United Kingdom Hydrographic Office Relating Data to a Seamless Vertical Reference Surface Ruth...

United Kingdom Hydrographic OfficeUnited Kingdom Hydrographic Office

Relating Data to a Relating Data to a Seamless Vertical Seamless Vertical Reference SurfaceReference Surface

Relating Data to a Relating Data to a Seamless Vertical Seamless Vertical Reference SurfaceReference Surface

Ruth Adams, UK Hydrographic Office, UKRuth Adams, UK Hydrographic Office, UKRuth Adams, UK Hydrographic Office, UKRuth Adams, UK Hydrographic Office, UK


Why Seamless Data?Why Seamless Data?Why Seamless Data?Why Seamless Data?

Coastal Coastal ZoneZone

ManagemeManagementnt

Coastal Coastal ZoneZone

ManagemeManagementnt

Marine boundaryMarine boundary

delimitationdelimitation

Marine boundaryMarine boundary

delimitationdelimitation

HydrographicHydrographic

surveyingsurveying

HydrographicHydrographic

surveyingsurveying

DefenceDefence

capabilitiescapabilities

DefenceDefence

capabilitiescapabilities

ECDISECDIS

applicationsapplications

ECDISECDIS

applicationsapplications

User choice ofUser choice of

output datumoutput datum

User choice ofUser choice of

output datumoutput datum


Combined Land and Marine Combined Land and Marine DataData

Combined Land and Marine Combined Land and Marine DataData


What is a seamless vertical What is a seamless vertical datum?datum?

What is a seamless vertical What is a seamless vertical datum?datum?

Vertical datum = surface to which Vertical datum = surface to which heights (or depths) of points are heights (or depths) of points are referred.referred.

A seamless vertical datum is one A seamless vertical datum is one which does not vary over time or which does not vary over time or location.location.

Vertical datum = surface to which Vertical datum = surface to which heights (or depths) of points are heights (or depths) of points are referred.referred.

A seamless vertical datum is one A seamless vertical datum is one which does not vary over time or which does not vary over time or location.location.


Current Vertical Datums in use by Current Vertical Datums in use by UK Hydrographic OfficeUK Hydrographic Office

Current Vertical Datums in use by Current Vertical Datums in use by UK Hydrographic OfficeUK Hydrographic Office


Variable Vertical DatumVariable Vertical DatumVariable Vertical DatumVariable Vertical DatumBut Chart Datum is not seamless! It But Chart Datum is not seamless! It

variesvariesspatiallyspatially..

For example the difference between For example the difference between Chart Datum and Ordnance Datum Chart Datum and Ordnance Datum Newlyn is:Newlyn is:

-2.80m at Torquay-2.80m at Torquay-1.50m at Lowestoft-1.50m at Lowestoft-6.10m at Barry-6.10m at Barry+0.60m at Barnstaple+0.60m at Barnstaple

But Chart Datum is not seamless! It But Chart Datum is not seamless! It variesvaries

spatiallyspatially..

For example the difference between For example the difference between Chart Datum and Ordnance Datum Chart Datum and Ordnance Datum Newlyn is:Newlyn is:

-2.80m at Torquay-2.80m at Torquay-1.50m at Lowestoft-1.50m at Lowestoft-6.10m at Barry-6.10m at Barry+0.60m at Barnstaple+0.60m at Barnstaple


A Seamless Surface?A Seamless Surface?A Seamless Surface?A Seamless Surface?

A stable reference surface which could beA stable reference surface which could beconsidered suitable for this isconsidered suitable for this isA stable reference surface which could beA stable reference surface which could beconsidered suitable for this isconsidered suitable for this is

… … Although a regional realisation Although a regional realisation may be more appropriatemay be more appropriate… … Although a regional realisation Although a regional realisation may be more appropriatemay be more appropriate

WGS84 DatumWGS84 DatumWGS84 DatumWGS84 Datum


Vertical DatumsVertical DatumsVertical DatumsVertical Datums

The ultimate aim is to refer all heights The ultimate aim is to refer all heights and depths to WGS84 Datum.and depths to WGS84 Datum.

Currently land applications use MSL or Currently land applications use MSL or a local land datum (for example) for a local land datum (for example) for their heighting whereas marine their heighting whereas marine applications use Chart Datum and applications use Chart Datum and MHWS.MHWS.

It is relatively straight-forward to It is relatively straight-forward to transform land detail to WGS84 Datum transform land detail to WGS84 Datum but data referred to Chart Datum is but data referred to Chart Datum is not easy to convert.not easy to convert.


