Seamless Combination of Seamless Combination of Bathymetry and Bathymetry and

Topography:Topography:Transforming Vertical DatumsTransforming Vertical Datums

Dennis Milbert, Ph.D.Dennis Milbert, Ph.D.

Bruce Parker, Ph.D.Bruce Parker, Ph.D.

National Ocean Service, NOAANational Ocean Service, NOAA

AcknowledgementsAcknowledgements Collaboration of USGS and NOAACollaboration of USGS and NOAA

– National Ocean ServiceNational Ocean Service Coast SurveyCoast Survey Coastal Services CenterCoastal Services Center National Geodetic SurveyNational Geodetic Survey

Local Partners (so far)Local Partners (so far)– Florida Marine Research InstituteFlorida Marine Research Institute– Tampa Bay National Estuary ProgramTampa Bay National Estuary Program– Rookery Bay National Estuarine Research ReserveRookery Bay National Estuarine Research Reserve– Port AuthoritiesPort Authorities

Future PartnersFuture Partners– Federal Emergency Management AgencyFederal Emergency Management Agency– U.S. Army Corp of EngineersU.S. Army Corp of Engineers

IntroductionIntroduction

What is a Datum?What is a Datum? When Datums Don’t MatchWhen Datums Don’t Match The Shoreline/Datum ProblemThe Shoreline/Datum Problem Categories of DatumsCategories of Datums VDatum -- the Datum Transformation ToolVDatum -- the Datum Transformation Tool How VDatum WorksHow VDatum Works ExamplesExamples Outcomes and Future WorkOutcomes and Future Work

What is a Datum?What is a Datum?

Two related definitions of “datum”Two related definitions of “datum” IdealizationIdealization

– ““A set of constants defining a coordinate A set of constants defining a coordinate system”system”

RealizationRealization– ““The constants, the coordinate system, and The constants, the coordinate system, and

all points and lines that have been all points and lines that have been consistently determined by measurement consistently determined by measurement and computation”and computation”

Datums Arise From Relative Datums Arise From Relative Measurements, IMeasurements, I

Datum A

10.0

5.0

0.0

5.0

25

20

15

10

5

0

Datums Arise From Relative Datums Arise From Relative Measurements, IIMeasurements, II

Datum B

0.0 0.0

5.0

10.0

15

10

5

0

-5

-10

20

Datums Arise From Relative Datums Arise From Relative Measurements, IIIMeasurements, III

Note: Discontinuity between A & B

Datum A

10.0

5.0

0.0

5.0

25

20

15

10

5

0

Datum B

0.0 0.0

5.0

10.0

15

10

5

0

-5

-10

20

When Datums MatchWhen Datums Match

10.0

5.0

0.0

5.0

25

20

15

10

5

0

(All elevations are now consistent)

10.010.0

15.0

20.0

Datum A

Shoreline/Datum Problem, Shoreline/Datum Problem, II

N N

Mean Lower Low Water(MLLW)

Mean Sea Level(MSL)

15

meters3

MLLWMSL

meters

Shoreline/Datum Problem, Shoreline/Datum Problem, IIII

A shoreline has a vertical datum A shoreline has a vertical datum imbedded in itimbedded in it

If you change a shoreline vertical If you change a shoreline vertical reference --reference --– It will cause translations in the shorelineIt will cause translations in the shoreline– It will also change the shape of the It will also change the shape of the

shorelineshoreline As with all geo-referenced data, only As with all geo-referenced data, only

combine data in a combine data in a common datumcommon datum

Shoreline and Legal IssuesShoreline and Legal Issues

Vertical Datums - 3 Vertical Datums - 3 CategoriesCategories

Tidal DatumsTidal Datums– Related to particular stages of ocean tideRelated to particular stages of ocean tide

Mean Lower Low Water (MLLW)Mean Lower Low Water (MLLW) Mean Sea Level (MSL)Mean Sea Level (MSL)

Orthometric DatumsOrthometric Datums– Related to equipotential surface of the EarthRelated to equipotential surface of the Earth

North American Vertical Datum 1988 (NAVD 88)North American Vertical Datum 1988 (NAVD 88)

