) Channel line survey

Columbia River - Miller Sands 

mlnx 2008

MLLW NAD 83 State Plane Oregon North 

(feet) Cross line survey

Columbia River - Tongue Point 

TNG022208 2008

MLLW NAD 83 State Plane Oregon North 

(feet) Channel line survey

Columbia River - Tongue Point 

tngx

2008

MLLW NAD 83 State Plane Oregon North 

(feet) Cross line survey

Columbia River - Upper 

Desdemona UDS022108 2008

MLLW NAD 83 State Plane Oregon North 

(feet) Channel line survey

Columbia River - Upper 

Desdemona udsx 2008

MLLW NAD 83 State Plane Oregon North 

(feet) Cross line survey

Columbia River - Upper Sands 

USN022208 2008

MLLW NAD 83 State Plane Oregon North 

(feet) Channel line survey

Columbia River - Upper Sands 

USNX010808 2008

MLLW NAD 83 State Plane Oregon North 

(feet) Cross line survey

Grays Harbor - 0626 2007 MLLW NAD 83 State Plane Washington 

South (feet) Channel line survey

Grays Harbor - 0628 2007 MLLW NAD 83 State Plane Washington 

South (feet) Channel line survey

Grays Harbor - 0723 2007 MLLW NAD 83 State Plane Washington 

South (feet) Channel line survey

Grays Harbor - 0724 2007 MLLW NAD 83 State Plane Washington 

South (feet) Channel line survey

Grays Harbor - 0725 2007 MLLW NAD 83 State Plane Washington 

South (feet) Channel line survey
Digital Elevation Model of Astoria, Oregon

15

Grays Harbor - 0726 2007 MLLW NAD 83 State Plane Washington 

South (feet) Channel line survey

Grays Harbor - 0820 2007 MLLW NAD 83 State Plane Washington 

South (feet) Channel line survey

Willapa Bay - 2007wi003a 2007 MLLW NAD 83 State Plane Washington 

South (feet) Cross line survey

Willapa Bay - 2007wi003b 2007 MLLW NAD 83 State Plane Washington 

South (feet) Channel line survey

Willapa Bay - 10131 2007 MLLW NAD 83 State Plane Washington 

South (feet) Cross line survey

Willapa Bay - 20201 2007 MLLW NAD 83 State Plane Washington 

South (feet) Cross line survey

Willapa Bay - 210501 MLLW NAD 83 State Plane Washington 

South (feet) Channel line survey

Willapa Bay - allp 2007 MLLW NAD 83 State Plane Washington 

South (feet) Channel line survey

Willapa Bay - allx 2007 MLLW NAD 83 State Plane Washington 

South (feet) Cross line survey

Willapa Bay - r420830 2007 MLLW NAD 83 State Plane Washington 

South (feet) Cross line survey

Figure 10. Spatial coverage of USACE hydrographic channel line and cross line surveys for the Astoria DEM.
Carignan et al., 2009

16

4) Multibeam swath sonar files

Eleven multibeam swath sonar surveys were available from the NGDC multibeam database (http://www.

ngdc.noaa.gov/mgg/bathymetry/multibeam.html) for use in the Astoria DEM (Fig. 11, Table 7). This database 

is comprised of the original swath sonar files of surveys conducted mostly by the U.S. academic fleet. The

downloaded data were gridded to 1/3 arc-second resolution using MB-System. MB-System is an NSF-funded 

free software application specifically designed to manipulate submarine multibeam sonar data (http://www.

ldeo.columbia.edu/res/pi/MB-System/).

Most of the multibeam swath surveys offshore were transits rather than dedicated sea-floor surveys.

All have a horizontal datum of WGS 84 geographic and undefined vertical datum, and were assumed to be

referenced to mean sea level (MSL).

Table 7: Multibeam swath sonar files used in compiling the Astoria DEM.

