i

NOAA Technical Memorandum NOS CS 16

VDATUM FOR THE LONG ISLAND SOUND, 

NARRAGANSETT BAY, AND NEW YORK BIGHT: TIDAL 

DATUMS, MARINE GRIDS, AND SEA SURFACE 

TOPOGRAPHY 

Silver Spring, Maryland 

November 2008 

noaa National Oceanic and Atmospheric Administration 

U.S. DEPARTMENT OF COMMERCE 

National Ocean Service 

Coast Survey Development Laboratory 
ii

Office of Coast Survey 

National Ocean Service 

National Oceanic and Atmospheric Administration 

U.S. Department of Commerce

The Office of Coast Survey (OCS) is the Nation’s only official chartmaker. As the 

oldest United States scientific organization, dating from 1807, this office has a 

long history. Today it promotes safe navigation by managing the National 

Oceanic and Atmospheric Administration’s (NOAA) nautical chart and 

oceanographic data collection and information programs. 

There are four components of OCS: 

The Coast Survey Development Laboratory develops new and efficient 

techniques to accomplish Coast Survey missions and to produce new and 

improved products and services for the maritime community and other 

coastal users. 

The Marine Chart Division acquires marine navigational data to construct 

and maintain nautical charts, Coast Pilots, and related marine products for 

the United States. 

The Hydrographic Surveys Division directs programs for ship and shorebased hydrographic survey units and conducts general hydrographic 

survey operations. 

The Navigational Services Division is the focal point for Coast Survey 

customer service activities, concentrating predominately on charting 

issues, fast-response hydrographic surveys, and Coast Pilot updates. 
iii

NOAA Technical Memorandum NOS CS 16 

VDATUM FOR THE LONG ISLAND SOUND, 

NARRAGANSETT BAY, AND NEW YORK BIGHT: TIDAL 

DATUMS, MARINE GRIDS, AND SEA SURFACE 

TOPOGRAPHY 

Zhizhang Yang, Emily. A. Dhingra, Kurt W. Hess, Adeline M. Wong and 

Edward P. Myers 

Office of Coast Survey, Coast Survey Development Lab, Silver Spring, 

MD 

Stephen A. White 

National Geodetic Survey, Silver Spring, MD 

November 2008

noaa National Oceanic and Atmospheric Administration 

U. S. DEPARTMENT National Oceanic and National Ocean Service 

OF COMMERCE Atmospheric Administration John H. Dunnigan 

Carlos Gutierrez, Secretary Conrad C. Lautenbacher, Jr., Assistant Administrator 

 VADM USN (Ret.), Under Secretary 

 Office of Coast Survey Coast Survey Development Laboratory 

 Captain Steven R. Barnum, NOAA Mary Erickson 
iv

NOTICE 

Mention of a commercial company or product does not constitute an 

endorsement by NOAA. Use for publicity or advertising purposes of 

information from this publication concerning proprietary products or 

the tests of such products is not authorized.
v

TABLE OF CONTENTS

LIST OF FIGURES .........................................................................................................................v 

LIST OF TABLES ......................................................................................................................... vi 

ABSTRACT .................................................................................................................................. vii 

1. INTRODUCTION .......................................................................................................................1 

2. COASTLINE, BATHYMETRY, AND TIDAL DATUM OBSERVATIONS ...........................3 

2.1. Digital Coastline ...........................................................................................................3 

 2.2. Bathymetric Data ..........................................................................................................3 

2.3. Tidal Datum Observations ............................................................................................5 

3. TIDAL DATUM SIMILATION ..................................................................................................7 

3.1. Tidal and Hydrodynamic Model ...................................................................................7 

 3.2. Model Grid ....................................................................................................................8 

3.3. Bathymetry ..................................................................................................................10 

3.4. Boundary Forcing and Model Run .............................................................................11 

3.5. Results .........................................................................................................................13 

3.6. Verifications and Error Corrections ............................................................................15 

4. CREATION AND POPULATION OF THE MARINE GRID .................................................21 

4.1. Creation of VDatum Marine Grid ...............................................................................23 

4.2. Population of VDatum Grid with Tidal Datums .........................................................25 

4.3. Comparison with Previous Results .............................................................................27 

5. TOPOGRAPHY OF THE SEA SURFACE ..............................................................................33 

6. SUMMARY ...............................................................................................................................37 

ACKNOWLEDGMENTS .............................................................................................................37

REFERENCES ..............................................................................................................................37 

APPENDIX A. SPECIFICATIONS OF BATHYMETRIC DATA ..............................................41 

APPENDIX B. WATER LEVEL STATION DATA ....................................................................43 

APPENDIX C. TCARI-CORRECTED TIDAL DATUM FIELDS ON THE 

UNSTRUCTURED MODEL GRID ..................................................................................51 

APPENDIX D. TIDAL GAUGE AND BENCHMARKS DATA USED TO CREATE 

THE TSS ............................................................................................................................53 

APPENDIX E. COMPARISON OF DERIVED TTS WITH OBSERVATIONS AND 

ERROR ANALYSIS. ........................................................................................................57 

 
vi
vii

LIST OF FIGURES 

Figure 1. Map of the Long Island Sound, New York Harbor, and Narragansett Bay area. 

Red lines illustrate MHW coastline and the green line denotes a distance 25-nautical 

miles offshore ...................................................................................................................................2 

Figure 2. Dates and locations of NOS sounding surveys .................................................................4 

Figure 3. Spatial distribution of the ENC bathymetric data .............................................................5 

Figure 4. Spatially variable bottom friction coefficient (Cd) employed in model 

computation......................................................................................................................................8 

Figure 5. Finite element grid for the entire model domain. Blue line represents the model 

open boundary. Numbers labelled along the boundary denote the node identification 

numbers of adjacent red dots. ..........................................................................................................9 

Figure 6. Zoom of the model grid near the (a) New York Harbor, (b) Narragansett Bay, 

and (c) Long Island Sound. ............................................................................................................10 

Figure 7. Model grid bathymetry relative to MSL. Color bar is in meters ....................................12 

Figure 8. M2 amplitudes on the model open boundary nodes. Blue circles represent those 

interpolated from WNATM and red triangles denotes those after adjustment. Locations of 

the open boundary nodes are illustrated in Figure 5. .....................................................................13 

Figure 9. Model derived MSL field relative to MS (units are cm) ................................................14 

Figure 10. Tidal datum fields, (a) MHHW, (b) MHW, (c) MLW, and (d) MLLW relative 

to MSL, as computed by the hydrodynamic model. Color bars are in meters.. .............................16 

Figure 11. Comparisons of the modeled (1) MHHW, (2) MHW, (3) MLW, and (4) 

MLLW datums against observations. ............................................................................................17 

Figure 12.1. Color-coded model-data errors at control stations over (a) the whole domain 

and (b) LIS. The errors represent averaged magnitudes of the model-data difference over 

four tidal datums, MHHW, MHW, MLW, and MLLW. The red numbers correspond to 

station numbers listed on the first column of Tables B.1 and B.2. Color bars are in cm ..............18 

Figure 12.2. Color-coded model-data errors at control stations over (a) NYH and (b) NB. 

Errors represent averaged magnitudes of the model-data difference over four tidal 

datums, MHHW, MHW, MLW, and MLLW. The red numbers correspond to station 

numbers listed on the first column of Tables B.1 and B.2. Color bars are in cm.. ........................19 

Figure 13. Distribution of VDatum marine grid points. Dark grey area represents water 

points populated with tidal datums and light grey area denotes those assigned with null 
viii

values. Yellow line illustrates the marine grid bounding polygon. Color lines (red, blue, 

green, and black) delineate the four VDatum bounding polygons for the New York 

Harbor, Long Island Sound, Block Island Sound, and Outer New York Bight regions. ...............22 

 

Figure 14. Tidal datum fields on VDatum marine grid, (a) MHHW, (b) MHW, (c) MLW, 

(d) MLLW, (e) MTL, and (f) DTL. Color bars are in meters ........................................................24 

Figure 15. Coverage of the LIS-NY (gray shaded area) and NYB (polygon area outlined 

by red line) VDatum areas and locations of three transects, AA', BB', CC' along which 

tidal datums from LIS-NY and NYB are compared ......................................................................25 

Figure 16.1. Comparisons of the LIS-NY and NYB MHHW along transects (a) AA', (b) 

BB', and (c) CC'. Location index represents indices of data points relative to the starting 

point (A, B, or C) of each transect. ................................................................................................28 

Figure 16.2 Comparisons of the LIS-NY and NYB MHW along transects (a) AA', (b) 

BB', and (c) CC'. Location index represents indices of data points relative to the starting 

point (A, B, or C) of each transect. ................................................................................................29

Figure 16.3 Comparisons of the LIS-NY and NYB MLW along transects (a) AA', (b) 

BB', and (c) CC'. Location index represents indices of data points relative to the starting 

point (A, B, or C) of each transect. ................................................................................................30 

Figure 16.4 Comparisons of the LIS-NY and NYB MLLW along transects (a) AA', (b) 

BB', and (c) CC'. Location index represents indices of data points relative to the starting 

point (A, B, or C) of each transect. ................................................................................................31 

Figure 17. Location of tidal benchmarks and tide stations used to compute the TSS grid ............34 

Figure 18. The TSS field within the VDatum domain. The TSS values are labeled in 

meters ....................................................................................................................................35 

LIST OF TABLES 

Table 1. Speeds, nodal factor, and equilibrium arguments of 7 tidal constituents used for 

forcing model runs .........................................................................................................................12 

Table 2. Marine Grid Parameters for New York Harbor, Long Island Sound, Block Island 

Sound, and Outer New York Bight. ...............................................................................................22 

Table 3. The root-mean-square of differences between the LIS-NY and NYB tidal datums 

along three transects .......................................................................................................................26 
ix

ABSTRACT 

An application of the vertical datum transformation software tool, VDatum, is developed 

for the Long Island Sound (LIS), Narragansett Bay, New York Harbor and New York 

Bight areas. It performs conversions between various tidal datum fields and mean sea 

level as well as between mean sea level and the North American Vertical Datum of 1988 

(NAVD88). 

 

The tidal datums fields were created using an unstructured, two-dimensional, barotropic 

hydrodynamic model, the ADvanced CIRCulation (ADCIRC) model. A triangular finiteelement grid consisting of 181,798 nodes and 333,910 cells was created for this tide 

model application. The model run was forced with seven tidal constituents (M2, S2, N2, 

K2, K1, O1, Q1) and tidal-induced water level undulations were simulated for 37 days. 

Various tidal datum fields, including mean lower low water (MLLW), mean low water 

(MLW), mean high water (MHW), and mean higher high water (MHHW), were 

computed based on water level time series from the final 30 days of the simulation. 

Model results were validated by comparing modeled and accepted datums from 123 

water level stations maintained by NOAA’s Center for Operational Oceanographic 

Products and Services (CO-OPS). Discrepancies between model results and accepted 

datums were attributed to model errors and were interpolated over the whole model 

domain using the tidal constituent and residual interpolation (TCARI) software to obtain 

a domain-wide error field for each tidal datum. The error fields were applied to the model 

results to achieve error-corrected tidal datums on the unstructured model grid. Finally, 

tidal datum fields were interpolated onto a regular VDatum grid of 0.0017 degree by 

0.0017 degree (approximately 185 m by 185 m) resolution. 

A topography of the sea surface (TSS), defined as the elevation of NAVD88 relative to 

local mean sea level (LMSL), was derived based on data from the most recent National 

Tidal Datum Epoch (1983-2001). The NAVD88-to-LMSL spatially-varying 

transformations were computed using orthometric-to-tidal datum relationships at NOAA 

tidal gauges and at tide station benchmarks. Results from both methodologies were 

coupled to create a final TSS grid using spatial interpolation techniques. 

Key Words: tides, tidal datums, VDatum, Long Island Sound, New York Bight, 

Narragansett Bay, ADCIRC, mean sea level, bathymetry, coastline, spatial interpolation, 

marine grid, North American Vertical Datum of 1998 
x
1

1. INTRODUCTION 

NOAA’s National Ocean Service (NOS) is developing a software tool called VDatum to 

transform elevation data among approximately 30 vertical datums (Milbert, 2002; Parker, 

2002; Myers et al., 2005). Once VDatum has been established for a region, data can be 

incorporated into integrated bathymetric-topographic digital elevation models (DEMs) 

for use in coastal GIS applications (Parker et al., 2003). VDatum allows bathymetric and 

topographic data to be integrated through its inherent orthometric, ellipsoidal, and tidal 

relationships. 

To be applicable over coastal waters, VDatum requires spatially-varying fields of the 

tidal datums. These include mean higher high water (MHHW), mean high water (MHW), 

mean low water (MLW), mean lower low water (MLLW), mean tide level (MTL) and 

diurnal tide level (DTL). The tidal datums are combined with orthometric and ellipsoidal 

models, and relationships between these groups of vertical datums are established as 

input to the VDatum software. Tidal datum fields have previously been produced by NOS 

for many U.S. coastal areas: Tampa Bay (Hess, 2001), coastal southern Louisiana (Hess 

et al., 2004), the New York Bight (Hess, 2001), central coastal California (Myers and 

Hess, 2005), Delaware Bay (Hess, 2003), Puget Sound (Hess and Gill, 2003), and the 

Calcasieu River from Lake Charles to the Gulf of Mexico (Spargo and Woolard, 2005). 

As a continuing effort in support of the VDatum development, the present study focuses 

on resolving tidal datum fields and the Topography of Sea Surface (TSS) for an area over 

the southern New England shelf, encompassing the Long Island Sound (LIS), 

Narragansett Bay (NB), and New York Bight (NYB) regions. Figure 1 displays a map for 

the region of interest. In the figure, the red lines represent the MHW coastline, and the 

green line denotes locations 25 nautical miles offshore. Tidal datums for VDatum are 

usually computed between the MHW shoreline and the 25 nautical mile offshore limit. 

