surveying on the ellipsoid: a canadianhydrographic perspective · water height reduction 𝐻...
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![Page 1: Surveying on the Ellipsoid: A CanadianHydrographic Perspective · Water Height Reduction 𝐻 w𝑙= ℎ𝑒𝑙𝑙𝑖 − 𝑁− ℎ𝑒𝑎 𝑒 𝑒 𝑒𝑙 − ℎ𝑒𝑎](https://reader033.vdocument.in/reader033/viewer/2022041700/5e40f941d5b11534b4153158/html5/thumbnails/1.jpg)
Surveying on the Ellipsoid: A Canadian Hydrographic
Perspective
Ian Church
![Page 2: Surveying on the Ellipsoid: A CanadianHydrographic Perspective · Water Height Reduction 𝐻 w𝑙= ℎ𝑒𝑙𝑙𝑖 − 𝑁− ℎ𝑒𝑎 𝑒 𝑒 𝑒𝑙 − ℎ𝑒𝑎](https://reader033.vdocument.in/reader033/viewer/2022041700/5e40f941d5b11534b4153158/html5/thumbnails/2.jpg)
![Page 3: Surveying on the Ellipsoid: A CanadianHydrographic Perspective · Water Height Reduction 𝐻 w𝑙= ℎ𝑒𝑙𝑙𝑖 − 𝑁− ℎ𝑒𝑎 𝑒 𝑒 𝑒𝑙 − ℎ𝑒𝑎](https://reader033.vdocument.in/reader033/viewer/2022041700/5e40f941d5b11534b4153158/html5/thumbnails/3.jpg)
• System Integration
• Raytracing
• Positioning (3D vs 2D)
Processing Multibeam Survey Data
Depth Sounding
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Positioning of a Depth Sounding
Depth Sounding
Horizontal Position
Vertical Position
![Page 5: Surveying on the Ellipsoid: A CanadianHydrographic Perspective · Water Height Reduction 𝐻 w𝑙= ℎ𝑒𝑙𝑙𝑖 − 𝑁− ℎ𝑒𝑎 𝑒 𝑒 𝑒𝑙 − ℎ𝑒𝑎](https://reader033.vdocument.in/reader033/viewer/2022041700/5e40f941d5b11534b4153158/html5/thumbnails/5.jpg)
Traditional Depth Sounding Position
Vertical:
Tides, Draft & Squat
Horizontal:
Positioning (GNSS)
Why are these positions from different sources?
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Vertical Positioning
• What is the vertical reference
for the numbers on a chart?
• They must be meaningful to a
mariner
http://museum.gov.ns.ca/fossils/protect/tideanim.htm24 hours worth of water-levels
Must Consider the Changing Tide
![Page 7: Surveying on the Ellipsoid: A CanadianHydrographic Perspective · Water Height Reduction 𝐻 w𝑙= ℎ𝑒𝑙𝑙𝑖 − 𝑁− ℎ𝑒𝑎 𝑒 𝑒 𝑒𝑙 − ℎ𝑒𝑎](https://reader033.vdocument.in/reader033/viewer/2022041700/5e40f941d5b11534b4153158/html5/thumbnails/7.jpg)
Ellipsoid Reference Survey (ERS)
• Find a way to transform data from the Ellipsoid to Chart Datum
• FIG #62 (Mills & Dodd, 2014)
• Know how to do it - Lots of potential ways to get the separation
![Page 8: Surveying on the Ellipsoid: A CanadianHydrographic Perspective · Water Height Reduction 𝐻 w𝑙= ℎ𝑒𝑙𝑙𝑖 − 𝑁− ℎ𝑒𝑎 𝑒 𝑒 𝑒𝑙 − ℎ𝑒𝑎](https://reader033.vdocument.in/reader033/viewer/2022041700/5e40f941d5b11534b4153158/html5/thumbnails/8.jpg)
Challenge for Canada
• Canada has a special challenge
– We need to have agreement across the country -long coastline, lots of water and limited resources
– Few tide gauges and lots of open water
• Makes interpolation of CD between gauges impossible.
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![Page 10: Surveying on the Ellipsoid: A CanadianHydrographic Perspective · Water Height Reduction 𝐻 w𝑙= ℎ𝑒𝑙𝑙𝑖 − 𝑁− ℎ𝑒𝑎 𝑒 𝑒 𝑒𝑙 − ℎ𝑒𝑎](https://reader033.vdocument.in/reader033/viewer/2022041700/5e40f941d5b11534b4153158/html5/thumbnails/10.jpg)
M2 K1
Hudson Bay M2 and K1 Amphidromes (Co-Tidal Charts) 2005 Version (WebTide)
Interpolation works well in a Narrow
Channel, but what about in an Open Bay?
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Continuously Varying Chart Datum (CVD) for Canada
Robin, C., Nudds, S., MacAulay, P., Godin, A., De Lange Boom, B., & Bartlett, J. (2016). Hydrographic Vertical Separation Surfaces (HyVSEPs) for the Tidal Waters of Canada. Marine Geodesy, 39(2), 195–222.