Cruise ID Ship Year Original Vertical 

Datum

Original Horizontal 

Datum Institution

AT3L23 Atlantis 1998 assumed Mean Sea 

Level WGS 84 geographic Woods Hole Oceanographic Institution (WHOI)

AT03L24 Atlantis 1998 assumed Mean Sea 

Level WGS 84 geographic Woods Hole Oceanographic Institution (WHOI)

AT03L36 Atlantis 1999 assumed Mean Sea 

Level WGS 84 geographic Woods Hole Oceanographic Institution (WHOI)

AT03L37 Atlantis 1999 assumed Mean Sea 

Level WGS 84 geographic Woods Hole Oceanographic Institution (WHOI)

AT03L38 Atlantis 1999 assumed Mean Sea 

Level WGS 84 geographic Woods Hole Oceanographic Institution (WHOI)

AT3L53 Atlantis 1997 assumed Mean Sea 

Level WGS 84 geographic Woods Hole Oceanographic Institution (WHOI)

AT3L56 Atlantis 2000 assumed Mean Sea 

Level WGS 84 geographic Woods Hole Oceanographic Institution (WHOI)

AVON09MV Melville 1999 assumed Mean Sea 

Level WGS 84 geographic University of California, Scripps Institution of Oceanography (UC/SIO)

REM-01MV Melville 1993 assumed Mean Sea 

Level WGS 84 geographic University of California, Scripps Institution of Oceanography (UC/SIO)

REM-02MV Melville 1993 assumed Mean Sea 

Level WGS 84 geographic University of California, Scripps Institution of Oceanography (UC/SIO)

SO108 Sonne 1996 assumed Mean Sea 

Level WGS 84 geographic University of Kiel, Germany, GEOMAR Forshungszentrum

Figure 11. Spatial coverage of 

multibeam swath sonar files from 

NGDC multibeam database used 

in the Astoria region.
Digital Elevation Model of Astoria, Oregon

17

After assessing individual survey quality, the gridded data were transformed to MHW in xyz format 

using FME, displayed in QT Modeler and edited using ArcMap and QT Modeler. Figure 12 shows a band of 

anomalous data spikes in survey SO108, which were removed before use in the DEM. Another error in the 

multibeam data collection included swath edge rolling, “smiles and frowns”. These errors were manually 

edited at the edges where most pronounced, before creating a gridded bathymetric surface. 

Figure 12. QT Modeler image of anomalous data spikes in the NGDC multibeam sonar surveys. These spikes 

were removed by clipping out this section of trackline. 
Carignan et al., 2009

18

5) USGS Multibeam survey

The USGS multibeam survey, mb99, covered the offshore area between Willapa Bay and Grays Harbor 

and was downloaded from the USGS Southwest Washington Coastal Erosion Study website (http://walrus.

wr.usgs.gov/swces/data.html#era4). The survey was exported to a coverage from an .E00 file and changed to

a shapefile using ArcCatalog. Vertical and horizontal datums were transformed using FME. When displayed 

for analysis, the data revealed horizontal lines across the entire dataset and anomalous low data points not 

consistent with surrounding elevations or adjacent bathymetric data (Fig. 13). The lines and low data points 

were removed using ArcMap editing tools and QT Modeler.

Figure 13. QT Modeler image of USGS multibeam survey mb99. White arrows point to errors in data, which were removed before 

incorporation into bathymetric surface and final DEM.
Digital Elevation Model of Astoria, Oregon

19

6) Office of Coast Survey extracted ENC soundings

The OCS electronic navigational chart (ENC) sounding data were extracted from chart #18502 at Grays 

Harbor and #18521 at Ilwaco Harbor in Baker Bay where there was either no other bathymetric data available 

or existing data points were sparse. Soundings were transformed to MHW and clipped to the multibeam sonar 

surveys, the USACE hydrographic surveys, and the more recent NOS hydrographic surveys. Additional 

soundings were added to the ENC #18521 dataset at the head of the southern jetty at Clatsop Point to fill

in the submerged portion of the eroded jetty. Elevation values assigned to the points were determined by 

averaging the existing neighboring point elevations in NOS survey H08417. 

7) Office of Coast Survey digitized RNC soundings

At the entrance to Willapa Bay, soundings from RNC #18504 were digitized to ensure negative elevations 

in the bathymetric surface where no other digital sounding data were available.