This report describes the creation of the tidal datum and TSS fields in support of VDatum 

for the LIS, NYB, and NB areas. Computed tidal datums include MHHW, MHW, MLW, 

MLLW, MTL, DTL and local mean sea level (LMSL). The topography of the sea surface 

is the elevation of the North American Vertical Datum of 1988 (NAVD88) relative to 

LMSL. Creation of VDatum begins with numerically simulating water level time series 

with an unstructured two-dimensional hydrodynamic model. The tidal datums were 

derived from the modeled time series and error corrections were made using computed 

model-data differences. A regular VDatum marine grid was created and populated with 

corrected tidal datums. Finally, for the same marine grid, the NAVD88-to-LMSL 

differences were derived by fitting a surface to the observed orthometric-to-tidal datum 

relationships at NOAA tidal gauges and benchmarks. 

This technical report is organized as follows: After an introduction in Section 1, Section 2 

discusses bathymetric, coastline and tidal datum data gathered to drive the hydrodynamic 

model and verify its results. Section 3 details the tidal simulation procedures, including 

an introduction of the hydrodynamic model, its setup, result validation, and error 

corrections. Section 4 discusses the creation of a regular VDatum marine grid required 

for the VDatum software tool and its population with error-corrected model datums. In 
2

Section 5, creation of the TSS for the area is described. Finally, a summary is given in 

Section 6. 

 Figure 1. Map of the Long Island Sound, New York Bight, and Narragansett 

 Bay area. Red lines show the MHW coastline, and the green line denotes a distance 

25 nautical miles offshore. 

Hudson 

River 

Narragansett 

Bay

New York

Harbor

Block 

Island 

Housatonic 

River

Connecticut 

River

New York 

Bight

Montauk 

Point 

Long Island Sound
3

2. COASTLINE, BATHYMETRIC, AND WATER LEVEL DATA 

Knowledge of the spatial distribution of tidal datums is necessary for developing VDatum 

(Milbert and Hess, 2001). NOAA’s Center for Operational Oceanographic Products and 

Services (CO-OPS) computes tidal datums using water level time histories available from 

their National Water Level Observation Network (NWLON). To compute the spatiallyvarying fields of tidal datums between these stations, tidal models can be used to simulate 

water level time histories from which modeled tidal datums may be computed. 

Hydrodynamic models are capable of resolving the spatial variability of tidal datum fields 

with flexible resolutions (Myers, 2001; Spargo and Woolard, 2005). To setup the tide 

simulations, coastline data are required for delineating land-water boundaries. In 

addition, bathymetric data are needed to provide the model grid bathymetry. Tidal datums 

computed by CO-OPS from observations are also required to verify the model results and 

provide corrections in producing final tidal datum fields. 

2.1. Digital Coastline 

The mean high water shoreline is used as the coastline to delineate the land-water 

boundaries (Parker, 2002). In the present study, the MHW shoreline was initially based 

on the digitized data of the Extracted Vector Shoreline (EVS) from the NOS Office of 

Coast Survey (OCS). However, when compared to NOAA nautical chart MHW 

shorelines, this data set demonstrated evident errors at certain nearshore marshland areas. 

By employing computer-aided techniques, erroneous segments of the EVS coastlines 

were corrected, so that the refined coastline matches the MHW coastline illustrated on 

geo-referenced, digital nautical charts. A commercial software package called Surfacewater Modeling System (SMS) was used to implement the correction. First, both the 

nautical charts and the EVS data were loaded into the SMS environment and contrasted 

with each other through the computer display. Wherever the two do not match, the EVS 

was judged to be incorrect. The corresponding segment of coastline was digitized 

according to the chart MHW coastline and the erroneous EVS coastline was replaced by 

the chart coastline. In Figure 1, red lines illustrate the final corrected coastline. The 

coastline specification was expressed as (longitude, latitude) pairs and possessed a 

precision up to the 6-th decimal point in degree (about 0.1 m). 

2.2. Bathymetric Data 

Bathymetric data used in this study were from two sources: a NOS soundings database 

and the NOAA Electronic Navigational Charts (ENCs) bathymetry. The former were 

from the NOS/OCS hydrographic database maintained at the National Geophysical Data 

Center (NGDC) and the latter were based on the 2004 editions of the NOAA ENCs. The 

NOS sounding data included surveys conducted between 1930 and 2000. The datums 

were referenced to either MLW or MLLW, depending on the years of data collections. 

Figure 2 shows the survey years and locations. Figure 3 illustrates the spatial distribution 

of the ENC data points. It was known that the ENC data were referenced to both MLW 

and MLLW. However, available documents do not ensure any feasible way to distinguish 

the two for individual data points. Therefore, the whole ENC data set was treated as 
4

being solely referenced to MLLW. Tables A.1 and A.2 list sources of bathymetry data 

and the corresponding NOAA survey standards. 

Comparing Figures 2 and 3, it is evident that in most locations, NOS soundings possess a 

higher spatial distribution density than the ENC data. In some areas the two are both 

available. However, neither of them provides complete coverage for the whole study 

area. Blending the two data sets turned out to be necessary for a better regional coverage. 

For areas where both soundings and ENC data were available, soundings were used first, 

considering their superior spatial resolution. It is noted that even the blended data set left 

certain nearshore areas along the north LIS coast uncovered. NOAA nautical chart 

bathymetry was then manually digitized using computer-aided techniques to compensate 

for the missing coverage. Since both the ENC and manually digitized bathymetries were 

grounded in nautical chart data, they were then blended to form one data set and hereafter 

referred to as the ENC bathymetry without differentiation. 

1990 - 2000 

1930 - 1939 

1940 - 1949 

1950 - 1959 

1960 - 1969 

1970 - 1979 

1980 - 1989 

Dates of Surveys 

Figure 2. Dates and locations of NOS sounding surveys. 
5

2.3. Tidal Datum Data 

Tidal datums from CO-OPS water level stations are available online (Hess and Spargo, 

2005) and were used to verify and correct model results. Many stations in the region of 

interest are located within either embayments or near obstructions not represented in the 

present model grid (Section 3.2), or at upper reaches of riverine regions where datums 

exhibit strong seasonal variability. Observations at these stations were determined to be 

unsuitable for validating model results and were thus discarded. This resulted in 123 

stations actually used for validating and correcting the model results. Tables B.1 and B.2 

in Appendix B list the station and tidal datum information. 

It is indicated in Table B.1 that tidal datums at the 123 stations correspond to different 

national tidal epochs (NTDE). In the present project, tidal datums of all stations are 

treated as of the same quality without distinction. This is justified by comparing tidal 

datums at 72 stations with both 1960-1978 and 1983-2001 epochs data available. Table 

B.3 in Appendix B list mean tidal ranges of different epochs, their ratios, differences, and 

percentages of the differences. Of all the stations, the averaged ratio is 0.99; the averaged 

absolute difference is 0.013 m, with differences at each individual station ranging from 

0.0 cm to 3.8 cm; the average percentage of differences is 1.0%. Tidal datums from 

Figure 3. Spatial distribution of the ENC bathymetric data. 
6

epochs before 1983-2001 are therefore deemed to be reliable and used in model-data 

error corrections. 
7

3. TIDAL DATUM SIMULATION 

3.1. Hydrodynamic Model 

The ADCIRC model (Westerink and Luettich, 1993; Luettich et al., 1999) was employed 

to model water level time histories and derive tidal datum fields. The ADCIRC model is a 

prognostic, unstructured grid, hydrodynamic circulation model. It simulates tides by 

solving the shallow water equations and has been proved to be valid for modeling tides in 

various oceanic environments from open oceans to coastal and estuarine waters (Luettich 

et al., 1999; Mukai et al., 2002; Myers 2005). The ADCIRC model provides a variety of 

options for users to specify various aspects of tidal dynamics and execution modes. For 

instance, the model run could be in either 2- or 3-dimensonal modes, serial or parallel 

execution dependent on machine infrastructures, linear or quadratic bottom friction 

formulations with constant or variable friction coefficients, etc. 

In the present study, model parameters were set up to solve the shallow water equations 

in Two-Dimensional Depth-Integrated (2DDI) mode with finite amplitude and 

convection terms. Lateral viscosity was set as a constant, 5.0 m s-2, throughout the model 

domain. A quadratic friction scheme with spatially-varied coefficient (Cd) was specified 

to calculate bottom friction. Multiple test runs were conducted to test various Cd values 

(Figure 4) in an attempt to mitigate model-data discrepancy of tidal datums. In general, 

final adopted Cd increased eastward throughout LIS from 2.0×10-3 to 3.2×10-3; 

Cd=3.2×10-3 was used across the Block Island Sound and Rhode Island Sound (RIS); in 

the NB area Cd varied from 3.2×10-3 at RIS to 2.1×10-3 near the upper bay; Cd was 

3.0×10-3 throughout NYB and dropped to 2.1×10-3 near the New York Harbor (NYH) 

area. The values corresponded to an optimal model-data agreement. 

A model time step of 1.0 second was used to ensure numerical stability in the 

simulations. A 37-day model run was conducted. The model was ramped up for the first 5 

days with a hyperbolic tangent function. At each grid node, water level time histories 

were recorded at 6-minute intervals for the last 30 days. The parallel version was adopted 

and the model run utilized 72 processors of the JET computer at NOAA’s Earth System 

Research Laboratory’s High Performance Computing System. It took approximately 18 

hours to complete the 37-day simulation. 
8

Figure 4. Spatially variable bottom friction coefficient (Cd) employed 

 in model computation. 

3.2. Model Grid 

The model domain covers coastal waters from east of Narragansett Bay south to the 

coast of New Jersey, encompassing LIS, NB, NYH, and NYB (Figure 5). The ocean 

boundary is set approximately along the 90 meter isobath. A high-resolution, 

unstructured grid with 333,910 triangular elements and 181,798 nodes was created to 

represent the domain up to the MHW shoreline. Element spacing for the grid ranges from 

around 25 m in nearshore waters to 5.5 km in the open ocean. In general, finer elements 

were created for nearshore areas compared to those in deep waters, so as to accurately 

resolve fine coastline features and reflect bathymetry variability. Figures 5a-c show 

close-up views of the grid at three domain sections near NYH, NB, and LIS, respectively. 

It is noted that lagoons along south coast of Long Island were not represented in the 

present grid. This is because tidal datums in these lagoon areas were not the interest of 

this project and a previous study (Swanson, 1976) indicates that their existence does not 

exert evident influence on tidal fields in adjacent coastal waters, probably due to the very 

limited inlet cross-sectional area for tidal waves to pass through. Therefore, the lagoon 

areas were excluded from the present modeling consideration.

Cd 
9

Figure 5. Finite element grid for the entire model domain. Blue line represents the 

model open boundary. Numbers labelled along the boundary denote the node 

identification numbers of adjacent red dots.

1 

10 

20

30 

40

60 

50

70 

80 

90

100

110
10

Figure 6. Zoom of the model grid near (a) New York Harbor, (b) Narragansett Bay, 

and (c) Long Island Sound. 

3.3. Bathymetry for the Model Grid 

The bathymetric data described in Section 2.2 were used to specify model grid 

bathymetry. Note that NOS soundings and ENC data were of different spatial resolution 

and coverage. As for the soundings themselves, bathymetry may be referenced to either 

MLW or MLLW. Hence, they were categorized into two groups and applied to the grid 

separately. The bathymetric data sets were grouped into three categories: (1) MLLW 

NOS soundings (2) MLW NOS soundings, and (3) MLLW ENC data. The three groups 

were interpolated onto the model grid separately and this resulted in three meshes 

corresponding to the aforementioned three bathymetric data sets. 

The algorithm used for populating the three meshes was the same. For a given node, 

bathymetric data located within the area delineated by that node’s surrounding elements 

were searched and interpolated onto the node through inverse-squared distance 

interpolation. Since element size changes throughout the model domain, the searching 

ranges for bathymetric data points vary from node to node. As the element size is smaller 

in shallower water, bathymetry for nodes near the coastline were from more locally 

distributed data points than those in deep waters. 

As none of the three data sets provided complete coverage of the model domain, each of 

the three meshes left numerous unpopulated nodes. The three meshes were then 

(c) 

(a) (b)
11

combined to obtain a more complete coverage. The two NOS sounding meshes were 

merged first. For each node with bathymetry available in both meshes, an arithmetic 

average of the two values was taken; for those with bathymetry available only in either of 

the two, the available one was used. It is noted that the two sets of NOS sounding mesh 

bathymetries were referenced to different datums, either MLLW or MLW depth. 

Therefore, soundings referenced to MLW datum were first adjusted by adding a 

difference, HMLLW-MLW= MLLW-MLW, to ensure that both meshes were using the same 

MLLW depths. The HMLLW-MLW varies throughout the domain. However, before the 

initial model run, the spatial variability was unknown. It was thus initiated with an 

estimated constant value of 0.06 m, which approximated an average HMLLW-MLW over all 

CO-OPS observations in the LIS area. This constant HMLLW-MLW was later updated by a 

spatially-varied one from model outputs. After merging the two sounding meshes, the 

ENC mesh was then incorporated to fill in unpopulated nodes. However, even after 

merging the three meshes, there still remained many nodes without valid bathymetry. 

Bathymetry of these nodes were interpolated from adjacent nodes through nearestneighbor extrapolation. 

The hydrodynamic model implementation requires bathymetry referenced to MSL. It was 

necessary to adjust the reference datum of the grid bathymetry from MLLW to MSL. It 

was accomplished by iteratively updating MLLW-MSL field using both observational 

data and model results from a series of simulations. Since the MSL-MLLW difference 

was unknown prior to model runs, an offset of MSL-MLLW=0.8 m was applied on the 

whole grid as an initial estimate based on observed datums at CO-OPS water level 

stations in the area. Following each model run, new sets of tidal datum fields were 

derived and used to update aforementioned MLW-MLLW and MSL-MLLW fields. In 

pursuit of model result convergence, multiple runs were made until invariant values of 

four datums (MHHW, MHW, MLW, and MLLW) were achieved. In the present study, 

three iterations were made to satisfy a convergence criteria of 0.1 cm in the difference of 

datums from subsequent simulations. Figure 7 displays the final bathymetry used by the 

hydrodynamic model. 