Ellipsoidal (3-D) DatumsEllipsoidal (3-D) Datums– Related to an ellipsoidal figure of the EarthRelated to an ellipsoidal figure of the Earth– Heights directly from GPSHeights directly from GPS

North American Datum 1983 (NAD 83)North American Datum 1983 (NAD 83)

Ellipsoidal (3-D) DatumsEllipsoidal (3-D) Datums

WGS 84

NAD 83 Control Point

~2-metershift

Differences in origins cause differences in height above the ellipsoid

NGVD 29 -- 21 US (5 Canada) fixed tide gauges

Orthometric DatumsOrthometric Datums

NAVD 88 -- 1 fixed tide gauge

The adopted control points and constants defining the heights cause NGVD 29 and NAVD 88 to differ by up to 2.2 meters

Tide DatumsTide Datums

Tide datum references are Tide datum references are extracted from tidal measurementsextracted from tidal measurements

Mean Low Water

Mean Lower Low Water

Tides Vary GloballyTides Vary Globally

Tide ranges in feetTide ranges in feet– Cape TownCape Town– DakarDakar– Le HavreLe Havre– SouthamptonSouthampton– BremerhavenBremerhaven

Causes differences Causes differences in the tidal datumsin the tidal datums

Various Tidal/Sounding DatumsVarious Tidal/Sounding Datums

Approximate Lowest Astronomical TideApproximate Lowest Astronomical Tide Approximate Mean Low Water SpringsApproximate Mean Low Water Springs Approximate Mean Low Water TideApproximate Mean Low Water Tide Approximate Mean Low WaterApproximate Mean Low Water Approximate Mean Sea LevelApproximate Mean Sea Level Equinoctial Spring Low WaterEquinoctial Spring Low Water Highest Astronomical TideHighest Astronomical Tide Higher High Water Large TideHigher High Water Large Tide Highest Normal High WaterHighest Normal High Water Higher High WaterHigher High Water Highest High WaterHighest High Water High WaterHigh Water High Water SpringsHigh Water Springs International Great Lakes Datum 1985International Great Lakes Datum 1985 Indian Spring High WaterIndian Spring High Water Indian Spring Low WaterIndian Spring Low Water Lowest Astronomical TideLowest Astronomical Tide Lower Low Water Large TideLower Low Water Large Tide Lowest Low Water SpringsLowest Low Water Springs

Lower Low WaterLower Low Water Lowest Low WaterLowest Low Water Low WaterLow Water Low Water SpringsLow Water Springs Mean Higher High WaterMean Higher High Water Mean Higher WaterMean Higher Water Mean High WaterMean High Water Mean High Water NeapsMean High Water Neaps Mean High Water SpringsMean High Water Springs Mean Lower Low Water SpringsMean Lower Low Water Springs Mean Lower Low WaterMean Lower Low Water Mean Low WaterMean Low Water Mean Low Water NeapsMean Low Water Neaps Mean Low Water SpringsMean Low Water Springs Mean Sea LevelMean Sea Level Mean Tide LevelMean Tide Level Nearly Lowest Low WaterNearly Lowest Low Water Neap TideNeap Tide Spring TideSpring Tide

The Vertical Datum The Vertical Datum ProblemProblem

A sizable number of vertical datumsA sizable number of vertical datums Several versions in each of 3 categoriesSeveral versions in each of 3 categories Topographic data in NAVD 88 or NGVD 29Topographic data in NAVD 88 or NGVD 29 Hydrographic data in MLW and MLLWHydrographic data in MLW and MLLW Newest technology referenced with GPS Newest technology referenced with GPS

(NAD 83, WGS84, or ITRF)(NAD 83, WGS84, or ITRF)

Need a tool to transform between Need a tool to transform between vertical datumsvertical datums

VDatumVDatum

Java application -- Windows-like Java application -- Windows-like graphicsgraphics

Transform heights and soundings Transform heights and soundings between vertical datumsbetween vertical datums

2 modes -- interactive and batch2 modes -- interactive and batch Uses regional datum transformation Uses regional datum transformation

gridsgrids Supports 26 different vertical datumsSupports 26 different vertical datums