Inconsistencies were identified while merging the bathymetric datasets due to the range in ages of the NOS

hydrographic surveys and differences in resolution. In areas where more recent data were available, the older NOS 

surveys were either edited or removed. Figure 14 illustrates the large amount of morphologic change that has occurred 

at Leadbetter Point since survey H04658 was completed. Soundings originally taken ~500 meter from the shoreline 

are now on land. This survey was not used in generating the bathymetric surface for the Astoria DEM.

Figure 14. NOS hydrographic survey smooth sheet from survey H04658 shown with Astoria coastline in red.
Carignan et al., 2009

20

3.1.3 Topography

Six topographic datasets in the Astoria region were obtained and used to build the Astoria DEM (Table 8; Fig. 

15). The USGS NED 1/3 arc-second provided full coverage for the DEM area and the 2002 CSC ALACE LiDAR 

dataset covered the entire coastline. The 2002 CSC Willapa Bay LiDAR provided higher resolution data for the 

inland area of Willapa Bay. Two datasets were downloaded from the Puget Sound LiDAR Consortium (PSLC) website 

covering the shoreline along the Columbia River and the Chehalis River. NGDC created an additional topographic 

dataset representing a coastal feature not fully resolved in the NED or CSC dataset. NGDC evaluated but did not use 

the Shuttle Radar Topography Mission (SRTM) Elevation 1 arc-second DEM available from USGS, as the higherresolution 1/3 arc-second NED DEMs provided complete coverage.

Table 8: Topographic datasets used in compiling the Astoria DEM.

Source Year Data Type Spatial

Resolution

Original Horizontal 

Datum/Coordinate 

System

Original 

Vertical 

Datum

URL

USGS 1999-

2006

NED 

DEM

1/3 arcsecond NAD 83 geographic NAVD88

(meters) http://ned.usgs.gov/

CSC 

ALACE 2002 LiDAR ~2 meters NAD 83 geographic NAVD88(meters) http://maps.csc.noaa.gov/TCM/

CSC 

Willapa 

Bay

2002 LiDAR ~2 meters NAD 83 geographic NAVD88

(meters) http://maps.csc.noaa.gov/TCM/

PSLC 

Columbia 

River

2005

LiDAR 

Bare 

earth 

DEMs

~1 meter 

grid

NAD 83 UTM 

Zone 10 North 

(meters)

NAVD88

(meters) http://pugetsoundlidar.ess.washington.edu/

PSLC 

Chehalis 

River

2002

LiDAR 

Bare 

earth

~1 meter

NAD 83 State Plane 

Washington North 

(feet)

NAVD88

(feet) http://pugetsoundlidar.ess.washington.edu/

NGDC

digitized 

elevation 

points

5 meters WGS 84 

(geographic) MHW

Figure 15. Spatial coverage of topographic datasets used 

in the Astoria DEM.
Digital Elevation Model of Astoria, Oregon

21

1) USGS NED topographic 1/3 arc-second DEMs

The U.S. Geological Survey (USGS) National Elevation Dataset (NED; http://ned.usgs.gov/) provides 

complete 1/3 arc-second coverage of the Astoria region4. Data are in NAD 83 geographic coordinates and 

NAVD88 vertical datum (meters), and are available for download as raster DEMs. The bare-earth elevations 

have a vertical accuracy of +/- 7 to 15 meters depending on source data resolution. See the USGS Seamless 

web site for specific source information (http://seamless.usgs.gov/). The dataset was derived from USGS 

quadrangle maps and aerial photographs based on topographic surveys; it has been revised using data 

collected in 1999 and 2000. The NED DEM included “zero” elevation values over the open ocean, which 

were removed from the dataset by clipping to the combined coastline. The clipping process also removed 

artifacts shown in Figure 16. 

Figure 16. NED topographic data at Chehalis Point. Red arrows point to artifacts present in the raw dataset.