The ChallengeThe ChallengeThe ChallengeThe Challenge

The challenge is not so much to The challenge is not so much to develop a seamless vertical develop a seamless vertical reference surface, but to develop a reference surface, but to develop a way of relating current and future way of relating current and future datasets to it in a seamless datasets to it in a seamless manner.manner.

The challenge is not so much to The challenge is not so much to develop a seamless vertical develop a seamless vertical reference surface, but to develop a reference surface, but to develop a way of relating current and future way of relating current and future datasets to it in a seamless datasets to it in a seamless manner.manner.


How do you Develop a How do you Develop a Vertical Datum Separation Vertical Datum Separation

Model?Model?

How do you Develop a How do you Develop a Vertical Datum Separation Vertical Datum Separation

Model?Model?

It depends on available information…It depends on available information… For exampleFor example

– What bathymetric and topographic data is What bathymetric and topographic data is held?held?

– Are there ellipsoidal heights at Chart Are there ellipsoidal heights at Chart Datum points?Datum points?

– Is there an accurate geoid model?Is there an accurate geoid model? And it depends on the accuracy And it depends on the accuracy

neededneeded

It depends on available information…It depends on available information… For exampleFor example

– What bathymetric and topographic data is What bathymetric and topographic data is held?held?

– Are there ellipsoidal heights at Chart Are there ellipsoidal heights at Chart Datum points?Datum points?

– Is there an accurate geoid model?Is there an accurate geoid model? And it depends on the accuracy And it depends on the accuracy

neededneeded


UK Example - VORFUK Example - VORFUK Example - VORFUK Example - VORF Connections are known between Chart Connections are known between Chart

Datum and ODN (Ordnance Datum Newlyn) Datum and ODN (Ordnance Datum Newlyn) at tide stations onshore.at tide stations onshore.

Connections are known between Chart Connections are known between Chart Datum and ODN (Ordnance Datum Newlyn) Datum and ODN (Ordnance Datum Newlyn) at tide stations onshore.at tide stations onshore.

Equipotential

ODN

Mean sea level

“True” geoid

ETRF0

CD2

CD1

Local levelling

OSGM02

Equipotential

ODN

Mean sea level

“True” geoid

ETRF0

CD2

CD1

Local levelling

OSGM02

Using a geoid model, can obtain Using a geoid model, can obtain relationship between Chart Datum and relationship between Chart Datum and ETRS89 (a European realisation of WGS84 ETRS89 (a European realisation of WGS84 Datum)Datum)

Using a geoid model, can obtain Using a geoid model, can obtain relationship between Chart Datum and relationship between Chart Datum and ETRS89 (a European realisation of WGS84 ETRS89 (a European realisation of WGS84 Datum)Datum)


Vertical Datum Separation Vertical Datum Separation ModelModel

Vertical Datum Separation Vertical Datum Separation ModelModel

Contours show CD to OS vertical datum (ODN) separation.

Red is 6 metres separation; yellow is 0 metres separation with 0.5 metre interval.


How Good is this Model?How Good is this Model?How Good is this Model?How Good is this Model?

Still relies on co-tidal models – only Still relies on co-tidal models – only guaranteed to be accurate to +/- guaranteed to be accurate to +/- 0.5m in vertical accuracy.0.5m in vertical accuracy.

Does this reflect the current Does this reflect the current minimum sea surface?minimum sea surface?

What does the Mariner need?What does the Mariner need?

Still relies on co-tidal models – only Still relies on co-tidal models – only guaranteed to be accurate to +/- guaranteed to be accurate to +/- 0.5m in vertical accuracy.0.5m in vertical accuracy.

Does this reflect the current Does this reflect the current minimum sea surface?minimum sea surface?

What does the Mariner need?What does the Mariner need?


The Way AheadThe Way AheadThe Way AheadThe Way Ahead

UKHO will develop a new minimum UKHO will develop a new minimum sea surface related to ETRF89.sea surface related to ETRF89.

UKHO will develop a Chart Datum to UKHO will develop a Chart Datum to ETRF89 Datum separation model.ETRF89 Datum separation model.

UKHO will also develop a Chart UKHO will also develop a Chart Datum to minimum sea surface Datum to minimum sea surface corrector surface.corrector surface.

UKHO will develop a new minimum UKHO will develop a new minimum sea surface related to ETRF89.sea surface related to ETRF89.

UKHO will develop a Chart Datum to UKHO will develop a Chart Datum to ETRF89 Datum separation model.ETRF89 Datum separation model.