VDatum -- Interactive VDatum -- Interactive ModeMode

VDatum -- Batch ModeVDatum -- Batch Mode

VDatum -- Batch Input VDatum -- Batch Input DataData

H07934,27.536908,-82.806664,63.0H07934,27.536908,-82.806664,63.0 H07934,27.537256,-82.813550,66.9H07934,27.537256,-82.813550,66.9 H07934,27.543464,-82.815983,64.9H07934,27.543464,-82.815983,64.9 H07934,27.544878,-82.813717,64.0H07934,27.544878,-82.813717,64.0 H07934,27.547394,-82.812214,64.0H07934,27.547394,-82.812214,64.0 H07934,27.547675,-82.801350,61.0H07934,27.547675,-82.801350,61.0 H07934,27.547728,-82.807472,62.0H07934,27.547728,-82.807472,62.0 H07934,27.533836,-82.822453,69.9H07934,27.533836,-82.822453,69.9 H07934,27.536425,-82.826103,68.9H07934,27.536425,-82.826103,68.9 H07934,27.538631,-82.818847,65.9H07934,27.538631,-82.818847,65.9

VDatum -- Batch Output VDatum -- Batch Output DataData

H07934,27.536908,-82.806664,140.4907H07934,27.536908,-82.806664,140.4907 H07934,27.537256,-82.813550,144.3543H07934,27.537256,-82.813550,144.3543 H07934,27.543464,-82.815983,142.3430H07934,27.543464,-82.815983,142.3430 H07934,27.544878,-82.813717,141.4552H07934,27.544878,-82.813717,141.4552 H07934,27.547394,-82.812214,141.4638H07934,27.547394,-82.812214,141.4638 H07934,27.547675,-82.801350,138.5223H07934,27.547675,-82.801350,138.5223 H07934,27.547728,-82.807472,139.4894H07934,27.547728,-82.807472,139.4894 H07934,27.533836,-82.822453,147.3081H07934,27.533836,-82.822453,147.3081 H07934,27.536425,-82.826103,146.2900H07934,27.536425,-82.826103,146.2900 H07934,27.538631,-82.818847,143.3269H07934,27.538631,-82.818847,143.3269

Vertical Datums in Vertical Datums in VDatumVDatum

TidalTidal– MHHWMHHW– MHWMHW– DTLDTL– MTLMTL– LMSLLMSL– MLWMLW– MLLWMLLW

OrthometricOrthometric– NAVD 88NAVD 88– NGVD 29NGVD 29

EllipsoidalEllipsoidal– NAD 83 (86)NAD 83 (86)– WGS 84 (G873)WGS 84 (G873)– WGS 84 (G730)WGS 84 (G730)– WGS 84 (original)WGS 84 (original)– WGS 72WGS 72– ITRF97ITRF97– ITRF96ITRF96– ITRF94ITRF94– ITRF93ITRF93– and 8 more ...and 8 more ...

The Datum Transformation The Datum Transformation ConstellationConstellation

WGS 84 (G873)

WGS 84 (G730)

WGS 84 (orig.)

ITRF97

ITRF94

ITRF96ITRF93

ITRF92

ITRF91

ITRF90

ITRF89

ITRF88

SIO/MIT 92

NEOS 90

PNEOS 90

NAD 83 (86)

NAVD 88

NGVD 29

LMSL

MHHW

MHW

MTL

DTLMLW

MLLW

How many paths ???

The Datum Transformation The Datum Transformation Roadmap, IRoadmap, I

Each edge is a transformation.

NGVD 29

NAD 83 (86) NAVD 88 LMSL

MHHW

MHW

MTL

DTL

MLW

MLLW

WGS 84 (G873)

WGS 84 (G730)

WGS 84 (orig.)

ITRF97

ITRF94

ITRF96

ITRF93ITRF92ITRF91

ITRF90

ITRF89

ITRF88

SIO/MIT 92

NEOS 90

PNEOS 90

The Datum Transformation The Datum Transformation Roadmap, IIRoadmap, II

NGVD 29

NAD 83 (86) NAVD 88 LMSL

MHHW

MHW

MTL

DTL

MLW

MLLW

WGS 84 (G730)

WGS 84 (orig.)