4. 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 NAD 83, except for AK, which is NAD 27. 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]
Carignan et al., 2009

22

2) CSC LiDAR ALACE topography

The 2002 NASA/USGS Airborne LiDAR Assessment of Coastal Erosion (ALACE) Project topographic 

LiDAR dataset was downloaded from the NOAA CSC website (http://maps.csc.noaa.gov/TCM/) and 

transformed to NAD 83 and MHW using FME. As this dataset was not processed to bare earth and contained 

elevation values over open water as well as vegetation and buildings, NGDC processed the data using FME to 

simulate bare earth. The data were compared to the USGS NED topographic DEM and points were retained 

where the difference in elevation between the NED and the LiDAR data points was less than 12 meters. Most 

tall buildings and vegetation were eliminated while the high sand dunes and berms along the beaches remain 

(Figs. 17 and 18). This technique also created a smoother seam between the topographic datasets. The data 

were then clipped to the Astoria coastline and filtered to remove elevation points below zero.

Figure 17. NASA World Wind image of area 

north of Seaside, OR. Elevation of sand dunes 

reach 67 feet.

Figure 18. QT Modeler image 

of non-bare earth CSC ALACE 

LiDAR data before filtering 

process. 
Digital Elevation Model of Astoria, Oregon

23

3) CSC LiDAR Willapa Bay topography

The 2002 Willapa Bay LiDAR Project data were downloaded from the CSC website as points in NAD 

83 and NAVD88 datums. This project was flown at low tide to capture topographic surface elevation of the

exposed intertidal flats and surrounding land areas. The dataset is not designated as bathymetric–topographic

because the returns are from land surface at low tide as opposed to returns below water line. The data were 

transformed to NAD 83 and MHW using FME before editing. Visualizing the point data in QT Modeler

revealed some processing artifacts in the form of horizontal lines along the flight lines throughout the dataset

(Fig. 19). This required manual editing in QT Modeler before converting to xyz format for final gridding.

Data points close to shore and on shoal areas in the bay were retained for use in creating a bathymetric 

surface.

Figure 19. CSC Willapa Bay LiDAR. Red arrows point to linear artifacts that were clipped from data before 

final gridding.
Carignan et al., 2009

24

4) PSLC LiDAR Chehalis River bare earth topography

The PSLC Chehalis River LiDAR data were downloaded from the PSLC website (http://pugetsoundlidar.

ess.washington.edu/) in ~1 meter resolution point file format and processed to bare earth. The data were

converted from NAD 83 State Plane Washington North (feet) and NAVD88 to NAD 83 and MHW using 

FME. Data points over water, shown below in Fig. 20 as darker blue, were removed by clipping to the Astoria 

coastline using ArcCatalog tools.

Figure 20. QT Modeler image of PSLC Chehalis River LiDAR data points. Darker blue points in rivers were removed from dataset before 

final gridding process.
Digital Elevation Model of Astoria, Oregon

25

5) PSLC LiDAR Columbia River bare earth DEMs

The PSLC Columbia River bare earth DEMs were downloaded from the PSLC website (http://

pugetsoundlidar.ess.washington.edu/) as ESRI interchange files and converted to raster format using

ArcCatalog tools. FME was then used to transform to NAD 83 and MHW, convert to xyz format, and filter out

elevation points below -1 meter. Data tiles along the coastline were converted to point shapefiles and clipped

to the coastline before final gridding. The green band in the upper right corner of Figure 21 illustrates a

section of positive elevation points over the Columbia River that were removed by clipping to the coastline.

Figure 21. PSLC Columbia River LiDAR DEM tiles before processing steps. Data are in UTM coordinates and referenced to NAVD88.
Carignan et al., 2009

26

6) NGDC digitized jetty

The southern jetty on Clatsop Spit was not resolved in any of the topographic datasets. In order to ensure 

the feature was represented in the final DEM, a row of points was created along the jetty with an elevation of

3 meters. The USACE web site for jetties located at the mouth of the Columbia River provided the elevation 

information used (https://www.nwp.usace.army.mil/issues/jetty/documents.asp). The web site also provides 

updates on jetty reconstruction for this area. The diagram in Figure 22 shows a comparison of the cross 

sections of the south jetty from 2005, in blue, and the proposed structure, in green.