3.4. Boundary Forcing and Model Run 

Barotropic tidal elevations were simulated with the ADCIRC model. The model was 

forced with harmonic constants of seven astronomical tidal constituents (K1, O1, Q1, M2, 

S2, N2, and K2) on the model’s open boundary. At each boundary node, water level was 

determined according to 

( ) cos( [ ] ), { , , , , , , } 1 1 1 2 2 2 2

7

1

ς t f A t V u κ i K O Q M S N and K

i

  i i i  o  i  i   , 

where  represents the instantaneous water level relative to model zero, t is the time, i

denotes one of the seven constituents, fi is the nodal factor, Ai is the constituent 

amplitude, i is the constituent speed, [Vo+u]i represents the equilibrium argument at 

time zero, and i is the Greenwich epoch. Table 1 lists values of i, fi, and [Vo+u]i used 

in the simulation; for the latter two, the values correspond to those of mid-1992, at 
12

which M2 f approximates unity. The Ai and i values were interpolated from results of a 

Western North Atlantic Ocean tidal model (WNATM) (Meyers, unpublished 

manuscript). 

Figure 7. Model grid bathymetry relative to MSL. Color bar is in meters. 

 Table 1. Speeds, nodal factors, and equilibrium argument of seven tidal 

 constituents used for forcing model runs 

Constituent Speed (10-5 s-1) 

i 

Nodal Factor 

fi 

Equilibrium 

Argument (degrees) 

[Vo+u]i

K1 

O1 

Q1 

M2 

S2

N2

K2 

7.2921158358 

 6.7597744151 

6.4958541129 

14.0518902509 

14.5444104333 

13.7879699487 

14.5842317201 

1.030 

1.024 

1.024 

1.000 

1.000 

1.000 

1.016 

18.70 

78.70 

326.2 

101.3 

0.000 

348.8 

217.6 
13

Some adjustments were made on the M2 amplitudes at nodes toward NB to improve 

model-data agreement at stations near upper NB. Figure 8 shows the two data sets, one 

(blue circles) representing the direct interpolation of the WNATM tidal database and the 

other (red triangles) displaying those after the adjustment. The adjustment starts from 

nodes near the middle of the open boundary. The change of amplitude gradually increases 

toward NB and reaches a maximum of around 5 cm on nodes close to the mouth of NB. 

Figure 8. M2 amplitudes on the model open boundary nodes. Blue circles represent those 

interpolated from WNATM and red triangles denote those after adjustment. Locations of 

the open boundary nodes are illustrated in Figure 5. 

3.5. Results 

Water level time series from the ADCIRC simulation were recorded at 6-minute intervals 

at each grid node. They were passed into the FORTRAN program lv3.f (Hess, 2001) to 

calculate the following tidal datum fields: MSL, MHHW, MHW, MLW, and MLLW. 

The computed datums were referenced to the model zero (MZ). The latter four were then 

adjusted to be referenced to the MSL field. Henceforth, references to each of the tidal 

datums shall imply this adjusted value relative to MSL. Note that MTL is defined as the 

algebraic average of MHW and MLW, and DTL is the algebraic average of MHHW and 

MLLW. The two fields were not computed until error-corrected MHHW, MHW, MLW, 

and MLLW fields were obtained (Section 4.2). For reference, the modeled MSL field is 

displayed in Figure 9. Note that it simply represents the difference between the averaged 

model water level time histories and MZ. 
14

Figure 9. Model derived MSL field relative to MZ (units are cm). 

Figures 10a-d display the MHHW, MHW, MLW, MLLW fields, respectively. Modeled 

datum fields demonstrate good agreement with previously published results in both 

spatial variability patterns and magnitudes (Swanson, 1976). As expected, the four tidal 

datum fields exhibit a similar spatial pattern. In LIS, tidal range is enhanced by 

approximately fourfold from about 0.7 m near Block Island to 2.2 m at the western end of 

LIS. In NB, the tidal range shows much smaller magnitude and demonstrates less severe 

spatial variability compared to that in LIS. Across the Bay, tidal range lies between 1.2-

1.4 m, except for near its upper reaches where the range could be as high as 1.6 m. In 

New York Harbor, tidal range remains quite homogeneous, around 1.2 m. The NYB is 

located in relatively open and deep waters. The average tidal range in the central Bight is 

about 1.1 m. Along the south coast of Long Island, the range drops from 1.2 m near NYH 

in the east to 0.7 m near Montauk Point in the west. 
15

Figure 10. Tidal datum fields, (a) MHHW, (b) MHW, (c) MLW, and (d) MLLW relative 

to MSL, as computed by the hydrodynamic model. Color bars are in meters. 

3.6. Verifications and Error Corrections 

To verify model results, simulated tidal datums were compared with those from 123 COOPS tidal gauge observations. For each datum, model results were interpolated onto the 

CO-OPS station locations using an inverse-squared distance algorithm. 

Figures 11a-d display model-data contrasts for MHHW, MHW, MLW, and MLLW, 

respectively. In general, there is good model and data agreement. Over the 123 stations, 

average differences between the modeled and observed values are 2.3 cm, 2.2 cm, 3.4 

cm, and 2.6 cm for MHHW, MHW, MLW, and MLLW, respectively. For each individual 

station, the averaged absolute difference (|Avg|) between the model and observations over 

the four datums is examined and is displayed as color-coded symbols in Figures 12a-d. 

Figure 12a displays overall station distributions and Figures 12b-c show zoomed views 

near LIS, NYH, and NB, respectively. Magnitudes of discrepancy are smaller than 6.0 cm 

at over 90% of stations. For the remaining 10%, they are smaller than 7.2 cm except for 

one station (station ID number: 8458022) at (71.75o

W, 41.32oN), which gives |Avg|=10.4 

cm; see the red color-coded symbol in Figure 12b. 

(a) (b) 

(c) (d) 
16

Figure 11. Comparisons of the modeled (1) MHHW, (2) MHW, (3) MLW, and (4) 

MLLW datums against observations. 

The relatively large model-data discrepancy at this station may result from either model 

errors or relatively low accuracy of observation data. According to NOS (2003), error 

magnitudes of CO-OPS tidal datum data varies with duration of tidal gauge 

measurements. For those less than 4 months, data accuracy may only be ensured to be 

around 4 cm. Inventory for station 8458022 indicated that water level observations 

spanned only about a 2-month period. Therefore, the apparent model errors could be 

attributed to possible inaccuracy inherited in the observational data. 

(a) (b)

(c) (d)
17

Figure 12.1. Color-coded model-data errors at control stations over (a) the whole 

domain and (b) LIS. The errors represent averaged magnitudes of the model-data 

difference over four tidal datums: MHHW, MHW, MLW, and MLLW. The red 

numbers correspond to station numbers listed on the first column of Tables B.1 and 

B.2. Color bars are in cm. 

(a) 

(b) 
18

(a) 

(b) 

Figure 12.2. Color-coded model-data errors at control stations over (a) NYH, and (b) 

NB. The errors represent averaged magnitudes of the model-data difference over four 

tidal datums: MHHW, MHW, MLW, and MLLW. The red numbers correspond to 

station numbers listed on the first column of Tables B.1 and B.2. Color bars are in cm. 
19

The model-data differences at the control stations show the pattern of model errors over 

the whole model domain. To correct errors on the entire model grid, spatial distributions 

of the error fields need to be calculated. This was achieved via the tidal constituent and 

residual interpolation (TCARI) technique (Hess, 2001; Hess, 2002). TCARI spatially 

interpolates the error fields on each grid node from values at a number of individual 

control stations by solving Laplace’s equation. TCARI has been developed for both 

structured and unstructured model grids at CSDL, and the unstructured version was used 

in this study. After applying TCARI, the error fields for MHHW, MHW, MLW, and 

MLLW were derived, which matched the model-data difference at the control stations. 

The modeled tidal datum fields were then corrected by subtracting the interpolated errors. 

Figures C.1a-d display the four corrected datum fields on the entire model grid. 

Note that the other two tidal datum fields, MTL and DTL, were produced in a different 

way. They were derived from the four corrected datums by taking the arithmetic averages 

between MHW and MLW and between MHHW and MLLW, respectively. 
20
21

4. CREATION AND POPULATION OF THE MARINE GRID 

4.1. Creation of VDatum Marine Grid 

The VDatum software uses tidal datum transformations defined on a regular grid (Hess 

and White, 2004). Hence, it is necessary to interpolate the tidal datum fields from the 

unstructured finite-element grid onto an equally-spaced VDatum marine grid. 

Marine grid points were categorized as either water points (darker gray area in Figure 13) 

or land points (lighter gray area in Figure 13). The water points are to be populated with 

valid tidal datum values and the land points are to be specified with null values. To create 

and populate the marine grid, a high-resolution coastline and a bounding polygon were 

used. The coastline (see Section 2 and Figure 1) delineated the land-water boundaries. A 

marine grid bounding polygon (yellow line in Figure 13) was created to guide the 

selection of the water points as well as the population of tidal datum fields. The marine 

grid (Figure 13) was created using the FORTRAN program vgridder5.f. 

Considering the limitation of the VDatum software on the maximum manageable file 

size, the VDatum marine grid was further divided into four sections, namely New York 

Harbor, Long Island Sound, Block Island Sound, and Outer New York Bight, 

respectively (Figure 13). Each section corresponds to a rectangular region in geographic 

coordinates. Marine grid points are equally spaced within each region. For a point in the 

i-th row and j-th column relative to the point of origin (longitude0, latitude0) at the 

region’s southwest corner, its location (longitude_i, latitude_j) is defined as, 

Longitude_i = longitude0 + (i-1)×del_lon, i=1, ..., N_lon 

Latitude_j = latitude0 + (j-1) ×del_lat, j=1, ..., N_lat 

where del_lon, and del_lat denote separation between adjacent points along the eastward 

and northward directions, respectively; N_lon and N_lat represent, respectively, the 

longitude and latitude dimensions of the raster data set. It is noted that the del_lon and 

del_lat are prescribed parameters representing the expected grid resolutions. The 

coordinates at the rectangular region’s northeast corner (longitude1, latitude1) are derived 

as 

longitude1 = longitude0 + (N_lon -1)×del_lon 

latitude1 = latitude0 + (N_lat -1) ×del_lat 

Table 2 lists the parameters used to define the marine grids of the above four sections. 
22

Figure 13. Distribution of VDatum marine grid points. Dark grey area represents water 

points populated with tidal datums and light grey area denotes those assigned with null 

values (i.e., land). Yellow line illustrates the marine grid bounding polygon. Color lines 

(red, blue, green, and black) delineate the four VDatum bounding polygons for the New 

York Harbor, Long Island Sound, Block Island Sound, and Outer New York Bight 

regions. 

 Table 2. Marine Grid Parameters for New York Harbor, Long Island Sound, Block 

Island Sound, and Outer New York Bight. 

 

 

 Region Longitude0 

(degree) 

Latitude0 

(degree) 

del_lon 

(degree) 

del_lat 

(degree) N_lon N_lat 

RA New York 

Harbor 

285.6341 

(-74.3659) 39.3553 0.0017 0.0017 628 1557 

RB Outer New 

York Bight 

286.3005 

(-73.6995) 39.3553 0.0017 0.0017 1589 674 

RC Long Island 

Sound 

286.3005 

(-73.6995) 40.5011 0.0017 0.0017 706 785 

RD Block Island 

Sound 

287.5007 

(-72.4993) 40.5011 0.0017 0.0017 883 785 

New York 

Harbor (RA) 

Long Island

Sound (RC)

Outer New 

York Bight (RB)

Block Island 

Sound (RD) 
23

4.2. Population of VDatum Grid with Tidal Datums 

Tidal datums on the Vdatum marine grid were populated by interpolating TCARIcorrected model values (Section 3.6) using the algorithm of Hess and White (2004). 

Datums on each VDatum marine grid point were calculated by averaging or linearly 

interpolating those within a user-specified searching radius or the closest user-specified 

number of points. In the present case, the interpolation was accomplished using the 

FORTRAN program vpop10.f. It populates marine points differently depending on 

whether the point is inside/outside of ADCIRC grid elements. If the point is inside an 

element, datums were calculated by interpolating values from the element’s three 

vertices; if the point lies outside of any elements, datums were computed using the 

inverse distance weighting of the closest two node values. Compared with tidal datums 

from 123 observation stations, maximum errors are 1.8 cm for MHHW, 1.8 cm for 

MHW, 1.4 cm for MLW, and 1.4 cm for MLLW. 

Figures 14a-f display the populated MHHW, MHW, MLW, MLLW, MTL, and DTL on 

the VDatum marine grid. Tidal datum fields demonstrate significant spatial variability. 

For the LIS area, tidal range (MHW-MLW) was around 0.8 m at the Sound’s eastern end 

and increased to nearly 2.4 m at the western end near the East River. In the NB region, 

tidal range increased by twofold from about 1.2 m at the Bay mouth to 2.4 m in the upper 

Bay. Compared to the former two, the NYH region seems to belong to a different tidal 

regime. The tides demonstrated quite homogeneous tidal datum fields with a tidal range 

of about 1.6 m. 
24

 Figure 14. Tidal datum fields on the VDatum marine grid, (a) MHHW, (b) MHW, 

(c) MLW, (d) MLLW, (e) MTL, and (f) DTL. Color bars are in meters. 

(a) (b) 

(c) (d) 

(e) (f) 
25

4.3. Comparison with Previous Results 

Tidal datum fields for the Long Island Sound, Narragansett Bay, New York Harbor, New 

York Bight areas (referred to as LIS-NY in the following) were developed in this project. 

It is noted that a portion of the present domain overlaps with that of a previously 

developed New York Bight (NYB) VDatum project (Hess, 2001). Figure 15 illustrates 

the two domains. In the figure the shaded area represents LIS-NY marine grid points and 

the red line denotes the NYB domain. The two domains overlap over outer New York 

Bight and Lower Bay; in the figure, this overlap area is shown as the shaded area west of 

transect BB' and north of transect CC'. 

Figure 15. Coverage of the LIS-NY (shaded area) and NYB (polygon area outlined by 

red line) marine grid areas and locations of three transects, AA', BB', CC' along which 

tidal datums from LIS-NY and NYB are compared. 