ITRF97

ITRF94

ITRF96

ITRF93ITRF92ITRF91

ITRF90

ITRF89

ITRF88

SIO/MIT 92

NEOS 90

PNEOS 90

WGS 84 (G873)

NAD 83 (86) -6.9001

WGS 84 (G873) -12.0000 feetNAVD 88 73.1061LMSL 72.5713MLLW 73.6934

Tidal Datum Maps

Figure portraysMSL - MLLW (meters)

Produced by a calibrated and verified hydrodynamic model of Tampa Bay

Digital maps were made for 7 tidal datums

Tidal Benchmark DataTidal Benchmark Data

Geodetic level ties to tidal benchmarks allow evaluation of tide models and calibration of local mean sea level variations.

Integrated Bathy/Topo Integrated Bathy/Topo ModelModel

NOAA BathymetryNOAA Bathymetry

USGS TopographyUSGS Topography

3-D Visualization of Bathy/Topo DEM

(Visualizations are useful, but the form in which the actual data are provided to the coastal marine user is also critical.)

OutcomesOutcomes Transformation tool for integration of diverse Transformation tool for integration of diverse

datasetsdatasets Portable implementationPortable implementation Can be imbedded in GIS software systemsCan be imbedded in GIS software systems Validated against geodetic controlValidated against geodetic control

– Leveled benchmarksLeveled benchmarks– GPS control pointsGPS control points– Tide gaugesTide gauges

Easy to useEasy to use

User can focus on the data, not on the geodesyUser can focus on the data, not on the geodesy

Future Work and More Future Work and More OutcomesOutcomes

Extend to cover entire US coastlineExtend to cover entire US coastline Accuracy maps for the transformationsAccuracy maps for the transformations Support decision process for data acquisitionSupport decision process for data acquisition

– legacy datalegacy data -- perhaps less accurate-- perhaps less accurate– new GPS-based datanew GPS-based data -- through transformation-- through transformation

Intersect various vertical reference planes Intersect various vertical reference planes through a seamless 3-D bathy/topo surfacethrough a seamless 3-D bathy/topo surface

Potential to establish shorelines with new Potential to establish shorelines with new technology and with accuracy equivalent to technology and with accuracy equivalent to that of photogrammetrythat of photogrammetry

Backup SlidesBackup Slides

Tampa BayTampa BayBathy/Topo/ShorelineBathy/Topo/ShorelineDemonstration ProjectDemonstration Project

Mapping the Land-Sea Interface

A Collaborative Approach

Bathy/Topo Digital Elevation Model (DEM)Bathy/Topo Digital Elevation Model (DEM)– NOAA bathymetric data (referenced to the ellipsoid)NOAA bathymetric data (referenced to the ellipsoid)– USGS topographic data (referenced to the ellipsoid)USGS topographic data (referenced to the ellipsoid)– Datum Transformation ToolDatum Transformation Tool (26 ortho, 3-D, and tidal datums) (26 ortho, 3-D, and tidal datums)– geographic distribution of tidal datums from geographic distribution of tidal datums from hydrodynamic modelhydrodynamic model– incorporation of recent hi-res 3rd-party dataincorporation of recent hi-res 3rd-party data (datums, (datums,

standards)standards)– recent hi-res shorelines from recent hi-res shorelines from airborne and satellite remote airborne and satellite remote

sensingsensing– internally consistent shorelinesinternally consistent shorelines (HW, MSL, MLLW) (HW, MSL, MLLW)

from a DEM with a high-resolutionfrom a DEM with a high-resolution shoreline elevation zone shoreline elevation zone– GIS compatibility (with retention of maximum resolution)GIS compatibility (with retention of maximum resolution)– Website-accessible, with tutorials and standardsWebsite-accessible, with tutorials and standards– append other data sets (e.g., demographics, environmental, etc.)append other data sets (e.g., demographics, environmental, etc.)– first steps towards a first steps towards a “National Shoreline”“National Shoreline”