UKHO will also develop a Chart UKHO will also develop a Chart Datum to minimum sea surface Datum to minimum sea surface corrector surface.corrector surface.


Complex Datum Surfaces Complex Datum Surfaces Around the CoastAround the Coast

Complex Datum Surfaces Complex Datum Surfaces Around the CoastAround the Coast

MinimumRef. Surface

Coastline

ODN

CD

GeoidCorrector Surface between CD and Minimum Sea Surface

VO

RF

Mo

del

ICZM Model OSGM 02 ( Corrector Surface )

CD-ODN diff from ATT

ETRF89

OSGM 02

Min. Sea Surface


The UKHO ModelThe UKHO ModelThe UKHO ModelThe UKHO Model

This could be done using modern satellite This could be done using modern satellite data – expected accuracy +/- 0.2m 1 sigma.data – expected accuracy +/- 0.2m 1 sigma.

It is planned to match the area covered by It is planned to match the area covered by OSGM02OSGM02– SW 012°W, 48°NSW 012°W, 48°N– SE 004°E, 48°NSE 004°E, 48°N– NE 004°E, 62°NNE 004°E, 62°N– SE 012°W, 62°NSE 012°W, 62°N

Work is in hand to put out the contract and Work is in hand to put out the contract and it is anticipated we will have a working it is anticipated we will have a working model for research purposes by early 2007.model for research purposes by early 2007.

This could be done using modern satellite This could be done using modern satellite data – expected accuracy +/- 0.2m 1 sigma.data – expected accuracy +/- 0.2m 1 sigma.

It is planned to match the area covered by It is planned to match the area covered by OSGM02OSGM02– SW 012°W, 48°NSW 012°W, 48°N– SE 004°E, 48°NSE 004°E, 48°N– NE 004°E, 62°NNE 004°E, 62°N– SE 012°W, 62°NSE 012°W, 62°N

Work is in hand to put out the contract and Work is in hand to put out the contract and it is anticipated we will have a working it is anticipated we will have a working model for research purposes by early 2007.model for research purposes by early 2007.


Developing the VORFDeveloping the VORFDeveloping the VORFDeveloping the VORF

1.Develop a mean sea surface using 1.Develop a mean sea surface using satellite altimetry and geoid modellingsatellite altimetry and geoid modelling

2.Use tidal modelling to derive minimum 2.Use tidal modelling to derive minimum sea surfacesea surface

1.Develop a mean sea surface using 1.Develop a mean sea surface using satellite altimetry and geoid modellingsatellite altimetry and geoid modelling

2.Use tidal modelling to derive minimum 2.Use tidal modelling to derive minimum sea surfacesea surface


Satellite Altimetry - Ground Satellite Altimetry - Ground TracksTracks

Satellite Altimetry - Ground Satellite Altimetry - Ground TracksTracks

• TOPEX/POSEIDON ground track

• Along track spacing 6-7 km

• Across track spacing 315km

• Additional data from other satellites

• ENVISAT

• ERS2

• Future satellites – 200km wide swath

“Can be likened to the deployment of thousands of tide

gauges across the ocean”


Tidal ModellingTidal ModellingTidal ModellingTidal Modelling

Once this MSL has been established the new minimum Once this MSL has been established the new minimum sea surface will be derived using tidal models provided sea surface will be derived using tidal models provided by Proudman Oceanographic Laboratory, POL.by Proudman Oceanographic Laboratory, POL.

Once this MSL has been established the new minimum Once this MSL has been established the new minimum sea surface will be derived using tidal models provided sea surface will be derived using tidal models provided by Proudman Oceanographic Laboratory, POL.by Proudman Oceanographic Laboratory, POL.


VORF Project LatestVORF Project LatestVORF Project LatestVORF Project Latest

Notice placed in the OJEU, inviting expressions Notice placed in the OJEU, inviting expressions of interest in the VORF project.of interest in the VORF project.

Tenders were submitted and have been Tenders were submitted and have been evaluated.evaluated.

Contract has been let with UCL.Contract has been let with UCL.

Notice placed in the OJEU, inviting expressions Notice placed in the OJEU, inviting expressions of interest in the VORF project.of interest in the VORF project.

Tenders were submitted and have been Tenders were submitted and have been evaluated.evaluated.

Contract has been let with UCL.Contract has been let with UCL.


