1 of 15

Canada’s Geodetic Reference Frames:Geometric and Vertical

2015 Geospatial Summit

Marc VéronneauCanadian Geodetic Survey, Surveyor General

Branch

2 of 15

Geometric Reference Frame (Canada)… 3

Vertical Reference Frame (Canada)… 6

Questions?… 15

Outline

3 of 15

Geometric Reference Frame (Canada)

• Canadian Geodetic Survey publishes coordinates in NAD83(CSRS) v6 epoch 2010.0.o Each province adopted a specific version/epoch (e.g., Quebec and New Brunswick use

NAD83(CSRS) v2 epoch 1997.0).o Provinces can upgrade to a newer version when they are ready.

• Canadian Geodetic Survey has no plans to replace NAD83(CSRS).

• Canadian Geodetic Survey is collaborating with the National Geodetic Survey in the realization of the new (North) American geometric reference frame.

• Canadian Geodetic Survey will publish coordinates in the new geometric reference frame o Station reports, NRCan’s CSRS-PPP, TRX software.

4 of 15

Geometric Reference Frames

ITRF88ITRF89ITRF90ITRF91ITRF92ITRF93ITRF94ITRF96ITRF97ITRF2000ITRF2005ITRF2008ITRF2014*

NAD83(NSRS/CSRS)Latitude, Longitude

and Ellipsoidal Height

NAD83(Original)Latitude and Longitude

North American FramesNAD27

Latitude and Longitude

CanadaNAD83(CSRS) v6 e. 2010.0

USANAD 83(2011) e. 2010.0

ITRF20xx/NAD 2022

* scheduled for 2015

Grid transformationParameter transformation

Equivalent

International Frames

5 of 15

Station Report (Example)

Select reference frame (NAD83(CSRS))New reference frame would be added to the drop-box list

Velocities of the station with respect to the reference frame

Height of the station from adjustment of the levelling network

Height from GNSS and selected geoid model

Select coordinates type (geographic)

Select a hybrid or gravimetric geoid model (CGG2013)

Select epoch (2010.0)

6 of 15

Vertical Reference Frame (Canada)• Canada adopted CGVD2013 in November 2013.

o Defined by a specific equipotential surface (W0 = 62,636,856 m2/s2)o Realized by a geoid model (CGG2013)o Compatible with GNSS technology

• Canada adopted a geoid-based vertical datum because …o Cost in maintaining and expanding a levelling network for a country as vast as Canadao No access to CGVD28 in remote regionso New technologies available (e.g., GNSS, satellite gravimetry)o Distortions in CGVD28 (~1.2 m at the national scale)

• Canada has the support from the provinces in the implementation of the new vertical reference system.

• Overall, Canadian users acknowledge that the benefits of a geoid-based datum outweigh disadvantages [HAL report, 2006]. o Main concerns relate to cost in converting legacy data, and confusion in heights

7 of 15

Vertical Reference Frame (Canada)• CGVD28 continues to co-exist with CGVD2013 during the transition

periodo Readjustment of the levelling network with constraints to coincide with CGVD2013;

Publish bench marks in CGVD2013 and CGVD28; GNSS-derived orthometric heights prevail over the heights from the levelling adjustment.

o CGS stopped maintenance of the bench marks of the national first-order levelling network since 2002; Bench marks are not maintained by GNSS observation either.

o CGS cannot confirm stability of the bench marks.

• Canada’s geodetic infrastructureo ~90 continuously tracking reference stations (federal/provincial)o ~200 force-centered pillars (passive stations)o Provincial High Precision Networks, Commercial RTK

• Use of CGVD2013 (still early stage)o Federal agencies (e.g., NRCan (floodplain mapping), Transport (airport), Environment

Canada (inland water; transboundary waters))o Provincial agencies initiated migration to CGVD2013

8 of 15

North American Vertical Datums (Now)

CGVD28 (Levelling; GNSS/HTv2.0) => CGVD2013 (Geoid model)

NAVD 88 (Levelling; GNSS/Geoid12A)

IGLD 85(Levelling)

Courtesy of the International Joint Commission

Transboundary Waters

9 of 15

North American Vertical Datum (Objective)

Geoid Model

W 0 = 62,636,856 m

2 /s2

• A unified height system for North America based on the equipotential surface:

• W0 = 62,636,856 m2/s2

• This surface is materialized by a geoid model which integrates satellite, airborne, and surface gravity data.

