observe, collect, predict
1 / 25

Authors: Phillip MacAulay (CHS) macaulayp@mar.dfo-mpo.gc - PowerPoint PPT Presentation

  • Uploaded on

observe, collect, predict. WebTide. LAT wrt MWL. Authors: Phillip MacAulay (CHS) macaulayp@mar.dfo-mpo.gc.ca Charles O’Reilly (CHS) oreillyc@mar.dfo-mpo.gc.ca Keith Thompson (Dalhousie) keith.thompson@dal.ca. PWLN.

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
Download Presentation

PowerPoint Slideshow about 'Authors: Phillip MacAulay (CHS) macaulayp@mar.dfo-mpo.gc' - jory

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Authors phillip macaulay chs macaulayp mar dfo mpo gc

observe, collect, predict



Authors: Phillip MacAulay (CHS) macaulayp@mar.dfo-mpo.gc.ca

Charles O’Reilly (CHS) oreillyc@mar.dfo-mpo.gc.ca

Keith Thompson (Dalhousie) keith.thompson@dal.ca


Atlantic Canada’s Real-Time Water Level SystemObservations, Predictions, Forecasts and Datums on the Web

RTWL System

3D Continuous datums


Dalcoast II


zero phase shift, multi band pass,

recursive filter

Chs atlantic s permanent water level network


Long Term Sea Level (GLOSS)

Tsunami Gauges

Storm Surge Gauges
















CHS Atlantic’s Permanent Water Level Network

16 tide gauges, 000’s kms of coastline

Presentation Subtext:Socio-economic and Hydrographic motivations for maintaining

coastal water level monitoring programs and networks

Authors phillip macaulay chs macaulayp mar dfo mpo gc

PWLN Equipment and Operational Upgrades

Who is


1) Legacy Sensor:

Continuous chain float and pulley with optical encoder and tungsten weight, specific gravity =18

2) Secondary Sensor:

Continuous fast response bubbler

3) Backup Sensor:

Submersible pressure sensor

4) Laser sensor:














  • New Versatile Sutron XPert Dataloggers

  • Backup Communications

    GOES Satellite Systems (need 10 min permission)

  • High Frequency Water Level Measurements and Gauge Polling

    1 minute averaged sampling, 10 minute gauge polling, average 5 min data latency

  • Sutron XConnect real time data collection software

  • Redundant Sensors

    Primary Rotary Encoder

    (Stable, Accurate, Reliable)

    Secondary Bubbler

    (Stable, Secondary Backup)

    Tertiary Pressure sensor

    (Extreme Water Levels,

    Fast Response Wells, Tertiary Backup)

    Laser sensor

    (Stable, Highly Accurate,

    Direct Independent Measurement

    Testing for GLOSS sites)

Schematic of the atlantic rtwl system a collaborative effort

DFO Science

(Matlab, Modeling)

RTWLOracle Dbase

Schematic of the Atlantic RTWL SystemA Collaborative Effort

PWLN Tide Gauges


Archival Data

GOES Satellite link

GOES Satellite Download

XConnect Backup

Data Acquisition PC (XConnect)

CHS XP Network




Water Level Clients


Dalcoast II


DFO Science




Real time data

Data Backup

DFO web server,

RTWL web pages

Rtwl web pages
RTWL Web Pages

Kohila Thana, Science Informatics

Examples of other real or quasi real time systems
Examples of other Real or Quasi-Real Time Systems

  • National Oceanographic and Atmospheric Administration’s (NOAA) Tides and Currents web site ----Physical Oceanographic Real-Time System (PORTS)

  • European Sea Level Service (ESEAS)

  • Monitoring Network System for Systematic Sea Level Measurements in the Mediterranean and Black Sea (MedGLOSS)

  • UK National Tidal and Sea Level Facility (NTSLF)

Observations constituent predictions the residual
Observations, Constituent Predictions, The Residual

The Residual: Observations – Predictions (non-tidal behavior)

  • Weather (storm surges, positive and negative)

  • Departures at tidal frequencies (variations in the tidal constituents)

  • Everything else affecting water level variations (infra-gravity waves, harbour seiches, tsunamis, shelf waves …)

North Sydney, NS

St. Lawrence, NFLD

  • Timescales (minutes to months)

  • Reason for continued monitoring of coastal water levels (Presentation Subtext)

  • Immediate impact on coastal environments, populations, and infra-structure

  • Danger to navigation

  • Validate storm surge models

Forecasting the residual

x1, x2, ….,xt equispaced scalar values to be filtered

Tide gauge


st denote an auxiliary state vector

Forecasting the Residual

  • Effects of weather

    Dalcoast II -- 2D, barotropic, non-linear, lateral diffusion, 1/12o ,forced by EC 3hr winds and pressure (48hr surge forecast, once per day)