Since datum fields for the two regions were developed separately through different 

approaches, they are not necessarily matched seamlessly along CC'. Existence of any 

significant discrepancy would be physically unrealistic, and would lead to VDatum not 

being seamless across these regions. Hence it is necessary to compare the two sets of 

results and determine how to match the two products.

A'

A

C 

C' B 

B' 
26

Three characteristic transects (AA', BB', and CC' in Figure 15) are selected for the 

comparison. Transect AA' corresponds to locations near the entrance to the Lower Bay 

west of New York Bight, and BB' and CC' represent, respectively, the southern and 

eastern borders of the NYB marine grid. Comparisons along the three transects should 

provide insight into the level of agreement between the LIS-NY and NYB results along 

their west, east, and south boundaries, respectively. 

Along each transect, locations where marine grid points from both LIS-NY and NYB 

coincide were selected as locations for comparison (Figure 15). The points are roughly 

equally-distanced. Four tidal datums (MHHW, MHW, MLW, and MLLW) of LIS_NY 

and NYB are separately interpolated onto these locations. Figures 16.1-4 displays, 

respectively, MHHW, MHW, MLW, and MLLW along the three transects. Table 3 lists 

the root mean square (rms) of the datum differences between the LIS-NY and NYB 

regions. Along the three transects, MLLW demonstrates the best match of the four 

datums, with rms differences between 0.786 cm (transect CC') and 2.635 cm (transect 

AA'); the other three datums exhibit similar degree of agreement but slightly greater rms 

differences of between 1.83 cm and 3.55 cm. 

Table 3. The root mean square of differences between the LIS-NY and 

NYB tidal datums along three transects. 

Transects MHHW 

(cm) 

MHW 

(cm) 

MLW 

(cm) 

MLLW 

(cm) 

AA' 2.34 3.04 2.98 1.25 

BB' 3.20 3.01 3.55 2.64 

CC' 1.83 2.58 1.97 0.79 

On each plot of Figure 16, the abscissa represents node numbers counted from the 

beginning points of the three transects (Figure 15), i.e., A, B, or C respectively for 

transects AA’

, BB’, and CC’. As indicated in Figure 16.1-4, datum differences are evenly 

distributed with gradual variation along transects AA' and CC', as well as most of transect 

BB'. For the latter, datum differences exhibit dramatic changes and display significant 

magnitudes close to its north end (Montauk Point). The maximum difference for MHHW, 

MHW, MLW, MLLW are 10.0 cm, 9.2 cm, 6.6 cm, and 8.6 cm, respectively. The reason 

for the evidently large differences could be associated with different degrees of proximity 

of the two model coastlines to the true coastline near the Point. Large coastline curvature 

near the Point heavily affects tidal fields and introduces dramatic spatial variability in 

tidal datum fields (Figure C.1). Therefore, even a small discrepancy in the two model 

coastlines can result in significant differences in the resulting tidal datum fields. 

Comparison along transect CC is of major interest, since of the three transects only CC' 

represents an intersection between a LIS-NY boundary and the NYB domain. Datum 

matches along CC' is crucial for a seamless transition between the two domains. In fact, 

the LIS-NY and NYB datums demonstrate good agreement along CC. Maximum 

magnitudes of MHHW, MHW, MLW, MLLW differences are 2.93 cm, 3.58 cm, 3.84 

cm, and 2.20 cm, respectively. The rms differences for the same four datums are 1.83 cm, 

2.58 cm, 1.97 cm, and 0.79 cm, respectively. 
27

It is noted that the NYB results are planed to be phased out. For the overlapping area 

north of transect CC' (Figure 15), the present LIS-NY results will apply. VDatum for the 

rest of the NYB area (south of transect CC') will be updated by those from a combined 

Chesapeake Bay and Delaware Bay (CHK-DEL) project currently under development 

(Yang, et al., unpublished manuscript). Note that in developing the CHK-DEL VDatum, 

information of the LIS-NY tidal datums along their common border (transect CC') will be 

incorporated into the TCARI (Section 3.6) adjustment procedures (Yang, et al., 2003) and 

therefore a seamless datum match across CC’ will be obtained. The potential tidal datum 

mismatches demonstrated in Figure 16 will be avoided. 
28

Figure 16.1. Comparisons of the LIS-NY and NYB MHHW along transects (a) AA', (b) 

BB', and (c) CC'. Location index represents indices of data points relative to the starting 

point (A, B, or C) of each transect. 

Transect AA' 

Transect BB' 

Transect CC' 

Δ NYB 

○ LIS-NY 

(a) 

(b) 

(c) 
29

Figure 16.2. Comparisons of the LIS-NY and NYB MHW along transects (a) AA', (b) 

BB', and (c) CC'. Location index represents indices of data points relative to the starting 

point (A, B, or C) of each transect. 

Transect AA' 

Transect BB' 

Transect CC' 

Δ NYB 

○ LIS-NY 

(a)

(b)

(c)
30

Figure 16.3. Comparisons of the LIS-NY and NYB MLW along transects (a) AA', (b) 

BB', and (c) CC'. Location index represents indices of data points relative to the starting 

point (A, B, or C) of each transect. 

Transect AA' 

Transect BB' 

Transect CC' 

Δ NYB 

○ LIS-NY 

(a)

(b)

(c)
31

Figure 16.4. Comparisons of the LIS-NY and NYB MLLW along transects (a) AA', (b) 

BB', and (c) CC'. Location index represents indices of data points relative to the starting 

point (A, B, or C) of each transect. 

Transect AA' 

Transect BB' 

Transect CC' 

Δ NYB 

○ LIS-NY 

(a)

(b)

(c)
32
33

5. TOPOGRAPHY OF THE SEA SURFACE 

The Topography of the Sea Surface (TSS) is defined as the elevation of the North 

American Vertical Datum of 1988 (NAVD88) relative to local mean sea level (LMSL). 

The TSS field is created by combining datum values at NGS benchmark locations with 

model results. The location of tide gauges and tidal benchmarks used in generating the 

TSS are illustrated in Figure 17. At each NGS benchmark location, there is a set of 

TBMdatum values, which is the elevation at the Tidal Benchmark of a datum relative to 

MLLW (i.e., Datum – MLLW). Table E.2 in Appendix E lists the differences for each 

tidal datum at NGS benchmarks. Also, from the four tidal datum grids (see Section 4), we 

have a set of VDdatum values, which are the difference between the tidal datum and MSL 

(i.e., Datum – MSL). 

For the first step, we compute four residuals, which are defined separately for MHHW, 

MHW, MLW, and MLLW as: 

Rdatum = TBMnavd88 – TBMdatum + VDdatum

Note that the VD values are interpolated to the location of the benchmark. The four 

residuals at the benchmark are averaged to produce the mean. Note that this mean is an 

estimate of the quantity MSL – NAVD88. 

Next, a gridded sea surface topography field is generated. The mean residuals at all 

benchmarks are merged with (NAVD88-MSL) values at CO-OPS’ water level stations to 

produce input data for contouring. A mesh covering the entire area of benchmarks and 

water level stations with a spatial resolution similar to that of the tidal datum marine grid 

is created (see Figure 18). Breaklines are inserted to represent the influence of land. A sea 

surface topography field is generated using the Surfer© software’s minimum curvature 

algorithm to create a surface that honors the data as closely as possible. The maximum 

allowed departure value used was 0.0001 meters. To control the amount of bowing on 

the interior and at the edges of the grid, an internal and boundary tension value of 0.3 was 

utilized. Once the gridded topography field has been generated, null values are obtained 

from the marine tidal grids and are inserted to denote the presence of land. 

Then a set of ‘Delta’ values are computed. Delta represents the difference between the 

observed tidal datum (see Table E.2 in Appendix E for a list of observation stations) and 

the datum as computed by the gridded fields. If S represents the value of the quantity 

NAVD88 – MSL obtained from the sea surface topography grid, then Delta (D) for each 

tidal datum is computed as: 

-Ddatum = TBMnavd88 – TBMdatum + VDdatum - S 

The averaged Delta at each benchmark should be less than 0.01 m. If it is not, the input 

data and grids are checked, appropriate changes are made, and the Deltas are recomputed 

until the criterion is met. This process resulted in the TSS field shown in Figure 18. 
34

Tables E.1 and E.2 in Appendix E provide comparison of derived LIS TSS with 

observations and error analysis results, respectively. 

 

 Figure 17. Location of tidal benchmarks and tide stations used to compute the Long 

 Island Sound TSS grid. 

Figure 17. Location of tidal benchmarks and tide stations used to compute the TSS 

grid. 
35

Figure 18. The TSS field withhin the VDatum domain. The TSS values are labeled in 

meters. 
36
37

6. SUMMARY 

In support of development of the national vertical datum software tool, VDatum, tidal 

datum and TSS fields for an area covering the Long Island Sound, Narragansett Bay, and 

New York Bight were developed in this study. Tidal datum fields were created by 

simulating tidal level time histories using the ADCIRC hydrodynamic model. The model 

domain was represented with an unstructured, triangular-element grid of 181,798 nodes 

and 333,910 elements. ADCIRC simulations were forced with harmonic constants of 7 

tidal constituents on the model’s open ocean boundary. At each grid node, a water level 

time series spanning 30 days was used to compute four tidal datums, MHHW, MHW, 

MLW, and MLLW. 

Modeled results were verified by contrasting with observations at 123 NOAA’s NOS 

water level stations. The average model-data discrepancy of the four datums was 3.8 cm, 

with a rms difference of 1.6 cm. The errors were interpolated over the whole model grid 

using the TCARI interpolation program. The resulting error fields were incorporated into 

the initial model results to derive the error-corrected tidal datum fields. 

A regular VDatum marine grid was created to conform with the VDatum software tool. 

Tidal datums defined on the unstructured grid were interpolated onto the regular, marine 

grid to form the final datums as input to the VDatum tool. To compromise with the 

limitation of the VDatum software in handling large-size array, the whole marine grid 

was divided into four sections. 

The TSS fields were created separately for each of the four sections of the marine grid. 

They were derived using two methodologies: fitting tidal model results to tidal 

benchmarks leveled in NAVD88 and calculating orthometric-to-tidal datum relationships 

at NOAA tidal gauges. Results from two methods were coupled to create the final TSS 

grids and incorporated into the VDatum tool. 

ACKNOWLEDEGEMENTS 

The authors would also like to express thanks to Rich Patchen, Eugene Wei, Richard 

Schmalz, and Jesse Feyen from CSDL for their valuable suggestions and direct hands-on 

help throughout the whole project effort. 

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(November 2002). 

Parker, B., K. W. Hess, D. Milbert, and S. K. Gill, 2003: A national vertical datum 

transformation tool. Sea Technology, v. 44. no. 9 (Sept. 2003), 10 - 15. 

Spargo, E. A., and J. W. Woolard, 2005. VDatum for the Calcasieu River from Lake 

Charles to the Gulf of Mexico, Louisiana: Tidal Datum Modeling and Population of the 

Grid. NOS Technical Report NOS CS 19, 26 pp. 

Swanson, R. L., 1976: Tides. MESA New York Bight Atlas Monography Series 4. 

Albany, New York. New York Sea Grant Institute. 

Westerink, J. J., R. A. Luettich and J. C. Muccino, 1993: An Advanced ThreeDimensional Circulation Model for Shelves, Coasts, and Estuaries, Report 3: 

Development of a Tidal Constituent Database for the Western North Atlantic and Gulf of 

Mexico, Technical Report DRP-92-6, U.S. ACE Waterways Experiment Station, 

Vicksburg, MS. 

Yang, Z., E. P. Myers, A. Wong, and S. White, (unpublished manuscript): VDatum for 

Chesapeake Bay, Delaware Bay, and Adjacent Coastal Water Areas: Tidal Datum and 

Sea Surface Topography. 
40
41

APPENDIX A. SPECIFICATIONS OF BATHYMETRIC DATA 

Table A.1. Sources and accuracy of bathymetry used for VDatum. 

Source Horizontal 

Resolution 

Reported 

Horizontal 

Accuracy 

Vertical 

Resolution 

Reported 

Vertical 

Accuracy 

Horizon

tal 

Datum 

Vertical 

Datum 

Soundings from 

USACE surveys of 

channels, rivers, 

canals, and 

dredged areas 

1:1200 to 

1:48,000 

usually 

2 – 5 m 1 coarser 

than 1 m 1

0.25 – 1.0 ft 

at depths less 

than 15 ft 

1.0 – 2.0 ft 

at depths greater 

than 15 ft 1 

NAD 83 

by survey 

MLLW 

MLW, 

MLG, 

MLT 

Soundings from 

the NOAA NOS 

Hydrographic 

Survey Data Base 

1:5000 to 

1:80,000 2

IHO and U.S. 

standards 3

variable by 

survey 

IHO and U.S. 

standards 3

transfor

med to 

NAD 83 

by survey 

MLLW, 

MLW, 

usually 

Soundings digitized 

from NOAA 

Navigational Charts 

or ENC 

subsampled 

from survey 

source 

less accurate 

than 

survey source 

~0.1 m 

reported 

less accurate 

than 

survey source 

NAD 83 

WGS 84 

MLLW 

on charts 

after 1980 4

1

 Table 3-1, U.S. Army Corps of Engineers Hydrographic Survey Manual, 2002. 2

 1 cm spacing between sounding lines and 5-6 mm sounding density along lines at the scale of the survey. 

 Soundings are twice as dense along lines than across lines. 3

 See Table 3.2 below. 

4

 Original MLW and other tidal datums are designated as MLLW on NOAA navigational charts. 5

 Depth values that were used to generate the CRM were non-uniformly georeferenced. 

6 Smith, W.H.F. and D.T. Sandwell, 1997, Global Sea Floor Topography from Satellite Altimetry and Ship Depth 

 Soundings, Science 277 (5334), p.1956-1962. 
42

Table A.2. Minimum Accuracy Standards for Depth Measurements of NOAA 

Surveys. 