• CGS and NGS agreed on this definition.• This definition is already adopted in Canada

(CGVD2013).• Mexico and countries in Central America and

Caribbean agreed on this definition.• Coordinating Committee for the Great Lakes

and St-Lawrence River System proposed to define IGLD2020 on this surface.

• IERS and IAU had already adopted this reference surface in their conventions.

10 of 15

Canada’s Levelling network

1906-1928 1929-1939 1940-1965 1966-1971 1972-1981 1982-1989 1990-2007

Constraints

: Continental (32)

: Newfoundland (4)

: Prince Edward Island (1)

: Iles de la Madeleine (1)

: Ile d’Anticosti (1)

: Vancouver Island (2)

: Gauges (12)

11 of 15

Active Stations Processed at CGS

12 of 15

The difference between NAVD 88 and CGVD2013

HCGVD2013 – HNAVD 88

Conversion between NAVD 88 and CGVD2013o Conduct a GNSS survey on bench marks having NAVD 88 elevationo Published elevations at common bench markso GEOID12A - CGG2013 (above image)

C.I.: 10 cm

13 of 15

CSRS-Precise Point Positioning (PPP): Process GPS RINEX files to provide stand-alone coordinates (latitude, longitude, ellipsoidal height and orthometric height). Works any where in the world. [on-line]

GPS-H: Convert ellipsoidal heights to orthometric heights (makes use of any geoid models, works with different types of coordinate systems (geographic, UTM, MTM and Cartesian), and different geometric reference frames (NAD83(CSRS) and ITRF)). Could also convert between vertical datums. [on-line and desktop]

TRX: Transform coordinates between different geometric reference frames (e.g., NAD83(CSRS), ITRF), epochs and coordinate systems (e.g., geographic, UTM, MTM, Cartesian). [on-line and desktop]

Some NRCan’s tools

14 of 15

Height: 101.61 mPrecision: ± 0.01 mEpoch: 2013.2Type of height: OrthometricHeight system: CGVD2013Height frame: CGG2013

H = 23.126 ± 0.007 m CGVD2013(CGG2013) Epoch 2013.2

Labelling Heights

• Type of height: Orthometric (H), dynamic (Hd), normal (Hn), ellipsoidal (h), geoid (N)• Height Reference System: NAD83, ITRF, CGVD28, CGVD2013, NAVD 88• Height Reference Frame: CSRS v., Geoid model• Precision (e.g., ± 0.05 m)• Epoch (e.g., 2012.75)

HHeight: 91.256 mPrecision: ± 0.007 mEpoch: 2013.2Type of height: Ellipsoidal (geodetic)Height system: NAD83Height frame: CSRS (version if available)

h = 23.126 ± 0.007 m NAD83(CSRS) Epoch 2013.2 h

Geoid Height: -10.354 mPrecision: ± 0.015 mEpoch: StaticModel: CGG2013Frame: NAD83(CSRS)

N = -10.354 ± 0.015 m CGG2013, NAD83(CSRS)

N

15 of 15

NRCan Contacts: Philippe Lamothe (phlamoth@nrcan.gc.ca) Marc Véronneau (marcv@nrcan.gc.ca) Mike Craymer (craymer@nrcan.gc.ca)

General information: Web:

http://www.nrcan.gc.ca/earth-sciences/geomatics/geodetic-reference-systems/10781

Email: information@geod.nrcan.gc.ca Phone:  1-613-793-2102

QUESTIONS?