Tampa Bay Tampa Bay

Demonstration ProjectDemonstration Project

Inconsistency between NOAA and USGS shorelinesInconsistency between NOAA and USGS shorelines– referenced to different tidal datumsreferenced to different tidal datums– differences in measurement instruments and proceduresdifferences in measurement instruments and procedures– CONFUSED MARINE USER COMMUNITYCONFUSED MARINE USER COMMUNITY

(for many purposes, consistency is more important than accuracy)(for many purposes, consistency is more important than accuracy)

– (plus, need to minimize the duplication of effort between the two agencies)(plus, need to minimize the duplication of effort between the two agencies)– (plus, need to find the most-cost effective way to map 95,000 miles of coastline in the U.S.)(plus, need to find the most-cost effective way to map 95,000 miles of coastline in the U.S.)

Sparse and outdated bathymetric and topographic dataSparse and outdated bathymetric and topographic data– AND, no national framework to allow the inclusion of recent high-AND, no national framework to allow the inclusion of recent high-

resolution data from other sources (state, county, academic)resolution data from other sources (state, county, academic)

(And thus) a geospatial reference frame for other coastal (And thus) a geospatial reference frame for other coastal data sets that is less consistent and accurate than is data sets that is less consistent and accurate than is neededneeded

Limits our ability to accurately represent the coastal zone Limits our ability to accurately represent the coastal zone and predict impacts on communities and the environmentand predict impacts on communities and the environment– hurricane evacuation planninghurricane evacuation planning ---- local, state, and national boundarieslocal, state, and national boundaries– habitat restorationhabitat restoration ---- electronic navigational chart systemselectronic navigational chart systems– permitting permitting

The problems The problems that motivated this that motivated this

projectproject

Where is the Shoreline?Where is the Shoreline?

NOAA Shoreline

USGS Topo Sheet

Spin 2 satellite imagery

Just 3 of the 26 Datums handled by the Datum Transformation Tool

Allows transformation to a common datum for the blending of different data sets.

Except for around thenavigation channels,the bathymetric datais from the 1950s.

The original topographic data is also primarily fromthe 1950s, with some 1960s and early 1970s data.

Need to be ableto take advantageof other data sources.

In addition to the April 1999 airborne photogrammetry and the SPIN2 satellite data,shoreline data sets will be derived (and inter-compared) from: airborne lidar data, airborne hyperspectral data, IKONOS satellite data, SAR data, and SHOALS (bathymetric lidar) data.

Learning How to Obtain High-Resolution Up-to-Date Shoreline from various Airborne and Satellite Techniques

How to cost-effectively map95,000 miles of U.S. coastline?

The only way to accomplish all this is The only way to accomplish all this is throughthrough

A Collaborative ApproachA Collaborative Approach USGS and NOAA working together to USGS and NOAA working together to

solve complex mapping issues on the solve complex mapping issues on the front endfront end

State and local needs, and participationState and local needs, and participation Working with Federal Emergency Working with Federal Emergency

Management Agency (FEMA) and U.S. Management Agency (FEMA) and U.S. Army Corp of Engineers (USACE)Army Corp of Engineers (USACE)

Local Partners include (so far): Local Partners include (so far): – Florida Marine Research Institute Florida Marine Research Institute – Tampa Bay National Estuary ProgramTampa Bay National Estuary Program– Rookery Bay National Estuarine Research Rookery Bay National Estuarine Research

ReserveReserve– PortsPorts

Combination of Topography and Combination of Topography and Bathymetry Through Application of Bathymetry Through Application of

Calibrated Vertical Datum Calibrated Vertical Datum Transformations in the Tampa Bay Transformations in the Tampa Bay

RegionRegion

Dennis Milbert, Ph.D.Dennis Milbert, Ph.D.

Kurt Hess, Ph.D.Kurt Hess, Ph.D.

National Ocean Service, NOAANational Ocean Service, NOAA

IntroductionIntroduction

What is a Datum?What is a Datum? When Datums Don’t MatchWhen Datums Don’t Match The Shoreline/Datum ProblemThe Shoreline/Datum Problem Categories of DatumsCategories of Datums VDatum -- the Datum Transformation VDatum -- the Datum Transformation

ToolTool Examples in Tampa BayExamples in Tampa Bay Outcomes and Future WorkOutcomes and Future Work