Survey Year* Horizontal 

Accuracy 

Vertical 

Accuracy Standard 

1998 – present 

Order 1 

1 – 100 m depth: 

5.0 m + 5% of depth 

 

Order 2 

100 – 200 m depth: 

20 m + 5% of depth 

Order 3 

100 – 200 m depth: 

150 m + 5% of depth 

Order 1 

 1 – 100 m depth: 

0.5 – 1.4 m 

Order 2 

100 – 200 m depth: 

2.5 – 4.7 m 

 

Order 3 

> 100 m depth: 

same as Order 2 

IHO S-44 1

 

and NOAA 2 

1988 – 1998 

95% probability that the 

true position lies within a 

circle of radius 1.5 mm, at 

the scale of the survey 

0 – 30 m depth: 0.3 m 

> 30 m depth: 1% of depth 

IHO S-44 1

 

and NOAA 2 

1982 – 1988 

probable error shall seldom 

exceed twice the plottable 

error (1.0 mm) at the scale 

of the survey 

0 – 20 m depth: 0.3 m 

20 – 100 m depth: 1.0 m 

> 100 m depth: 1% of depth 

IHO S-44 1

 

and NOAA 2 

1957 – 1982 

maximum error of plotted 

positions shall seldom 

exceed 1.5 mm at the scale 

of the survey 

0 – 20 m depth: 0.3 m 

20 – 100 m depth: 1.0 m 

> 100 m depth: 1% of depth 

IHC 3 

NOAA 2

and 

IHO S-44 1

before 1957 undetermined undetermined undocumented 

* end of field collection 1

 International Hydrographic Organization (IHO) Standards for Hydrographic Surveys, Special Publication 44, 

 (First Edition, 1968; Second Edition, 1982; Third Edition, 1987; Fourth Edition, 1998). 2

 U.S. Department of Commerce Coast and Geodetic Survey Hydrographic Manual (1931, 1942, 1960, 1976) 

 NOAA NOS Office of Coast Survey Specifications and Deliverables, 1999 – 2006. 

 NOAA was established in 1970. 

3

 International Hydrographic Conference, 1957. 
43

APPENDIX B. WATER LEVEL STATION DATA 

Table B.1. Tidal and orthometric datums (meters) relative to mean sea level for NOS 

water level stations in Long Island Sound, New York Harbor, and Narragansett Bay 

area. The ‘N/A’s in the table denote missing values. 

No. Station 

ID # 

Latitude 

(oN) 

Longitude 

(oW) 

MHHW 

(m) 

MHW 

(m) 

MLW 

(m) 

MLLW 

(m) 

NAVD88 

 (m) 