Figure 22. Diagram of sections of the southern jetty on Clatsop Spit from Final Environmental Assessment Repair of North and South Jetties 

Mouth of Columbia River (https://www.nwp.usace.army.mil/issues/jetty/docs/finalea25jan05.pdf). Blue line illustrates the cross section of the jetty 

in 2005. Green line is proposed jetty reconstruction cross section. 
Digital Elevation Model of Astoria, Oregon

27

After processing, the topographic data were viewed in ArcMap to make sure that the transitions along dataset 

edges were smooth. In some areas, the transition between the NED data and the LiDAR data formed a step ranging 

from 1 to 5 meters. A 75 meter data buffer was generated in the NED data to reduce the sharpness of this transition. 

Figure 23 shows the non-buffered and buffered cross sections in one area. Data were then converted to xyz format 

using FME for the final gridding process.

Figure 23. QT Modeler illustration of two cross sections at dataset transition between LiDAR at the top of image and NED below. The red line in 

profile represents a preliminary DEM surface before using buffer in transition zone. Teal line is final DEM surface using buffer. 
Carignan et al., 2009

28

3.2 Establishing Common Datums

3.2.1 Vertical datum transformations

Datasets used in the compilation and evaluation of the Astoria DEM were originally referenced to a number of 

vertical datums including Mean Lower Low Water (MLLW), Mean Sea Level (MSL), and NAVD88. All datasets were 

transformed to MHW to provide the maximum flooding for inundation modeling. Units were converted from feet to

meters as appropriate.

1) Bathymetric data

NGDC created two offset grids approximating the relationship between MLLW and MHW, and MSL 

and MHW for the west coast of Oregon and Washington. The grids were built in ArcGIS using the Inverse 

Distance Weighting (IDW) tool and the differences between the vertical datums as measured at 25 NOAA 

tide stations in the area (http://tidesandcurrents.noaa.gov/). The grids spanned from 40.7167° to 48.4167° N, 

and 124.6867° to 122.8868° W with a grid cell size of 0.1 degrees. The NOS hydrographic surveys, USGS 

and NGDC multibeam surveys, USACE surveys, and the nautical chart soundings were transformed from 

MLLW and MSL to MHW, using FME software, by adding the appropriate offset grid.

2) Topographic data

NGDC created an offset grid approximating the relationship between NAVD88 and MHW along the 

Pacific Northwest coast. The grid was built in ArcGIS using the Inverse Distance Weighting (IDW) tool 

and the difference between the vertical datums as measured at 16 NOAA tide stations in the region (http://

tidesandcurrents.noaa.gov/). The grids spanned from 40.7167° to 48.4167° N, and 124.6867° to 122.8868° W 

with a grid cell size of 0.1 degrees. The USGS NED 1/3 arc-second DEMs, the PSLC topographic LiDAR, 

and the CSC topographic LiDAR data were originally referenced to NAVD88. Conversion to MHW, using 

FME software, was accomplished by adding the offset grid to the survey data.

Table 9. Relationship between Mean High Water and other vertical datums at the Astoria tide station #9431647.

Vertical datum Difference to MHW in meters

MSL -2.466

NAVD88 -1.043

MLLW -2.428

3.2.2 Horizontal datum transformations

Datasets used to compile the Astoria DEM were originally referenced to WGS 84 geographic, NAD 83 geographic, 

NAD 27 geographic, NAD 1913, NAD 83 Oregon State Plane North, NAD 83 State Plane Washington South, NAD 

83 State Plane Washington North, and NAD 83 UTM Zone 10 North datums. The relationships and transformational 

equations between these horizontal datums are well established. All data were converted to a horizontal datum of NAD 

83 geographic using FME software or ArcGIS.
Digital Elevation Model of Astoria, Oregon

29

3.3 Digital Elevation Model Development

3.3.1 Verifying consistency between datasets

After horizontal and vertical transformations were applied, the resulting ESRIshape files were checked in ArcMap

for consistency between datasets. 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:

•	 Suspect topographic elevations located on open-ocean in both NED and LiDAR datasets.