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Ellipsoid
Sonar-relative
Depth measurement
(Sound Velocity Correction)
Instantaneous
Water level
N: (Geoid
Model)
h:
(Ellipsoid)
GPS Approach We Need SEP (Ellipsoid – CD)
H:
(Orthometric )
SSTHydrodynamic
Model
CD
SEP
SEPSEP
Charted
Depth
CD Depth = Sonar Depth + Offsets + Ellipsoid –SEP
SEP = N + SST + HModel
![Page 13: Surveying on the Ellipsoid: A CanadianHydrographic Perspective · Water Height Reduction 𝐻 w𝑙= ℎ𝑒𝑙𝑙𝑖 − 𝑁− ℎ𝑒𝑎 𝑒 𝑒 𝑒𝑙 − ℎ𝑒𝑎](https://reader033.vdocument.in/reader033/viewer/2022041700/5e40f941d5b11534b4153158/html5/thumbnails/13.jpg)
Ellipsoid
Sonar-relative
Depth measurement
(Sound Velocity Correction)
Instantaneous
Water level
N: (Geoid
Model)
h:
(Ellipsoid)
GPS Approach We Need SEP (Ellipsoid – CD)
H:
(Orthometric )
SSTHydrodynamic
Model
CD
SEP
SEPSEP
Charted
Depth
CD Depth = Sonar Depth + Offsets + Ellipsoid –SEP
SEP = N + SST + HModel
![Page 14: Surveying on the Ellipsoid: A CanadianHydrographic Perspective · Water Height Reduction 𝐻 w𝑙= ℎ𝑒𝑙𝑙𝑖 − 𝑁− ℎ𝑒𝑎 𝑒 𝑒 𝑒𝑙 − ℎ𝑒𝑎](https://reader033.vdocument.in/reader033/viewer/2022041700/5e40f941d5b11534b4153158/html5/thumbnails/14.jpg)
Geoid-Ellipsoid Separation Models
• Canada: CGVD2013 (CGG2013)
• USA: Geoid12A: NAD83 NAVD88 (hybrid Geoid)
• USA: USGG2012: WGS84 Geoid
• International: EGM08
Geoid12A
CGVD2013
![Page 15: Surveying on the Ellipsoid: A CanadianHydrographic Perspective · Water Height Reduction 𝐻 w𝑙= ℎ𝑒𝑙𝑙𝑖 − 𝑁− ℎ𝑒𝑎 𝑒 𝑒 𝑒𝑙 − ℎ𝑒𝑎](https://reader033.vdocument.in/reader033/viewer/2022041700/5e40f941d5b11534b4153158/html5/thumbnails/15.jpg)
15
CGVD2013 Error Map
NRCAN, 2014
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CGG2013 Minus GGeoid14
Research Analysis by UNB GGE MScE Student Weston Renoud
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Resolution and Akpatok Islands
Research Analysis by UNB GGE MScE Student Weston Renoud
CGG2013 GGeoid14
Resolution and
Akpotok IslandsResolution and
Akpotok Islands
Differences of +/- 40 cm
![Page 18: Surveying on the Ellipsoid: A CanadianHydrographic Perspective · Water Height Reduction 𝐻 w𝑙= ℎ𝑒𝑙𝑙𝑖 − 𝑁− ℎ𝑒𝑎 𝑒 𝑒 𝑒𝑙 − ℎ𝑒𝑎](https://reader033.vdocument.in/reader033/viewer/2022041700/5e40f941d5b11534b4153158/html5/thumbnails/18.jpg)
Ellipsoid
Sonar-relative
Depth measurement
(Sound Velocity Correction)
Instantaneous
Water level
N: (Geoid
Model)
h:
(Ellipsoid)
GPS Approach We Need SEP (Ellipsoid – CD)
H:
(Orthometric )
SSTHydrodynamic
Model
CD
SEP
SEPSEP
Charted
Depth
CD Depth = Sonar Depth + Offsets + Ellipsoid –SEP
SEP = N + SST + HModel
![Page 19: Surveying on the Ellipsoid: A CanadianHydrographic Perspective · Water Height Reduction 𝐻 w𝑙= ℎ𝑒𝑙𝑙𝑖 − 𝑁− ℎ𝑒𝑎 𝑒 𝑒 𝑒𝑙 − ℎ𝑒𝑎](https://reader033.vdocument.in/reader033/viewer/2022041700/5e40f941d5b11534b4153158/html5/thumbnails/19.jpg)
Dynamic Ocean Topography
DOT: Associated Epoch and a Reference Geoid • Sea Surface Variations
– Ocean Currents: 1 m
– Waves
– Sun Heating: 0.3 – 1 m
– Storms, Pressure, Winds. etc
![Page 20: Surveying on the Ellipsoid: A CanadianHydrographic Perspective · Water Height Reduction 𝐻 w𝑙= ℎ𝑒𝑙𝑙𝑖 − 𝑁− ℎ𝑒𝑎 𝑒 𝑒 𝑒𝑙 − ℎ𝑒𝑎](https://reader033.vdocument.in/reader033/viewer/2022041700/5e40f941d5b11534b4153158/html5/thumbnails/20.jpg)
Ellipsoid
Sonar-relative
Depth measurement
(Sound Velocity Correction)
Instantaneous
Water level
N: (Geoid
Model)
h:
(Ellipsoid)
GPS Approach We Need SEP (Ellipsoid – CD)
H:
(Orthometric )
SSTHydrodynamic
Model
CD
SEP
SEPSEP
Charted
Depth
CD Depth = Sonar Depth + Offsets + Ellipsoid –SEP
SEP = N + SST + HModel