Epoch Year 

1 8447281 41.74 -71.1317 0.814 0.738 -0.634 -0.69 N/A 1983-2001 

2 8447386 41.705 -71.1633 0.785 0.711 -0.618 -0.671 N/A 1983-2001 

3 8447387 41.705 -71.1733 0.807 0.71 -0.625 -0.677 N/A 1960-1978 

4 8450768 41.465 -71.1933 0.593 0.514 -0.453 -0.489 0.106 1983-2001 

5 8450898 41.6517 -71.21 0.755 0.677 -0.593 -0.639 N/A 1983-2001 

6 8450948 41.6383 -71.2117 0.699 0.617 -0.527 -0.581 N/A 1983-2001 

7 8451301 41.5583 -71.2367 0.645 0.557 -0.479 -0.523 N/A 1983-2001 

8 8451351 41.4867 -71.2383 0.589 0.518 -0.434 -0.474 N/A 1983-2001 

9 8451552 41.6367 -71.255 0.752 0.676 -0.566 -0.616 N/A 1983-2001 

10 8451929 41.6683 -71.28 0.719 0.634 -0.634 -0.683 N/A 1960-1978 

11 8452154 41.6967 -71.2933 0.722 0.646 -0.646 -0.698 N/A 1960-1978 

12 8452555 41.58 -71.3217 0.69 0.617 -0.522 -0.569 N/A 1960-1978 

13 8452660 41.505 -71.3267 0.645 0.57 -0.487 -0.529 0.093 1983-2001 

14 8452944 41.7167 -71.3433 0.756 0.68 -0.59 -0.639 N/A N/A 

15 8453033 41.7517 -71.3683 0.759 0.684 -0.61 -0.663 N/A 1983-2001 

16 8453201 41.4633 -71.3617 0.611 0.537 -0.453 -0.497 N/A 1983-2001 

17 8453465 41.5733 -71.3717 0.661 0.576 -0.573 -0.619 N/A 1960-1978 

18 8453572 41.6667 -71.3783 0.72 0.64 -0.556 -0.602 N/A 1960-1978 

19 8453733 41.7667 -71.3867 0.755 0.676 -0.677 -0.735 N/A 1960-1978 

20 8453742 41.4967 -71.3867 0.639 0.567 -0.485 -0.529 N/A 1983-2001 

21 8453999 41.4517 -71.4017 0.552 0.472 -0.546 -0.603 N/A 1983-2001 

22 8454000 41.8067 -71.4017 0.79 0.715 -0.631 -0.686 0.068 1983-2001 

23 8454049 41.585 -71.4083 0.683 0.609 -0.52 -0.567 N/A 1983-2001 

24 8454341 41.46 -71.4283 0.625 0.548 -0.464 -0.502 N/A 1983-2001 

25 8454658 41.4217 -71.455 0.576 0.497 -0.493 -0.533 N/A 1960-1978 

26 8455083 41.3633 -71.49 0.562 0.485 -0.43 -0.468 N/A 1983-2001 

27 8458022 41.3233 -71.7533 0.458 0.392 -0.378 -0.418 0.114 1983-2001 

28 8458694 41.305 -71.86 0.457 0.374 -0.412 -0.457 0.096 1983-2001 

29 8459338 41.1733 -71.5567 0.535 0.459 -0.411 -0.446 N/A 1983-2001 

30 8459681 41.1583 -71.6133 0.482 0.408 -0.383 -0.418 N/A 1983-2001 

31 8460469 41.335 -71.9117 0.521 0.427 -0.396 -0.46 N/A N/A 

32 8461392 41.5233 -72.0783 0.524 0.426 -0.497 -0.568 0.035 1983-2001 

33 8461467 41.43 -72.0933 0.488 0.395 -0.438 -0.502 N/A 1983-2001 

34 8461490 41.355 -72.0867 0.462 0.372 -0.409 -0.468 0.092 1983-2001 

35 8461491 41.36 -72.0917 0.467 0.375 -0.411 -0.472 N/A 1960-1978 

36 8461925 41.325 -72.1867 0.472 0.386 -0.398 -0.446 N/A 1983-2001 

37 8462764 41.32 -72.3517 0.59 0.506 -0.503 -0.557 N/A 1983-2001 

38 8463348 41.4517 -72.465 0.488 0.413 -0.412 -0.443 N/A 1983-2001 

39 8463701 41.2683 -72.5317 0.801 0.709 -0.679 -0.751 0.103 1983-2001 

40 8464041 41.27 -72.59 0.847 0.753 -0.756 -0.826 N/A 1960-1978 

41 8464445 41.2717 -72.6667 0.887 0.792 -0.79 -0.86 N/A 1983-2001 

42 8465233 41.2617 -72.8183 0.992 0.896 -0.886 -0.956 0.086 1983-2001 

43 8465692 41.2517 -72.905 1.035 0.934 -0.93 -1.001 N/A 1983-2001 

44 8465705 41.2833 -72.9083 1.034 0.936 -0.939 -1.013 N/A 1983-2001 

45 8465748 41.2933 -72.9167 1.046 0.945 -0.948 -1.021 0.076 1983-2001 
44

46 8466375 41.205 -73.0417 1.058 0.96 -0.957 -1.034 0.074 1983-2001 

47 8466442 41.2183 -73.055 1.062 0.962 -0.964 -1.039 0.071 1983-2001 

48 8466664 41.275 -73.0883 1.202 1.1 -0.987 -1.062 0.02 1983-2001 

49 8466791 41.1867 -73.1133 1.091 0.991 -0.97 -1.043 0.185 1983-2001 

50 8466797 41.2033 -73.1117 1.115 1.013 -0.993 -1.067 0.054 1983-2001 

51 8467150 41.1733 -73.1817 1.127 1.025 -1.03 -1.104 0.067 1983-2001 

52 8467373 41.1567 -73.2133 1.13 1.027 -1.031 -1.107 N/A 1983-2001 

53 8467726 41.1333 -73.2833 1.143 1.041 -1.043 -1.117 0.051 1983-2001 

54 8468448 41.0967 -73.415 1.174 1.07 -1.084 -1.163 0.05 1983-2001 

55 8468609 41.065 -73.445 1.181 1.076 -1.086 -1.164 N/A 1983-2001 

56 8468799 41.0383 -73.48 1.2 1.092 -1.091 -1.162 N/A 1983-2001 

57 8469549 41.0167 -73.5967 1.214 1.095 -1.094 -1.173 N/A 1960-1978 

58 8510321 41.07 -71.8583 0.442 0.365 -0.397 -0.427 N/A 1960-1978 

59 8510448 41.0733 -71.935 0.393 0.306 -0.305 -0.357 N/A 1983-2001 

60 8510560 41.0483 -71.96 0.393 0.306 -0.325 -0.377 0.02 1983-2001 

61 8510719 41.2567 -72.03 0.427 0.338 -0.373 -0.434 N/A 1983-2001 

62 8511171 41.035 -72.19 0.469 0.378 -0.378 -0.439 N/A 1960-1978 

63 8511236 41.1717 -72.205 0.491 0.396 -0.396 -0.457 N/A 1960-1978 

64 8512354 40.8367 -72.48 0.559 0.475 -0.535 -0.58 N/A 1983-2001 

65 8512668 41.015 -72.5617 0.876 0.784 -0.77 -0.836 N/A 1983-2001 

66 8512735 40.935 -72.5817 0.501 0.411 -0.438 -0.492 N/A 1983-2001 

67 8512987 40.9817 -72.645 0.914 0.82 -0.812 -0.878 N/A 1983-2001 

68 8514422 40.965 -73.0433 1.086 0.988 -0.976 -1.045 N/A 1983-2001 

69 8514560 40.95 -73.0767 1.108 1.01 -1.005 -1.073 0.059 1983-2001 

70 8515586 40.9 -73.3533 1.212 1.105 -1.111 -1.18 N/A 1983-2001 

71 8515921 40.91 -73.4317 1.175 1.066 -1.078 -1.143 N/A 1983-2001 

72 8516061 40.8733 -73.47 1.22 1.109 -1.114 -1.182 N/A 1983-2001 

73 8516274 40.885 -73.5317 1.24 1.127 -1.098 -1.18 N/A N/A 

74 8516287 40.8833 -73.545 1.24 1.127 -1.098 -1.18 N/A N/A 

75 8516299 40.9033 -73.55 1.242 1.132 -1.122 -1.2 N/A 1983-2001 

76 8516614 40.8633 -73.655 1.217 1.106 -1.11 -1.181 0.084 1983-2001 

77 8516761 40.8317 -73.7033 1.212 1.103 -1.121 -1.203 N/A 1983-2001 

78 8516945 40.81 -73.765 1.191 1.081 -1.1 -1.185 N/A 1983-2001 

79 8516990 40.7933 -73.7817 1.191 1.08 -1.098 -1.182 0.058 1983-2001 

80 8517125 40.7983 -73.8133 1.195 1.086 -1.082 -1.173 N/A 1960-1978 

81 8517276 40.7833 -73.8567 1.14 1.03 -1.034 -1.119 N/A 1960-1978 

82 8517667 40.7617 -73.9467 0.804 0.701 -0.671 -0.738 N/A N/A 

83 8517732 40.7067 -73.9733 0.756 0.653 -0.652 -0.722 N/A 1960-1978 

84 8517811 40.59 -73.9983 0.826 0.723 -0.722 -0.792 N/A 1960-1978 

85 8517921 40.665 -74.0133 0.823 0.72 -0.722 -0.786 N/A 1960-1978 

86 8518051 41 -73.66 1.219 1.097 -1.098 -1.189 N/A N/A 

87 8518091 40.9617 -73.6717 1.222 1.112 -1.11 -1.183 N/A 1960-1978 

88 8518490 40.8917 -73.7817 1.216 1.107 -1.115 -1.194 0.084 1983-2001 

89 8518621 40.8 -73.8733 1.164 1.055 -1.055 -1.143 N/A 1960-1978 

90 8518639 40.8017 -73.9067 1.059 0.952 -0.949 -1.03 0.043 1983-2001 

91 8518643 40.8 -73.9283 0.805 0.704 -0.704 -0.777 N/A 1960-1978 

92 8518668 40.7767 -73.9417 0.808 0.713 -0.714 -0.772 N/A 1960-1978 

93 8518687 40.7583 -73.9583 0.751 0.65 -0.669 -0.733 0.061 1983-2001 

94 8518695 40.7467 -73.9683 0.758 0.655 -0.659 -0.732 N/A 1960-1978 

95 8518699 40.7117 -73.9683 0.719 0.62 -0.667 -0.727 0.066 1983-2001 

96 8518750 40.7 -74.015 0.758 0.66 -0.72 -0.783 0.064 1983-2001 

97 8518903 40.8783 -73.925 0.68 0.588 -0.585 -0.643 N/A 1960-1978 
45

98 8518905 40.9033 -73.9167 0.68 0.588 -0.588 -0.649 N/A 1960-1978 

99 8518924 41.2183 -73.9633 0.57 0.485 -0.498 -0.55 N/A 1960-1978 

100 8519024 40.6067 -74.055 0.795 0.692 -0.695 -0.759 N/A 1960-1978 

101 8519200 40.645 -74.18 0.85 0.747 -0.808 -0.878 N/A 1960-1978 

102 8519436 40.5433 -74.14 0.805 0.702 -0.731 -0.792 N/A N/A 

103 8519483 40.64 -74.1467 0.834 0.736 -0.782 -0.846 0.054 1983-2001 

104 8519789 40.5567 -74.2233 0.899 0.795 -0.796 -0.881 N/A 1960-1978 

105 8530095 40.945 -73.9183 0.62 0.543 -0.6 -0.658 -0.022 1983-2001 

106 8530505 40.8133 -73.9783 0.732 0.646 -0.646 -0.71 N/A 1960-1978 

107 8530645 40.7667 -74.0183 0.759 0.667 -0.665 -0.735 N/A 1960-1978 

108 8530696 40.7517 -74.0967 0.841 0.752 -0.855 -0.926 N/A 1983-2001 

109 8530743 40.7317 -74.1167 0.866 0.771 -0.816 -0.884 N/A 1983-2001 

110 8530772 40.7283 -74.1033 0.862 0.762 -0.827 -0.901 0.039 1983-2001 

111 8530802 40.7167 -74.0317 0.762 0.67 -0.671 -0.732 N/A N/A 

112 8530882 40.6733 -74.14 0.848 0.744 -0.794 -0.856 N/A 1983-2001 

113 8530986 40.655 -74.085 0.793 0.692 -0.719 -0.789 N/A 1960-1978 

114 8531232 40.4917 -74.2817 0.859 0.755 -0.796 -0.863 N/A 1960-1978 

115 8531262 40.5083 -74.3117 0.879 0.777 -0.812 -0.87 N/A 1983-2001 

116 8531390 40.4783 -74.3567 0.898 0.798 -0.858 -0.929 N/A 1960-1978 

117 8531545 40.44 -74.1983 0.842 0.741 -0.798 -0.863 0.031 1983-2001 

118 8531592 40.4483 -74.1433 0.805 0.704 -0.704 -0.753 N/A 1960-1978 

119 8531662 40.4183 -74.035 0.808 0.705 -0.731 -0.792 N/A 1960-1978 

120 8531680 40.4667 -74.01 0.807 0.707 -0.727 -0.785 0.073 1983-2001 

121 8531991 40.3033 -73.9767 0.76 0.655 -0.686 -0.744 0.075 1983-2001 

122 8532337 40.185 -74.0083 0.765 0.658 -0.692 -0.744 N/A 1960-1978 

123 8532591 40.1017 -74.035 0.706 0.605 -0.621 -0.676 0.063 1983-2001 
46

Table B.2. NOS Water Level Station Names 

No. Station ID # Station Name 

1 8447281 STEEPBROOK 

2 8447386 FALL RIVER HOPE BAY 

3 8447387 BORDEN FLATS LIGHT MT 

4 8450768 SAKONNET 

5 8450898 BAY OIL CORPORATION 

6 8450948 ANTHONY POINT 

7 8451301 THE GLEN SAKONNET RIVER 

8 8451351 SACHUEST 

9 8451552 BRISTOL FERRY 

10 8451929 BRISTOL BRISTOL HARBOR RI 

11 8452154 BRISTOL HIGHLANDS RI 

12 8452555 NAVY PIER PRUDENCE ISLAN 

13 8452660 NEWPORT NARRAGANSETT BAY 

14 8452944 CONIMICUT LIGHT NARRAGAN 

15 8453033 BAY SPRING BULLOCK COVE R 

16 8453201 CASTLE HILL 

17 8453465 CONANICUT POINT RI 

18 8453572 WARWICK POINT 

19 8453733 RHODE IS YACHT CLUB RI 

20 8453742 WEST JAMESTOWN 

21 8453999 BEAVERTAIL POINT 

22 8454000 PROVIDENCE PROVIDENCE RIV 

23 8454049 QUONSET POINT 

24 8454341 BOSTON NECK 

25 8454658 NARRAGANSETT PIER RI 

26 8455083 POINT JUDITH HARBOR OF R 

27 8458022 WEEKAPAUG POINT BLOCK ISL 

28 8458694 WATCH HILL POINT 

29 8459338 BLOCK ISLAND HARBOR OLD 

30 8459681 BLOCK ISLAND SW END BLOCK 

31 8460469 STONINGTON STONINGTON HBR 

32 8461392 NORWICH THAMES RIVER CT 

33 8461467 YALE BOATHOUSE THAMES RI 

34 8461490 NEW LONDON THAMES RIVER C 

35 8461491 NEW LONDON (BACKUP) CT 

36 8461925 NIANTIC NIANTIC RIVER CT 

37 8462764 LYME HWY BR CT RIVER CT 

38 8463348 TYLERVILLE CONNECTICUT R 

39 8463701 CLINTON CLINTON HARBOR 

40 8464041 MADISON BEACH CLUB LONG I 

41 8464445 GUILFORD GUILFORD HARBOR 

42 8465233 BRANFORD BRANFORD RIVER C 

43 8465692 LIGHTHOUSE POINT NEW HAV 
47

44 8465705 NEW HAVEN NEW HAVEN HARB 

45 8465748 NEW HAVEN 

46 8466375 GULF BEACH 

47 8466442 MILFORD HARBOR CT 

48 8466664 MURPHY'S BOAT YARD HOUSAT 

49 8466791 SNIFFENS POINT HOUSATONIC 

50 8466797 I-95 BRIDGE HOUSATONIC RI 

51 8467150 BRIDGEPORT BRIDGEPORT HAR 

52 8467373 BLACK ROCK HARBOR CEDAR 

53 8467726 SOUTHPORT SOUTHPORT HARB 

54 8468448 SOUTH NORWALK NORWALK RI 

55 8468609 ROWAYTON FIVEMILE RIVER C 

56 8468799 LONG NECK PT LONG ISLAND 

57 8469549 COSCOB HARBOR CT 

58 8510321 MONTAUK POINT LIGHT NY 

59 8510448 U S COAST GUARD STATION L 

60 8510560 MONTAUK FORT POND BAY 

61 8510719 SILVER EEL POND FISHERS 

62 8511171 THREEMILE HARBOR ENTRANCE 

63 8511236 PLUM ISLAND PLUM GUT HARB 

64 8512354 SHINNECOCK INLET 

65 8512668 MATTITUCK INLET LONG ISL 

66 8512735 SOUTH JAMESPORT GREAT PE 

67 8512987 NORTHVILLE FUEL DOCK LONG 

68 8514422 CEDAR BEACH NY 

69 8514560 PORT JEFFERSON NY 

70 8515586 NORTHPORT NORTHPORT BAY N 

71 8515921 LLOYD HARBOR LIGHTHOUSE 

72 8516061 COLD SPRINGS HARBOR NY 

73 8516274 FRIEDMAN PIER SITE #4 NY 

74 8516287 GILMORE PIER SITE #4 NY 

75 8516299 BAYVILLE BRIDGE OYSTER B 

76 8516614 GLEN COVE YACHT CLUB LON 

77 8516761 PORT WASHINGTON MANHASSS 

78 8516945 KINGS POINT LONG ISLAND 

79 8516990 WILLETS POINT LITTLE BAY 

80 8517125 WHITESTONE NY 

81 8517276 COLLEGE PT FT OF 110TH ST 

82 8517667 CON EDISON DOCK 37TH AVE 

83 8517732 WALLABOUT BAY BKLN NAVY Y 

84 8517811 GRAVESEND BAY NORTON PT B 

85 8517921 GOWANUS BAY NY 

86 8518051 PORT CHESTER NY 

87 8518091 RYE BEACH AMUSEMENT PARK 

88 8518490 NEW ROCHELLE NY 

89 8518621 HUNTS PT NY 

90 8518639 PORT MORRIS EAST 138TH S 
48

91 8518643 RANDALLS IS NY 

92 8518668 HORNS HOOK E. 90TH STREE 

93 8518687 QUEENSBORO BRIDGE EAST RI 

94 8518695 EAST 41ST STREET PIER NY 

95 8518699 WILLIAMSBURG BRIDGE 

96 8518750 THE BATTERY NEW YORK HAR 

97 8518903 SPUYTEN DUYVIL CK ENT HUD 

98 8518905 RIVERDALE HUDSON RIVER NY 

99 8518924 HAVERSTRAW BAY 

100 8519024 FORT WADSWORTH STATEN ISL 

101 8519200 PORT IVORY ARTHUR KILL NY 

102 8519436 GREAT KILLS HARBOR NY 

103 8519483 BERGEN POINT WEST REACH K 

104 8519789 ROSSVILLE STATEN ISLAND N 

105 8530095 ALPINE HUDSON RIVER 

106 8530505 EDGEWATER HUDSON RIVER NJ 

107 8530645 UNION CITY HUDSON RIVER N 

108 8530696 BELLEVILLE TPKE HACKENSA 

109 8530743 POINT NO POINT PASSAIC R 

110 8530772 KEARNY POINT HACKENSACK R 

111 8530802 JERSEY CITY PA-RR FERRY N 

112 8530882 PORT ELIZABETH NEWARK BA 

113 8530986 CONSTABLE HOOK UPPER BAY 

114 8531232 SOUTH AMBOY RARITAN RIVER 

115 8531262 KEASBEY RARITAN RIVER 

116 8531390 SAYREVILLE RARITAN RIVER 

117 8531545 KEYPORT RARITAN BAY 

118 8531592 WAACKAACK CK RARITAN BAY 

119 8531662 ATLANTIC HIGHLANDS SANDY 

120 8531680 SANDY HOOK 

121 8531991 LONG BRANCH FISHING PIER 

122 8532337 BELMAR OUTSIDE NJ 

123 8532591 MANASQUAN INLET NJ 
49

Table B.3. Comparisons of tidal range at stations updated from the 1960-1978 

National Tidal Datum Epoch (NTDE) to the 1983-2001 NTDE. 

No. Station ID Range (m) 

1960-1978 

Range (m) 

1983-2001 Ratio (%) Difference (m) 

Percentage 

(%) 

1 8447281 1.542 1.504 0.975 -0.038 2.514 

2 8447386 1.494 1.456 0.975 -0.038 2.544 

3 8450768 1.106 1.082 0.978 -0.024 2.232 

4 8450898 1.42 1.394 0.981 -0.026 1.874 

5 8450948 1.311 1.28 0.977 -0.031 2.365 

6 8451301 1.189 1.168 0.983 -0.021 1.758 

7 8451351 1.082 1.063 0.982 -0.019 1.775 

8 8451552 1.402 1.368 0.976 -0.034 2.461 

9 8452660 1.195 1.174 0.983 -0.021 1.757 

10 8453033 1.453 1.422 0.979 -0.031 2.157 

11 8453201 1.125 1.108 0.985 -0.017 1.497 

12 8453742 1.189 1.168 0.983 -0.021 1.758 

13 8453999 1.173 1.155 0.984 -0.018 1.587 

14 8454000 1.512 1.476 0.976 -0.036 2.397 

15 8454049 1.275 1.25 0.98 -0.025 1.98 

16 8454341 1.146 1.127 0.983 -0.019 1.676 

17 8455083 1.049 1.03 0.982 -0.019 1.781 

18 8458022 0.892 0.876 0.982 -0.016 1.81 

19 8458694 0.92 0.914 0.993 -0.006 0.708 

20 8459338 1 0.981 0.981 -0.019 1.893 

21 8459681 0.916 0.9 0.983 -0.016 1.762 

22 8461392 1.1 1.092 0.992 -0.008 0.76 

23 8461467 1 0.99 0.99 -0.01 0.979 

24 8461490 0.939 0.93 0.991 -0.009 0.94 

25 8461925 0.933 0.918 0.984 -0.015 1.621 

26 8462764 1.155 1.147 0.993 -0.008 0.712 

27 8463348 0.939 0.931 0.992 -0.008 0.833 

28 8464445 1.743 1.747 1.002 0.004 0.229 

29 8465233 1.951 1.948 0.999 -0.003 0.14 

30 8465692 2.039 2.036 0.998 -0.003 0.153 

31 8465705 2.049 2.047 0.999 -0.002 0.098 

32 8465748 2.067 2.067 1 0 0.022 

33 8466375 2.094 2.092 0.999 -0.002 0.094 

34 8466442 2.103 2.101 0.999 -0.002 0.101 

35 8466664 2.268 2.264 0.998 -0.004 0.177 

36 8466791 2.136 2.134 0.999 -0.002 0.094 

37 8466797 2.184 2.182 0.999 -0.002 0.092 

38 8467150 2.234 2.231 0.999 -0.003 0.143 

39 8468609 2.35 2.345 0.998 -0.005 0.213 

40 8468799 2.356 2.362 1.003 0.006 0.25 

41 8510448 0.771 0.75 0.973 -0.021 2.761 

42 8510560 0.789 0.77 0.975 -0.019 2.492 

43 8510719 0.863 0.861 0.998 -0.002 0.184 
50

44 8512354 1.152 1.139 0.989 -0.013 1.147 

45 8512735 1.027 0.993 0.967 -0.034 3.383 

46 8512987 1.814 1.792 0.988 -0.022 1.196 

47 8514422 2.137 2.131 0.997 -0.006 0.265 

48 8514560 2.185 2.181 0.998 -0.004 0.202 

49 8515586 2.39 2.392 1.001 0.002 0.099 

50 8515921 2.316 2.318 1.001 0.002 0.066 

51 8516061 2.396 2.402 1.003 0.006 0.261 

52 8516299 2.435 2.442 1.003 0.007 0.273 

53 8516614 2.393 2.398 1.002 0.005 0.222 

54 8516761 2.411 2.415 1.002 0.004 0.167 

55 8516945 2.373 2.376 1.001 0.003 0.126 

56 8516990 2.371 2.373 1.001 0.002 0.084 

57 8518490 2.405 2.41 1.002 0.005 0.213 

58 8518639 2.087 2.089 1.001 0.002 0.096 

59 8518687 1.496 1.484 0.992 -0.012 0.805 

60 8518699 1.466 1.446 0.986 -0.02 1.374 

61 8518750 1.561 1.541 0.987 -0.02 1.289 

62 8519483 1.695 1.68 0.991 -0.015 0.889 

63 8530095 1.292 1.278 0.989 -0.014 1.117 

64 8530696 1.783 1.767 0.991 -0.016 0.906 

65 8530743 1.771 1.75 0.988 -0.021 1.187 

66 8530772 1.786 1.763 0.987 -0.023 1.296 

67 8530882 1.719 1.704 0.991 -0.015 0.881 

68 8531262 1.747 1.749 1.001 0.002 0.143 

69 8531545 1.695 1.705 1.006 0.01 0.607 

70 8531680 1.585 1.592 1.004 0.007 0.441 

71 8531991 1.5 1.504 1.003 0.004 0.266 

72 8532591 1.375 1.382 1.005 0.007 0.533 
51

APPENDIX C. TCARI-CORRECTED TIDAL FIELDS ON THE 

UNSTRUCTURED MODEL GRID 

(a) 

MHHW

(b) 

MHW 
52

Figure C.1. Corrected tidal datum fields on the unstructured grid, (a) MHHW, (b) 

MHW, (c) MLW, and (d) MLLW, relative to MSL. Color bars are in meters. 