•	 Inconsistencies between the NED and LiDAR topographic data. 

•	 Data errors in multibeam swath sonar surveys, which were expressed as anomalous spikes. Manual editing of 

the multibeam sonar data were necessary to minimize these artifacts. 

•	 Topographic CSC LiDAR dataset not processed to bare earth. The dataset required filtering of elevation

values on land and removal of returns from the water surface.

•	 Digital, measured bathymetric values from NOS surveys date back over 100 years. More recent data, such as 

the USACE hydrographic survey depths, differed from older NOS data by as much as 10 meters nearshore 

and up to 75 meters in deeper water compared to multibeam data. The older NOS survey data were excised 

where more recent bathymetric data exists.

3.3.2 Smoothing of bathymetric data

The NOS hydrographic surveys are generally sparse at the resolution of the 1/3 arc-second Astoria DEM: in both 

deep water and in some areas close to shore, the NOS survey data have point spacing up to 1900 m apart. In order to 

reduce the effect of artifacts in the form of lines of “pimples” in the DEM due to these low-resolution datasets, and 

to provide effective interpolation into the coastal zone, a 1 arc-second-spacing ‘pre-surface’ bathymetric grid was 

generated using GMT, an NSF-funded share-ware software application designed to manipulate data for mapping 

purposes (http://gmt.soest.hawaii.edu/).

To further reduce the interpolation errors between high resolution multibeam and the channel line USACE 

surveys, the USACE surveys in the Grays Harbor area were blockmeaned using GMT in order to “densify” the data 

and reduce the rippled effect (Figs. 24 and 25). This technique was also used on USACE survey 210501 at the entrance 

to the Columbia River.

Figure 24. A preliminary bathymetric 

surface showing cross section of area 

containing ridges generated from 

surfacing raw USACE datasets.
Carignan et al., 2009

30

Figure 25. USACE data in Grays Harbor before and after blockmean processing. A) Raw data points of channel line surveys colored by 

elevation. B) Blockmean data points of same surveys.

The NOS hydrographic point data, in xyz format, were clipped to remove overlap with the USACE soundings, 

NGDC multibeam data, USGS multibeam survey data, and nautical chart sounding data and combined into a single 

file, along with points extracted from the combined coastline—to provide a buffer along the entire coastline. The

coastline elevation value was set at -1.0 m to ensure a bathymetric surface below zero in areas where data are sparse 

or non-existent. The CSC Willapa Bay LiDAR data were included in creating the bathymetric surface, as the project 

was flown at low tide specifically to record elevation of tidal flats located within the bay.

The point data were median-averaged using the GMT tool ‘blockmedian’ to create a 1 arc-second grid 0.05 degrees 

(~5%) larger than the Astoria DEM gridding region. The GMT tool ‘surface’ was then 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 combined coastline (to eliminate data interpolation into land areas).

The resulting surface was compared with original soundings to ensure grid accuracy (e.g., Fig. 26) and exported as an 

xyz file for use in the final gridding process (see Table 10).

Figure 26. Histogram of the differences between NOS hydrographic survey H08416 and the 1 arc-second pre-surfaced 

bathymetric grid.
Digital Elevation Model of Astoria, Oregon

31

3.3.3 Gridding the data with MB-System

MB-System (http://www.ldeo.columbia.edu/res/pi/MB-System/) was used to create the 1/3 arc-second Astoria 

DEM. MB-System is an NSF-funded free software application specifically designed tomanipulate submarinemultibeam

sonar data, though it can utilize a wide variety of data types, including generic xyz data. 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 10. Greatest weight was given 

to the CSC LiDARand USACE survey data. Least weight was given to the pre-surfaced 1 arc-second bathymetric grid 

and Astoria coastline. Gridding was performed in quadrants, with the resulting Arc ASCII grids seamlessly merged in 

ArcCatalog to create the final 1/3 arc-second Astoria DEM.

 Table 10. Data hierarchy used to assign gridding weight in MB-System.