Other Vertical Datum Other Vertical Datum Separation ModelsSeparation Models

Other Vertical Datum Other Vertical Datum Separation ModelsSeparation Models

The UKHO methodology is only one of The UKHO methodology is only one of the many ways to develop a vertical the many ways to develop a vertical datum separation modeldatum separation model

The UKHO methodology is only one of The UKHO methodology is only one of the many ways to develop a vertical the many ways to develop a vertical datum separation modeldatum separation model


Canadian ExampleCanadian ExampleCanadian ExampleCanadian Example The Canadian Hydrographic Service The Canadian Hydrographic Service

have used satellite altimetry and tidal have used satellite altimetry and tidal models to develop a Chart Datum models to develop a Chart Datum model offshoremodel offshore

The Canadian Hydrographic Service The Canadian Hydrographic Service have used satellite altimetry and tidal have used satellite altimetry and tidal models to develop a Chart Datum models to develop a Chart Datum model offshoremodel offshore

45.60

45.20

44.80

-66.00 -65.60 -65.20 -64.80 -64.40 -64.00 -63.60

145

65

320

325

315

312

305288

280

270

260235

240

242

245 247250

255

NOTE: Bathymetry in this areais reduced to Maitland L.W.(Chart Datum), which is 18ft.above L.W. at Burntcoat Head.

Contours represent the ellipsoidalheight of chart datum relative toNAD83 reference ellipsoid. Thesurface is constructed using a krigingmodel that honors each data pointexactly.65 Saint John

145 Alma235 West Advocate240 Cape D'Or242 Spencer's Island245 Port Greville247 Diligent River250 Cape Sharp255 Parrsboro260 Five Islands

300

270 Burntcoat Head280 Hantsport288 Pereau290 Blomidon300 Scots Bay305 Baxter's Head312 Isle Haute315 Margaretsville320 Parker's Cove325 Digby

Longitude


US ExampleUS ExampleUS ExampleUS Example

In Tampa Bay NOAA In Tampa Bay NOAA developed a Chart developed a Chart Datum model using Datum model using a hydrodynamic a hydrodynamic tidal model and a tidal model and a known relationship known relationship to NAD83 (a US to NAD83 (a US realisation of realisation of WGS84).WGS84).

In Tampa Bay NOAA In Tampa Bay NOAA developed a Chart developed a Chart Datum model using Datum model using a hydrodynamic a hydrodynamic tidal model and a tidal model and a known relationship known relationship to NAD83 (a US to NAD83 (a US realisation of realisation of WGS84).WGS84).


Keep the Goal in MindKeep the Goal in MindKeep the Goal in MindKeep the Goal in Mind Don’t create a high accuracy, expensive Don’t create a high accuracy, expensive

model if a lower accuracy one will suffice – model if a lower accuracy one will suffice – keep in mind the purpose of the modelkeep in mind the purpose of the model

What area will the model cover?What area will the model cover? Have neighbouring nations already Have neighbouring nations already

developed similar models which can be developed similar models which can be extended?extended?

Is the aim to re-create Chart Datum or Is the aim to re-create Chart Datum or develop a model of the minimum sea develop a model of the minimum sea surface?surface?

What resources are available?What resources are available? What storage requirements will the model What storage requirements will the model

have?have? How will the model be maintained? How will the model be maintained?


ConclusionsConclusionsConclusionsConclusions

Seamless vertical data is vital to Seamless vertical data is vital to future hydrographic requirements.future hydrographic requirements.

Chart Datum is not seamless and Chart Datum is not seamless and data must be referred to another data must be referred to another vertical datum. This can be via a vertical datum. This can be via a vertical datum separation model.vertical datum separation model.

The challenge is to develop this The challenge is to develop this model so that historic, current and model so that historic, current and future data can be merged.future data can be merged.

Seamless vertical data is vital to Seamless vertical data is vital to future hydrographic requirements.future hydrographic requirements.

Chart Datum is not seamless and Chart Datum is not seamless and data must be referred to another data must be referred to another vertical datum. This can be via a vertical datum. This can be via a vertical datum separation model.vertical datum separation model.

The challenge is to develop this The challenge is to develop this model so that historic, current and model so that historic, current and future data can be merged.future data can be merged.


Thank you for Thank you for listeninglisteningThank you for Thank you for listeninglistening

Ruth AdamsRuth Adams

UK Hydrographic OfficeUK Hydrographic Office

Ruth AdamsRuth Adams

UK Hydrographic OfficeUK Hydrographic Office

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United Kingdom Hydrographic Office Relating Data to a Seamless Vertical Reference Surface Ruth...

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