(c) 

MLW 

(d) 

MLLW
53

APPENDIX D. TIDAL GAUGE AND BENCHMARKS DATA USED TO CREATE 

THE TSS 

Table D.1. Derived NAVD 88-to-LMSL values for each tidal datum at NGS 

benchmarks from the Long Island Sound Tidal Grids. 

Benchmark Latitude Longitude 

From 

MLLW 

(m) 

From 

MLW 

(m) 

From 

MHW 

(m) 

From 

MHHW 

(m) 

Average 

(m) 

Std. 

Dev. 

(m) 

LW0832 41.04722 -71.9583 0.0177 0.0185 0.0149 0.0129 0.0160 0.0026 

LW0831 41.04805 -71.9572 0.0629 0.0636 0.0598 0.0577 0.0610 0.0028 

LW0833 41.05138 -71.9578 0.1038 0.1045 0.0988 0.0967 0.1010 0.0038 

LX0101 41.31777 -72.3503 0.0808 0.0808 0.0658 0.0676 0.0738 0.0082 

LX0102 41.32111 -72.3511 0.0569 0.0565 0.0451 0.0485 0.0518 0.0059 

LX0157 41.35944 -72.0911 0.0938 0.0961 0.0952 0.0977 0.0957 0.0016 

AH9447 41.505 -71.3267 0.089 0.0902 0.098 0.0973 0.0936 0.0047 

AH9448 41.505 -71.3267 0.089 0.0902 0.098 0.0973 0.0936 0.0047 

LW0491 41.50611 -71.3278 0.0862 0.0886 0.1044 0.1041 0.0958 0.0098 

LW0493 41.50666 -71.3272 0.0872 0.0888 0.0994 0.0988 0.0936 0.0064 

LW0489 41.5075 -71.3286 0.0788 0.0814 0.0999 0.0996 0.0899 0.0114 

LX3397 41.52083 -72.0811 0.0392 0.04 0.0386 0.0386 0.0391 0.0007 

LX3226 41.52388 -72.08 0.0326 0.0335 0.0328 0.0328 0.0329 0.0004 

LW5205 41.80638 -71.4011 0.0677 0.0687 0.0662 0.0683 0.0677 0.0011 

LW0150 41.80666 -71.4014 0.0647 0.0657 0.0632 0.0653 0.0647 0.0011 

LW0152 41.80694 -71.4019 0.0645 0.0655 0.0629 0.0651 0.0645 0.0011 

LW0154 41.80722 -71.3992 0.0638 0.0649 0.0621 0.0643 0.0638 0.0012 

AH9453 41.8075 -71.4 0.0641 0.0651 0.0624 0.0646 0.0641 0.0012 

KU1594 40.86277 -73.6544 0.0822 0.0838 0.0838 0.0827 0.0831 0.0008 

KU1595 40.86277 -73.6539 0.0891 0.0907 0.0908 0.0897 0.0901 0.0008 

KU1593 40.86305 -73.6544 0.0853 0.0868 0.0868 0.0858 0.0862 0.0007 

KU0432 40.87555 -73.4692 0.0607 0.0627 0.0596 0.0616 0.0612 0.0013 

KU0373 40.93416 -72.5769 0.1366 0.1369 0.1436 0.1427 0.1400 0.0037 

KU0505 40.94777 -73.075 0.0453 0.0468 0.0462 0.0434 0.0454 0.0015 

KU0506 40.95083 -73.0775 0.0636 0.065 0.0641 0.0612 0.0635 0.0016 

AI1725 41.17333 -73.1817 0.0692 0.0701 0.0707 0.0686 0.0697 0.0009 

LX2344 41.17555 -73.18 0.0663 0.0671 0.0675 0.0654 0.0666 0.0009 

LX0885 41.20472 -73.1117 0.0619 0.0629 0.0642 0.0618 0.0627 0.0011 

LX0470 41.27 -72.5283 0.1058 0.1041 0.106 0.1059 0.1055 0.0009 

AI8467 40.44 -74.1961 0.0434 0.0441 0.0288 0.0309 0.0368 0.0081 

KV0714 40.46111 -74.0042 0.0758 0.0783 0.075 0.0748 0.0760 0.0016 

AB6711 40.4675 -74.01 0.0733 0.0747 0.0723 0.0715 0.0730 0.0014 

KV3521 40.46777 -74.0089 0.0753 0.0765 0.0756 0.0747 0.0755 0.0008 

KV0707 40.46805 -74.0083 0.0755 0.0767 0.0755 0.0747 0.0756 0.0008 

KV0709 40.46805 -74.0086 0.0754 0.0766 0.0755 0.0747 0.0756 0.0008 

KV3519 40.46833 -74.0069 0.0729 0.0741 0.0724 0.0716 0.0728 0.0010 

AB6710 40.46861 -74.0103 0.08 0.0811 0.0744 0.074 0.0774 0.0037 

KV0701 40.47111 -74.0119 0.0857 0.0862 0.0772 0.0767 0.0815 0.0052 

KV2864 40.63777 -74.1464 0.0579 0.0581 0.0567 0.0571 0.0575 0.0007 

KV0442 40.63833 -74.1444 0.0624 0.0627 0.0591 0.0599 0.0610 0.0018 

KV0441 40.63861 -74.1431 0.0577 0.0581 0.0536 0.0545 0.0560 0.0023 

AB6736 40.7 -74.015 0.0706 0.0694 0.063 0.0614 0.0661 0.0046 

AB6737 40.7 -74.015 0.0736 0.0724 0.066 0.0644 0.0691 0.0046 

KV0587 40.70083 -74.0156 0.0681 0.0673 0.0757 0.0727 0.0709 0.0040 
54

KV0579 40.70333 -74.0142 0.0726 0.0718 0.0788 0.0764 0.0749 0.0033 

KV0584 40.70416 -74.0158 0.074 0.0744 0.0814 0.0752 0.0762 0.0035 

KU1418 40.75972 -73.9583 0.0687 0.0688 0.0774 0.0756 0.0726 0.0045 

KU0976 40.79333 -73.7811 0.062 0.0611 0.0621 0.0599 0.0613 0.0010 

KU0978 40.79416 -73.7811 0.0595 0.0587 0.059 0.0567 0.0585 0.0012 

KU0979 40.79416 -73.7814 0.0597 0.0589 0.0591 0.0568 0.0586 0.0013 

KU1012 40.80166 -73.9064 0.0525 0.0518 0.0472 0.0473 0.0497 0.0028 

KU1013 40.80166 -73.9064 0.0435 0.0428 0.0382 0.0383 0.0407 0.0028 

KU1726 40.89055 -73.7822 0.0874 0.0874 0.0899 0.0914 0.0890 0.0020 

KU1724 40.89166 -73.7825 0.088 0.088 0.0895 0.0905 0.0890 0.0012 
55

Table D.2. Location and elevation information for NOAA tide gauges used to create 

the TSS. Tidal datums and NAVD88 are relative to MLLW. Data are from CO-OPS. 

Station numbers marked with an asterisk have NAVD 88 elevations computed from 

NGS. 

BenchMark Latitude 

(deg) 

Longitude 

(deg) 

MLLW 

(m) 

MLW 

(m) 

MSL 

(m) 

MHW 

(m) 

MHHW 

(m) 

NAVD88 

(m) 

8461392 41.52333 -72.07833 0.00 0.07 0.56 0.99 1.09 0.60 

8461490 41.35500 -72.08667 0.00 0.05 0.46 0.84 0.93 0.56 

8462764* 41.32167 -72.35000 0.00 0.05 0.55 1.06 1.14 0.61 

8463348* 41.45167 -72.46500 0.00 0.03 0.44 0.85 0.93 0.38 

8463701 41.26833 -72.53167 0.00 0.07 0.75 1.46 1.55 0.85 

8463827* 41.54167 -72.55167 0.00 0.03 0.40 0.76 0.84 0.29 

8465233 41.26167 -72.81833 0.00 0.07 0.95 1.85 1.94 1.04 

8465748 41.29333 -72.91667 0.00 0.07 1.02 1.96 2.06 1.09 

8466375 41.20500 -73.04167 0.00 0.07 1.03 1.99 2.09 1.10 

8466442 41.21833 -73.05500 0.00 0.07 1.03 2.00 2.10 1.11 

8466573 41.30167 -73.07167 0.00 0.07 1.08 2.20 2.31 1.10 

8466664 41.27500 -73.08833 0.00 0.07 1.06 2.16 2.26 1.08 

8466791 41.18667 -73.11333 0.00 0.07 1.04 2.03 2.13 1.22 

8466797 41.20333 -73.11167 0.00 0.07 1.06 2.08 2.18 1.12 

8467150 41.17333 -73.18167 0.00 0.07 1.10 2.12 2.23 1.17 

8467373* 41.15667 -73.21333 0.00 0.07 1.10 2.13 2.23 1.16 

8467726 41.13333 -73.28333 0.00 0.07 1.11 2.15 2.26 1.16 

8468448 41.09667 -73.41500 0.00 0.07 1.16 2.23 2.33 1.21 

8447930 41.52333 -70.67167 0.00 0.04 0.30 0.58 0.67 0.41 

8447712* 41.59333 -70.90000 0.00 0.04 0.51 1.13 1.20 0.60 

8534720 39.35500 -74.41833 0.00 0.05 0.67 1.27 1.40 0.79 

8532591 40.10167 -74.03500 0.00 0.05 0.67 1.28 1.38 0.73 

8531991 40.30333 -73.97667 0.00 0.05 0.74 1.39 1.50 0.81 

8531680 40.46667 -74.01000 0.00 0.05 0.78 1.49 1.59 0.85 

8531545 40.44000 -74.19833 0.00 0.06 0.86 1.60 1.70 0.89 

8531369* 40.41667 -74.36333 0.00 0.06 0.94 1.76 1.86 0.95 

8531156* 40.54500 -74.26500 0.00 0.05 0.88 1.64 1.73 0.91 

8530772 40.72833 -74.10333 0.00 0.07 0.90 1.66 1.76 0.94 

8530743* 40.73167 -74.11667 0.00 0.06 0.88 1.65 1.75 0.91 

8530591 40.78667 -74.14667 0.00 0.07 0.93 1.78 1.88 0.95 

8530095 40.94500 -73.91833 0.00 0.05 0.65 1.20 1.27 0.63 

8510560 41.04833 -71.96000 0.00 0.05 0.37 0.68 0.77 0.39 

8512735* 40.93500 -72.58167 0.00 0.05 0.49 0.90 0.99 0.63 

8512769* 40.81833 -72.55333 0.00 0.03 0.40 0.80 0.88 0.50 

8513825* 40.73833 -72.86833 0.00 0.03 0.22 0.39 0.44 0.24 

8514560 40.95000 -73.07667 0.00 0.06 1.07 2.08 2.18 1.13 

8515186 40.62667 -73.26000 0.00 0.04 0.34 0.64 0.70 0.40 

8516061* 40.87333 -73.47000 0.00 0.06 1.18 2.29 2.40 1.24 

8516299* 40.90333 -73.55000 0.00 0.07 1.20 2.33 2.44 1.27 

8516614 40.86333 -73.65500 0.00 0.07 1.18 2.28 2.39 1.26 

8516761* 40.83167 -73.70333 0.00 0.08 1.20 2.30 2.41 1.34 

8516990 40.79333 -73.78167 0.00 0.08 1.18 2.26 2.37 1.24 

8517847 40.70333 -73.99500 0.00 0.06 0.78 1.43 1.55 0.89 

8518091 40.96167 -73.67167 0.00 0.07 1.18 2.29 2.40 2.19 

8518490 40.89333 -73.78167 0.00 0.07 1.19 2.30 2.41 1.27 

8518639 40.80167 -73.90667 0.00 0.08 1.03 1.98 2.08 1.07 

8518687 40.75833 -73.95833 0.00 0.06 0.73 1.38 1.48 0.79 
56

8518699 40.71167 -73.96833 0.00 0.06 0.72 1.34 1.44 0.79 

8518750 40.70000 -74.01500 0.00 0.06 0.78 1.44 1.54 0.84 

8519483 40.64000 -74.14667 0.00 0.06 0.84 1.58 1.68 0.90 

8512987 40.98167 -72.64500 0.00 0.06 0.87 1.69 1.79 0.93 

8450768 41.46500 -71.19333 0.00 0.03 0.48 1.00 1.08 0.59 

8450954* 41.61833 -71.20333 0.00 0.04 0.53 1.11 1.20 0.59 

8451552* 41.63667 -71.25500 0.00 0.05 0.61 1.29 1.36 0.70 

8452660 41.50500 -71.32667 0.00 0.04 0.52 1.09 1.17 0.62 

8453742* 41.49667 -71.38667 0.00 0.04 0.52 1.09 1.16 0.61 

8454000 41.80667 -71.40167 0.00 0.05 0.68 1.40 1.47 0.75 

8458022 41.32833 -71.76167 0.00 0.04 0.41 0.81 0.87 0.53 

8458694 41.30500 -71.86000 0.00 0.04 0.45 0.83 0.91 0.55 
57

APPENDIX E. COMPARISON OF DERIVED LIS TSS WITH OBSERVATIONS 

AND ERROR ANALYSIS 

Table E.1. QA/QC Residuals from the Long Island Sound TSS Grid. 

PID Latitude 

(deg) 

Longitude 

(deg) 

MHHW 

Res. 

(m) 

MHW 

Res. 

(m) 

MLW 

Res. 

(m) 

MLLW 

Res. 

(m) 

Avg. 

(m) 

Std. Dev. 