Dataset Relative Gridding Weight

CSC topographic LiDAR 1,000

USGS Multibeam survey 10

NGDC Multibeam surveys 10

USACE surveys 1,000

Nautical chart soundings 10

USGS NED topographic DEM 100

PSLC LiDAR 10,000

NOS hydrographic surveys 10

NOS survey H11723 1,000

Astoria coastline 1

NGDC digitized jetty 10,000

Pre-surfaced bathymetric grid 1
Carignan et al., 2009

32

3.4 Quality Assessment of the DEM

3.4.1. Horizontal accuracy

The horizontal accuracy of topographic and bathymetric features in the Astoria DEM is dependent upon the 

datasets used to determine corresponding DEM cell values. Topographic features have an estimated accuracy of 10 

meters: PSLC topographic LiDAR data have an accuracy of less then 1 meter, CSC topographic LiDAR data have 

an accuracy between 1 and 3 meters; NED topography is accurate to within about 10 meters. Bathymetric features 

are resolved only 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; potentially large positional uncertainty of pre-satellite navigated (e.g., GPS) NOS 

hydrographic surveys; and by manmade morphologic change (e.g., channel dredging and building of jetties).

3.4.2 Vertical accuracy

Vertical accuracy of elevation values for the Astoria DEM is also highly dependent upon the source datasets 

contributing to DEM cell values. Topographic areas have an estimated vertical accuracy between 0.1 to 0.3 meters for 

CSC LiDAR and PSLC LiDAR data, and up to 7 meters for NED topography. Bathymetric areas have an estimated 

accuracy of between 0.1 meters and 5% of water depth. Those values were derived from the wide range of input 

sounding data measurements from the early 20th century to recent, GPS-navigated sonar surveys. Gridding interpolation 

to determine values between sparse, poorly-located NOS soundings degrades the vertical accuracy of elevations in 

deep water.
Digital Elevation Model of Astoria, Oregon

33

3.4.3 Slope maps and 3-D perspectives

ESRI ArcCatalog was used to generate a slope grid from the Astoria DEM to allow for visual inspection and 

identification of artificial slopes along boundaries between datasets (e.g., Fig. 27). The DEM was transformed to UTM

Zone 10 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 revealed suspect data points, 

which were corrected before recompiling the DEM. Three-dimensional viewing of the UTM-transformed DEM was 

accomplished using ESRI ArcScene. Figure 28 shows a color image of the 1/3 arc-second Astoria DEM in its final

version.

Figure 27. Slope map of the Astoria DEM. Flat-lying slopes are white; dark shading denotes steep 

slopes; Astoria coastline in red.
Carignan et al., 2009

34

Figure 28. Perspective view from the southwest of the Astoria DEM. 4x vertical 

exaggeration.

3.4.4	 Comparison with source data files

To ensure grid accuracy, the Astoria DEM was 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 section of the

non-bare earth CSC ALACE LiDAR survey file located on Cape Disappointment and the Astoria DEM is shown in

Figure 29. Differences range from -36.54 to 29.3 meters. Negative values result from the elevation of the LiDAR data 

being higher than the DEM elevation. The area where the greatest difference occurred is on the heavily vegetated steep 

hillsides just north of Cape Disappointment at North Head.

Figure 29. Histogram of the differences between a section of the CSC ALACE LiDAR survey and the Astoria DEM.
Digital Elevation Model of Astoria, Oregon

35

3.4.5 Comparison with NGS geodetic monuments

The elevations of 710 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 NAD 83 (typically 

sub-mm accuracy) and elevations in NAVD88 (in meters). Monuments installed on lighthouses or buildings were not 

included in assessment of the DEM.

 Elevations were shifted to MHW vertical datum (see Table 10) for comparison with the Astoria DEM (see Fig. 