  • Everything else

    Spectral-nudging Kalman Filter (Thompson etal., 2006)

    -- zero phase shift, multi band pass, recursive filter

Build Term

Decay Term


Filter band pass width,

gain, (spin up period)-1


Bias term

Bobanovic and Thompson, 2001

Band Pass





Proto-Forecast = Constituent Predictions + timeseries of 0-24 hr surge + 24-48 hr surge

Forecast model residual error = Observations (up to last) – (Proto-Forecast)

Residual error Nowcast = Filter (forecast model residual error), *Nowcast mode, build/modify state vector energy

Residual error forecast = Filter, *Forecast mode, project existing state vector energy into the future (no decay)

Final forecast = Proto-forecast + residual error nowcast and forecast

Selection of filter frequencies and gains
Selection of Filter Frequencies and Gains

  • From Theory: Diurnal O1, Semidiurnal M2

    gain/filter band widths wide enough to capture other diurnal and semidiurnals

  • From Recent Observations (analysis of forecast model residual error timeseries):

    Upper Tidal and Seiche Frequencies, gain/decay timescales ~ 1.5 to 2 wave periods

Forecast model residual error

Seiche content

Seiche energy/frequencies

Residual tidal energy/frequencies

Example forecast
Example Forecast



Operational code under testing,

Available on RTWL web pages soon


Continuous datums for atlantic canada

Dynamical Modeling

Gridded Surfaces

Discrete Calculation

Continuous Datums for Atlantic Canada

  • What are they? Where are we starting from?

  • Why do we need them?

  • Where are we in Atlantic Canada?

  • How should we now best proceed?

  • Planning, Development Stage

    Although in principal prototypical versions have already used

    • 06-07 Labrador route survey Webtide

    • 07 Northumberland Strait Survey Webtide

    • 07 Fundy Survey Webtide, Omnistar

Long timescale wl monitoring vertical control datum management

2D Simplification












Tidal range






Continuous Surface Honoring

Discrete Control








Growing systematic errors

Stn 0491

Lat, Long

Discrete Vertical Control,

Tide stations

Spatially variable tidal properties

Sea bed


<30 cm

Long Timescale WL MonitoringVertical Control Datum Management

  • Hydrographic reason to maintain a minimal, effective water level monitoring network/program, maintain/track tidal datums wrt relative sea level rise

    (Presentation Subtext)

  • Present and past approach, What are continuous Datums?

    Constant Datum Transform Assumption (CDTA)

Why do we need them
Why do we need them?

  • With GPS based vertical positioning, RTK or modeled (Omnistar), errors introduced to charts by the CDTA can become significant part of vertical error.

  • CDTA can be inappropriate some activities:

    • route surveys

    • surveys where tidal target surfaces change significantly over survey scale (estuaries, Bay of Fundy)

    • Flood mapping of large areas

    • RTK solutions and Anywhere, anytime water level

      applications (WebTide), Continuous applications need

      continuous datums

Multi-constiuent, anywhere tidal prediction


Constituents derived from a Hydrodynamic Barotropic Ocean Model

Assimilating Topex Posieden Altimeter data

Dupont, F., C.G. Hannah, D.A. Greenberg, J.Y. Cherniawsky and C.E. Naimie.  2002. 

Modelling system for tides for the North-west Atlantic coastal ocean. [online].

[Accessed 21 April, 2008]. Available from World Wide Web: http://www.dfo-mpo.gc.ca/Library/265855.pdf

Distance weighted datum transform mwl to cd discrete calculation

Location transform






Coastal datum

control points




Ti – transform at i

tj – transform at j

wj – weight for tj


Distance weighted datum transform MWL to CD (Discrete calculation)

Webtide provides anytime, anywhere tidal prediction wrt to a floating MWL

We want tidal prediction wrt CD, need anywhere transform between MWL and CD

Herman Varma

Exponent p determines local flatness

and width of transition zone

  • Used in:

  • Labrador 06-07

  • Northumberland 07

  • Fundy 07

How should we best proceed
How should we best proceed?

  • Closely examine the programs and methods employed by others, NOAA/NOS, UK (Excellent Workshop Monday)

  • Develop plans of approach (brainstorm, communicate needs/requirements

  • Discuss options with Datum clients

  • Develop project outlines/proposals

  • Acquire necessary resources and get on with it

How should we best proceed concept outline for an atlantic plan
How should we best proceed?Concept outline for an Atlantic Plan

  • Develop an initial theoretical target surface

    example: LAT as Sum of WebTide constituent amplitudes

WebTide is based around a floating MWL, thus a surface computed from it must then be referenced to observed mean water levels. MWL is better known at some shore based locations than others. Away from the coast we must rely on either satellite altimetry or Geodetic models.