(m) 

LW0832 41.04722 -71.95833 -0.0043 -0.0035 -0.0071 -0.0091 -0.0060 0.0026 

LW0831 41.04805 -71.95722 0.0067 0.0074 0.0036 0.0016 0.0048 0.0027 

LW0833 41.05138 -71.95777 0.0174 0.0181 0.0124 0.0103 0.0146 0.0038 

LX0101 41.31777 -72.35027 0.0107 0.0106 -0.0048 -0.0029 0.0034 0.0084 

LX0102 41.32111 -72.35111 0.0025 0.0021 -0.0093 -0.0059 -0.0027 0.0059 

LX0157 41.35944 -72.09111 -0.0018 0.0006 -0.0003 0.0021 0.0001 0.0016 

AH9447 41.50500 -71.32666 -0.0052 -0.0039 0.0038 0.0032 -0.0005 0.0047 

AH9448 41.50500 -71.32666 -0.0052 -0.0039 0.0038 0.0032 -0.0005 0.0047 

LW0491 41.50611 -71.32777 -0.0090 -0.0067 0.0087 0.0083 0.0003 0.0095 

LW0493 41.50666 -71.32722 -0.0048 -0.0036 0.0048 0.0042 0.0001 0.0051 

LW0489 41.50750 -71.32861 -0.0149 -0.0123 0.0062 0.0059 -0.0038 0.0114 

LX3397 41.52083 -72.08111 0.0001 0.0009 -0.0005 -0.0005 0.0000 0.0007 

LX3226 41.52388 -72.08000 -0.0016 -0.0008 -0.0015 -0.0015 -0.0014 0.0004 

LW5205 41.80638 -71.40111 0.0015 0.0025 0.0000 0.0021 0.0015 0.0011 

LW0150 41.80666 -71.40138 -0.0015 -0.0005 -0.0030 -0.0009 -0.0015 0.0011 

LW0152 41.80694 -71.40194 -0.0016 -0.0005 -0.0031 -0.0010 -0.0016 0.0011 

LW0154 41.80722 -71.39916 -0.0001 0.0009 -0.0019 0.0003 -0.0002 0.0012 

AH9453 41.80750 -71.40000 -0.0006 0.0004 -0.0023 -0.0001 -0.0007 0.0012 

KU1594 40.86277 73.65444 -0.0039 -0.0022 -0.0022 -0.0033 -0.0029 0.0008 

KU1595 40.86277 73.65388 0.0019 0.0036 0.0037 0.0026 0.0029 0.0009 

KU1593 40.86305 73.65444 -0.0007 0.0008 0.0008 -0.0002 0.0002 0.0008 

KU1726 40.89055 73.78222 -0.0023 -0.0022 0.0002 0.0018 -0.0006 0.0020 

KU1724 40.89166 73.78250 -0.0011 -0.0010 0.0010 0.0023 0.0003 0.0016 

KU0432 40.87555 -73.46916 -0.0009 0.0011 -0.0019 0.0000 -0.0004 0.0013 

KU0373 40.93416 -72.57694 -0.0032 -0.0029 0.0038 0.0029 0.0001 0.0037 

KU0505 40.94777 -73.07500 -0.0001 0.0014 0.0008 -0.0020 0.0000 0.0015 

KU0506 40.95083 -73.07750 0.0017 0.0031 0.0022 -0.0007 0.0016 0.0016 

AI1725 41.17333 -73.18166 0.0013 0.0022 0.0028 0.0007 0.0018 0.0009 

LX2344 41.17555 -73.18000 -0.0006 0.0002 0.0006 -0.0015 -0.0003 0.0009 

LX0885 41.20472 -73.11166 -0.0002 0.0008 0.0020 -0.0003 0.0006 0.0011 

LX0470 41.27000 -72.52833 0.0003 -0.0013 0.0006 0.0005 0.0000 0.0009 

AI8467 40.44000 -74.19611 0.0120 0.0127 -0.0027 -0.0006 0.0053 0.0081 

KV0714 40.46111 -74.00416 0.0038 0.0063 0.0031 0.0028 0.0040 0.0016 

AB6711 40.46750 -74.01000 0.0003 0.0018 -0.0006 -0.0014 0.0000 0.0014 

KV3521 40.46777 -74.00888 0.0024 0.0036 0.0027 0.0018 0.0026 0.0007 

KV0707 40.46805 -74.00833 0.0027 0.0039 0.0027 0.0019 0.0028 0.0008 

KV0709 40.46805 -74.00861 0.0026 0.0038 0.0027 0.0019 0.0027 0.0008 

KV3519 40.46833 -74.00694 0.0002 0.0014 -0.0003 -0.0011 0.0000 0.0010 

AB6710 40.46861 -74.01027 0.0073 0.0084 0.0017 0.0013 0.0047 0.0037 

KV0701 40.47111 -74.01194 0.0137 0.0142 0.0052 0.0047 0.0094 0.0052 

KV2864 40.63777 -74.14638 0.0042 0.0045 0.0030 0.0035 0.0038 0.0007 

KV0442 40.63833 -74.14444 0.0088 0.0091 0.0055 0.0062 0.0074 0.0018 

KV0441 40.63861 -74.14305 0.0044 0.0048 0.0002 0.0011 0.0026 0.0023 

AB6736 40.70000 -74.01500 0.0051 0.0040 0.0015 -0.0004 0.0025 0.0025 

AB6737 40.70000 -74.01500 0.0081 0.0070 0.0045 0.0026 0.0055 0.0025 

KV0587 40.70083 -74.01555 0.0046 0.0038 0.0104 0.0076 0.0066 0.0030 
58

KV0579 40.70333 -74.01416 0.0094 0.0089 0.0252 0.0215 0.0163 0.0083 

KV0584 40.70416 -74.01583 0.0117 0.0115 0.0233 0.0184 0.0162 0.0057 

KU1418 40.75972 -73.95833 0.0081 0.0082 0.0168 0.0150 0.0120 0.0045 

KU0976 40.79333 -73.78111 0.0040 0.0031 0.0040 0.0019 0.0033 0.0010 

KU0978 40.79416 -73.78111 0.0008 0.0000 0.0003 -0.0020 -0.0002 0.0012 

KU0979 40.79416 -73.78138 0.0010 0.0002 0.0004 -0.0019 -0.0001 0.0013 

KU1012 40.80166 -73.90638 0.0091 0.0084 0.0039 0.0039 0.0063 0.0028 

KU1013 40.80166 -73.90638 0.0001 -0.0006 -0.0051 -0.0051 -0.0027 0.0028 
59

Table E.2. Long Island Sound TSS Comparison to Tide Gauges and Tidal 

Benchmarks.

PID Latitude (deg) Longitude (deg) NAVD 88 to 

MSL (m) 

TSS Derived 

Value (m) Delta (m) 

8461392 41.52333 -72.07833 0.0350 0.0348 0.0002 

8461490 41.35500 -72.08667 0.0920 0.0923 -0.0003 

8462764 41.32167 -72.35000 0.0620 0.0602 0.0018 

8463348 41.45167 -72.46500 -0.0620 -0.0619 -0.0001 

8463701 41.26833 -72.53167 0.1030 0.1030 0.0000 

8463827 41.54167 -72.55167 -0.1090 -0.1089 -0.0001 

8465233 41.26167 -72.81833 0.0860 0.0863 -0.0003 

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8466791 41.18667 -73.11333 0.1850 0.1825 0.0025 

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8467373 41.15667 -73.21333 0.0560 0.0561 -0.0001 

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8531991 40.30333 -73.97667 0.0750 0.0750 0.0000 

8531680 40.46667 -74.01000 0.0730 0.0729 0.0001 

8531545 40.44000 -74.19833 0.0310 0.0310 0.0000 

8530772 40.72833 -74.10333 0.0390 0.0385 0.0005 

8530743 40.73167 -74.11667 0.0260 0.0262 -0.0002 

8530095 40.94500 -73.91833 -0.0220 -0.0219 -0.0001 

8510560 41.04833 -71.96000 0.0200 0.0226 -0.0026 

8512735 40.93500 -72.58167 0.1380 0.1378 0.0002 

8512769 40.81833 -72.55333 0.0970 0.0967 0.0003 

8514560 40.95000 -73.07667 0.0590 0.0570 0.0020 

8516061 40.87333 -73.47000 0.0580 0.0580 0.0000 

8516299 40.90333 -73.55000 0.0760 0.0770 -0.0010 

8516614 40.86333 -73.65500 0.0840 0.0846 -0.0006 

8516761 40.83167 -73.70333 0.1410 0.1416 -0.0006 

8516990 40.79333 -73.78167 0.0580 0.0582 -0.0002 

8517847 40.70333 -73.99500 0.1100 0.1099 0.0001 

8518091 40.96167 -73.67167 1.0070 0.9973 0.0097 

8518490 40.89333 -73.78167 0.0840 0.0852 -0.0012 

8518639 40.80167 -73.90667 0.0430 0.0432 -0.0002 

8518687 40.75833 -73.95833 0.0610 0.0610 0.0000 

8518699 40.71167 -73.96833 0.0660 0.0662 -0.0002 

8518750 40.70000 -74.01500 0.0640 0.0645 -0.0005 

8519483 40.64000 -74.14667 0.0540 0.0539 0.0001 

8512987 40.98167 -72.64500 0.0580 0.0581 -0.0001 

8450768 41.46500 -71.19333 0.1060 0.1060 0.0000 

8451552 41.63667 -71.25500 0.0910 0.0910 0.0000 

8452660 41.50500 -71.32667 0.0930 0.0942 -0.0012 

8453742 41.49667 -71.38667 0.0860 0.0861 -0.0001 

8454000 41.80667 -71.40167 0.0680 0.0662 0.0018 

8458022 41.32833 -71.76167 0.1140 0.1138 0.0002 
60

8458694 41.30500 -71.86000 0.0960 0.0960 0.0000 

LW0832 41.04722 -71.95833 0.0160 0.0220 -0.0060 

LW0831 41.04805 -71.95722 0.0610 0.0562 0.0048 

LW0833 41.05138 -71.95777 0.1010 0.0864 0.0146 

LX0101 41.31777 -72.35027 0.0738 0.0705 0.0033 

LX0102 41.32111 -72.35111 0.0518 0.0544 -0.0027 

LX0157 41.35944 -72.09111 0.0957 0.0955 0.0002 

AH9447 41.50500 -71.32666 0.0936 0.0942 -0.0006 

AH9448 41.50500 -71.32666 0.0936 0.0942 -0.0006 

LW0491 41.50611 -71.32777 0.0958 0.0955 0.0003 

LW0493 41.50666 -71.32722 0.0936 0.0937 -0.0002 

LW0489 41.50750 -71.32861 0.0899 0.0937 -0.0038 

LX3397 41.52083 -72.08111 0.0391 0.0391 0.0000 

LX3226 41.52388 -72.08000 0.0329 0.0342 -0.0013 

LW5205 41.80638 -71.40111 0.0677 0.0662 0.0015 

LW0150 41.80666 -71.40138 0.0647 0.0662 -0.0015 

LW0152 41.80694 -71.40194 0.0645 0.0661 -0.0016 

LW0154 41.80722 -71.39916 0.0638 0.0640 -0.0002 

AH9453 41.80750 -71.40000 0.0641 0.0647 -0.0006 

KU1594 40.86277 -73.65444 0.0831 0.0860 -0.0029 

KU1595 40.86277 -73.65388 0.0901 0.0871 0.0030 

KU1593 40.86305 -73.65444 0.0862 0.0860 0.0002 

KU0432 40.87555 -73.46916 0.0612 0.0615 -0.0003 

KU0373 40.93416 -72.57694 0.1400 0.1398 0.0001 

KU0505 40.94777 -73.07500 0.0454 0.0454 0.0000 

KU0506 40.95083 -73.07750 0.0635 0.0619 0.0016 

AI1725 41.17333 -73.18166 0.0697 0.0679 0.0018 

LX2344 41.17555 -73.18000 0.0666 0.0669 -0.0003 

LX0885 41.20472 -73.11166 0.0627 0.0622 0.0005 

LX0470 41.27000 -72.52833 0.1055 0.1054 0.0001 

AI8467 40.44000 -74.19611 0.0368 0.0315 0.0053 

KV0714 40.46111 -74.00416 0.0760 0.0720 0.0040 

AB6711 40.46750 -74.01000 0.0730 0.0729 0.0000 

KV3521 40.46777 -74.00888 0.0755 0.0728 0.0027 

KV0707 40.46805 -74.00833 0.0756 0.0728 0.0028 

KV0709 40.46805 -74.00861 0.0756 0.0728 0.0028 

KV3519 40.46833 -74.00694 0.0728 0.0727 0.0000 

AB6710 40.46861 -74.01027 0.0774 0.0727 0.0047 

KV0701 40.47111 -74.01194 0.0815 0.0720 0.0095 

KV2864 40.63777 -74.14638 0.0575 0.0537 0.0038 

KV0442 40.63833 -74.14444 0.0610 0.0536 0.0074 

KV0441 40.63861 -74.14305 0.0560 0.0535 0.0025 

AB6736 40.70000 -74.01500 0.0661 0.0645 0.0016 

AB6737 40.70000 -74.01500 0.0691 0.0645 0.0046 

KV0587 40.70083 -74.01555 0.0710 0.0640 0.0070 

KV0579 40.70333 -74.01416 0.0749 0.0636 0.0113 

KV0584 40.70416 -74.01583 0.0763 0.0623 0.0140 

KU1418 40.75972 -73.95833 0.0726 0.0606 0.0120 

KU0976 40.79333 -73.78111 0.0613 0.0581 0.0032 

KU0978 40.79416 -73.78111 0.0585 0.0587 -0.0002 

KU0979 40.79416 -73.78138 0.0586 0.0587 -0.0001 

KU1012 40.80166 -73.90638 0.0497 0.0434 0.0063 

KU1013 40.80166 -73.90638 0.0407 0.0434 -0.0027 

KU1726 40.89055 -73.78222 0.0890 0.0896 -0.0006 
61

KU1724 40.89166 -73.78250 0.0890 0.0887 0.0003 
62