31 for monument locations). Differences between the Astoria DEM and the NGS geodetic monument elevations range 

from -86.62 to 180.12 meters, with the majority of them within ± 10 meters (Fig. 30). Negative values indicate that the 

DEM is less than the monument elevation. Monuments located in a lighthouse, on steep embankments, on a removed 

church tower, and lost monuments had the greatest negative values. The monuments with the greatest positive values 

were located at the top of a steep hill, at the top of a lighthouse, and on top of Astoria Column. The elevation recorded 

for the lighthouse monument was listed as the height of the lighthouse, not the height of the lighthouse plus the 

elevation of the cliff where it is located. Astoria Column is 125 ft (38.1 meters) high on top of a hill above the town, 

yet the monument elevation is recorded as 2 meters. The horizontal accuracy of some of these monuments could be 

off by ± 6 arc-seconds (~180 meters).

Figure 30. Histogram of the differences between NGS geodetic monument elevations and the Astoria DEM.

Figure 31. Location of NGS geodetic monuments, 

shown as green triangles, and the NOAA tide 

stations, red circles. NGS monument elevations 

were used to evaluate the DEM.
Carignan et al., 2009

36

4. Summary and Conclusions

An integrated bathymetric–topographic digital elevation model of the Astoria, Oregon region, with cell spacing of 

1/3 arc-second, was developed for the Pacific Marine Environmental Laboratory (PMEL) NOAA Center for Tsunami

Research. The best available digital data from U.S. federal, state and local 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, FME, GMT, MB-System, CARIS, and Quick Terrain Modeler

software. 

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

•	 Conduct hydrographic surveys in near-shore areas, especially in bays and river inlets.

•	 Complete bathymetric–topographic LiDAR surveying of entire region.

•	 Process CSC topographic LiDAR data to bare earth.

•	 Conduct hydrographic surveys to replace older, low-resolution NOS surveys in some deep water areas.

•	 Include deep water multibeam survey of Astoria Canyon and NOS hydrographic survey H11724, neither of 

which were available for use in this DEM.

5. Acknowledgments

The creation of theAstoria DEM wasfunded by the NOAAPacific Marine Environmental Laboratory. The authors

thank Chris Chamberlin and Vasily Titov (PMEL); Daniel Proudfit (U.S. Army Corps of Engineers, Portland District);

Lonnie Reid-Pell and Franchesca Gilbert (U.S. Army Corps of Engineers, Seattle District); Ann Gibbs (USGS Pacific

Science Center); Jeff Lillycrop (JALBTCX); and Brooke McMahon (NOAA/NOS Pacific Hydro Office).

6. References

Nautical Chart #18500 (RNC and ENC), 29nd Edition, 2004. Columbia River to Destruction Island. Scale 1: 180,789. 

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

Nautical Chart #18502 (ENC and RNC), 86th Edition, 2007. Greys Harbor – Westhaven Cove. Scale 1:40,000. U.S. 

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

Nautical Chart #18504 (RNC), 66th Edition, 2006. Willapa Bay – Toke Point. Scale 1:40,000. U.S. Department of 

Commerce, NOAA, National Ocean Service, Coast Survey.

Nautical Chart #18520 (ENC and RNC), 26th Edition, 2005. Yaquina Head to Columbia River – Netarts Bay. Scale 

1:185,238. U.S. Department of Commerce, NOAA, National Ocean Service, Coast Survey.

Nautical Chart #18521 (ENC and RNC), 72nd Edition, 2005. Columbia River Pacific Ocean to Harrington Point

– Ilwaco Harbor. Scale 1:196,948. U.S. Department of Commerce, NOAA, National Ocean Service, Coast 

Survey.

U.S. Army Corps of Engineers, Portland District. 2005. Final Environmental Assessment Repair of North and South 

Jetties Mouth of the Columbia River Clatsop County, Oregon and Pacific County, Washington. https://www.nwp.

usace.army.mil/issues/jetty/documents.asp
Digital Elevation Model of Astoria, Oregon

37

7. Data Processing Software

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

FME 2008 GB – Feature Manipulation Engine, developed and licensed by Safe Software, Vancouver, BC, Canada, 

http://www.safe.com/

GEODAS v. 5 – Geophysical Data System, free software 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, free software 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, free software 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/

CARIS Bathy DataBASE 2.0, bathymetric data processing software developed and licensed by CARIS, Fredericton, 

NB, Canada, http://www.caris.com/