Authors phillip macaulay chs macaulayp mar dfo mpo gc

How should we best proceed?Concept outline for an Atlantic Plan

  • Compare existing shore-based Datum reference points to theoretical target surface. There will be misfit. Find and identify poor reference control, iteratively adjust target surface to more closely honor high quality shore-based reference control. Iterations between steps 1 and 2 may be necessary.

Authors phillip macaulay chs macaulayp mar dfo mpo gc

How should we best proceed?Concept outline for an Atlantic Plan

  • Adjust or supersede the target surface where good surrounding shore-based reference Datums permit independent surface estimation. Sequester inshore areas requiring further data or modeling. (NULL datum concept)

  • Calculate the seamless Datum surface grid. Grid spacing could be variable based on the local rate of change of the Datum surface.

  • Agree on standardized methods for interpolation between datum surface grid points and thus calculation of all Datum transformations.

  • Transform Dissemination tools?

    For Hydrographic work? Public? (VDatum?)

  • Border transitions? regional (Atlantic/Quebec), international (Atlantic/US)

Combination of the 3D Datum surfaces with WebTide will yield an anytime, anywhere, on Datum water level prediction/sounding reduction tool.

Authors phillip macaulay chs macaulayp mar dfo mpo gc


  • Savi Narayanan, CHS directorate, direction and funding

  • John Loder, expertise on tsunami gauge locations

  • John O’Neill and Kohila Thana, system and web design

  • Mike Ruxton, Craig Wright, Larry Norton, Mark McCracken, James Hanway, CHS Geomatics

  • Steve Parsons, Herman Varma, Chris Coolen, Fred Carmichael, CHS Atlantic

  • CHS Quebec, Pacific and Central and Arctic

  • Carmen Reid, Canadian Coast Guard

Authors phillip macaulay chs macaulayp mar dfo mpo gc

Higher High Water

High Water


Low Water

Lower Low Water

NOS Generation of Tidal Datum Fields

• MHW tidal datum fields (as well as MHHW, MLW, MLLW, MSL, MTL, DTL) from calibrated hydrodynamic models

• Analysis of model-produced time series, then adjusted to provide a best fit to datums at NOS gauges.

Authors phillip macaulay chs macaulayp mar dfo mpo gc

Vertical Datum Transformations in VDatum

Tidal Datums

MLLW Mean Lower Low Water

MLW Mean Low Water

LMSL Local Mean Sea Level

MTL Mean Tide Level

DTL Diurnal Tide Level

MHW Mean High Water

MHHW Mean Higher High Water

Orthometric Datums

NAVD 88 North American Vertical

Datum 1988

NGVD 29 National Geodetic

Vertical Datum of 1929

3-D/Ellipsoid Datums

NAD 83 (NSRS) North American Datum 1983

WGS 84(G873) World Geodetic System 1984 (G873)

WGS 84(G730) World Geodetic System 1984 (G730)

WGS 84(orig) World Geodetic System 1984

(original system -- 1984)

WGS 72 World Geodetic System 1972

ITRF International Terrestrial Reference Frame

1988-94, 1996-98, 2000

SIO/MIT 92 Scripps Institution of Oceanography /

Mass. Inst. of Tech. 1992

NEOS 90 National Earth Orientation Service 1990

PNEOS 90 Preliminary Nat’l Earth Orientation Service 1990

Authors phillip macaulay chs macaulayp mar dfo mpo gc

VDatum Interpolation to the User Input Location

Conversion value at any location is determined by interpolation using surrounding values. For geodetic grids, set of nine points are used with bi-quadratic interpolation.

For points in tidal grid, two methods are used. If four surrounding VDatum points are non-null, bilinear interpolation is used. If 1-3 points are null value, inverse-distance-squared weighting is used for non-null values.

Rtwl initiatives 2006 07



RTWL Initiatives 2006/07

  • Link Matlab to RTWL database and web pages

    • Employ Matlab’s powerful computational engine for RTQC

    • Interactive web content using Matlab

  • Real time quality control (RTQC), tsunami detection, and water level forecasting

    • Reliability of Nowcast data on the web

    • Identification of tsunami signals

    • Water level forecasts (storm surge model)

  • Observation-based tsunami detection and warning enhancement (Sable/Hibernia)

    • Early detection/verification

    • Landfall wave height estimation, Zhigang Xu (IML)

Storm surges
Storm Surges

~1 meter storm surges during spring tides, Feb/01/2006

Potential Flooding

Simulated tsunami arrival
Simulated Tsunami Arrival

Simulated tsunami signal, Zhigang Xu (IML)