![Page 21: Surveying on the Ellipsoid: A CanadianHydrographic Perspective · Water Height Reduction 𝐻 w𝑙= ℎ𝑒𝑙𝑙𝑖 − 𝑁− ℎ𝑒𝑎 𝑒 𝑒 𝑒𝑙 − ℎ𝑒𝑎](https://reader033.vdocument.in/reader033/viewer/2022041700/5e40f941d5b11534b4153158/html5/thumbnails/21.jpg)
21 21
5.5
5.0
WebTide(Hannah, Greenberg, Dupont et al.)Scotian Shelf Model
M2 Amplitude
Hydrodynamic Model
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Canadian Tidal Model Coverage
➢Tides:
• Limited Tide Gauge Network
• Hydrodynamic Models
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Match the 2-Dimensionally Varying Chart Datum from Hydrodynamic Model to Established Chart Datum
23
Hydrodynamic
Model
CDCharted
Depth
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Continuous Vertical Datum
Tide stations and the four working grid domains, each portrayed
in a separate colour, duplicated from Robin et al (2016)
Accuracy estimates:
CANEAST 7.5cm
CANWEST 6.9cm
CANNORTH 6.6cm
CANHUD 17.7cm
For CGG2013 single
average error of 2.5 cm
used
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Water Levels from GNSS
Photo of the GPS-Catamaran at M2 tide gauge
location, duplicated from Bonnefond et al (2003)
CCGS Amundsen icebreaker –Wert (2004)
Princess of Acadia –Wardwell (2008)
MV AIDAblu
Duplicated from
Reinking et al
(2012)
![Page 26: Surveying on the Ellipsoid: A CanadianHydrographic Perspective · Water Height Reduction 𝐻 w𝑙= ℎ𝑒𝑙𝑙𝑖 − 𝑁− ℎ𝑒𝑎 𝑒 𝑒 𝑒𝑙 − ℎ𝑒𝑎](https://reader033.vdocument.in/reader033/viewer/2022041700/5e40f941d5b11534b4153158/html5/thumbnails/26.jpg)
RV Nuliajuk
~4
00
km
http://www.omg.unb.ca/Projects/Arctic/SE_Baffin/
Part of OMG Arctic
Mapping Program
2012-2014
Research Analysis by UNB GGE MScE Student Weston Renoud
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Water Height Reduction𝐻w𝑙 = ℎ𝑒𝑙𝑙𝑖𝑝− 𝑁 − ℎ𝑒𝑎𝑣𝑒𝑣𝑒𝑠𝑠𝑒𝑙− ℎ𝑒𝑎𝑣𝑒𝑙𝑒𝑣𝑒𝑟 − 𝑠𝑞𝑢𝑎𝑡 − ℎ𝑎𝑛𝑡
− 𝑤𝑙𝑧Where:
ℎ𝑒𝑙𝑙𝑖𝑝 - the PPP solution height above NAD83(CSRS),
𝑁 - the geoid undulation from CGG2013 for the
position of the vessel,
ℎ𝑒𝑎𝑣𝑒𝑣𝑒𝑠𝑠𝑒𝑙 - the vessel heave as reported at the ship’s
reference point,
ℎ𝑒𝑎𝑣𝑒𝑙𝑒𝑣𝑒𝑟 - induced heave due to offsets of the antenna
from the ship’s reference point,
𝑠𝑞𝑢𝑎𝑡 - vessel squat as a function of the speed over
ground,
ℎ𝑎𝑛𝑡 - height of the GNSS antenna above the ship’s
reference point, and
𝑤𝑙𝑧 - height of the ship’s reference point above the
water. Research Analysis by UNB GGE MScE Student Weston Renoud
hellip
N
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GNSS Water Height and Tide Observations
Research Analysis by UNB GGE MScE Student Weston Renoud
Comparison of GNSS Water Heights to Observations at active Tidal Station:Frobisher’s Farthest – Frobisher Bay
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Initial Results and Validation
• NRCAN PPP solutions for the forward mounted CNAV3050
were used as observations
• Estimates of Mean Sea Level wrt Ellipsoid
• Grids were binned at 3 km
Research Analysis by UNB GGE MScE Student Weston Renoud
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Conclusions
• The hydrographic community has unique challenges for vertical referencing vs. land surveying
• Ellipsoid Referenced Surveys (ERS) are now possible for all Canadian Waters
• The CVD solution must be continually refined and improved as better Geoid Approximations, DOT estimates and Tidal Estimates become available
• There needs to be additional validations throughout the CVD domain to verify stated uncertainties and to confirm that vertical accuracy requirements are being met
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Questions?