The Canadian Geodetic Survey (CGS) maintains the national standards used to reference positioning (latitude, longitude and height) and gravity across Canada. These standards ensure that mapping, surveying, engineering and other location-based activities use consistent and reliable coordinates.
Coordinates and gravity values can change over time. Some changes come from updates to the reference systems or the reference frames used in Canada. Other changes occur naturally, such as crustal motion, earthquakes or gradual uplift from glacial isostatic adjustment. To help users understand these changes, all CGS data include metadata that identify the reference system, reference frame and epoch used.
This page describes the reference systems and reference frames currently used by CGS and provincial geodetic agencies. It also explains how these systems are updated and how natural ground motion of the Earth affects coordinates.
Definition
A reference system is the theoretical definition of how positions or heights are measured. It includes the origin, scale, orientation and mathematical parameters of the coordinate system.
A reference frame is the physical realization of a reference system. It is defined by the published coordinates or gravity values assigned to control points, as well as the models used to support those values. Because new observations, improved models and natural ground motion can change these values over time, reference frames are updated more often than reference systems.
A reference system defines the rules.
A reference frame applies those rules to estimate real coordinates.
Geometric component
Canada uses the North American Datum of 1983 (NAD83) as its geometric reference system. This system defines how latitude, longitude and ellipsoidal heights are measured across the country. Its Canadian realization, known as the Canadian Spatial Reference System (CSRS), provides the foundation for positioning used in mapping, surveying and other geospatial applications.
The current realization of this system is NAD83(CSRS) v8. This version includes updated coordinates and velocities for the Canadian Active Control System (CACS) and the Canadian Base Network (CBN). It reflects new GNSS observations, reprocessed historical data, improvements to modelling, and adjustments for surface motion such as earthquakes. Although differences between NAD83(CSRS) versions are generally small, each update provides a more accurate and consistent reference for users. As part of maintaining this reference frame, CGS updates NAD83(CSRS) when new realizations of the International Terrestrial Reference Frame (ITRF) are released. Each ITRF realization incorporates improved global observations and modelling. Aligning NAD83(CSRS) with these updates allows Canada to remain consistent with international reference systems and ensures that national coordinates reflect the best available data.
Coordinates in NAD83(CSRS) are tied to specific epochs to account for the ongoing motion of the Earth’s crust. This includes long-term changes from processes like glacial isostatic adjustment, as well as short-term movements caused by events such as earthquakes. CGS monitors this motion using continuous GNSS observations and periodic re-observations of control monuments. Publishing coordinates at defined epochs helps ensure that datasets produced at different times remain consistent.
NAD83(CSRS) also includes a velocity model that describes how points move over time. This information supports the transformation of coordinates between epochs and helps users maintain accuracy in applications where geospatial datasets were collected at different times. Updated velocity models are released with each new realization.
The geometric reference frame relies on two national control networks: the continuously operating CACS stations and the monumented CBN network. Regular updates to these networks support improvements in accuracy and the development of future realizations.
A new geometric reference system, the North American Terrestrial Reference Frame of 2022 (NATRF2022), is being developed in North America. CGS works with international partners to support consistency along the Canada–U.S. boundary. Further information about system updates will be provided on the modernization webpage as it becomes available.
Summary of NAD83 realizations in Canada
| Version (epoch) | Frame | Adopted | Based on |
|---|---|---|---|
| v0 Original | 1986 - 1993 | Horizontal adjustments | |
| v1 (1997.0) | CSRS96 | 1996 | Transformation from ITRF94 |
| v2 (1997.0) | CSRS98/CSRS | 1998 | Transformation from ITRF96* |
| v3 (1997.0) | 2000 |
Transformation from ITRF97 (first CBN) |
|
| v4 (2002.0) | 2002 | Transformation from ITRF2000 | |
| v5 (2006.0) | 2009 | Transformation from ITRF2005 | |
| v6 (2010.0) | 2012 | Transformation from ITRF2008 | |
| v7 (2010.0) | 2019 | Transformation from ITRF2014 | |
| v8 (2010.0) | 2024 | Transformation from ITRF2020 |
* Definition of NAD83(CSRS = CSRS98)
Vertical component
Canada’s height reference system is the Canadian Geodetic Vertical Datum of 2013 (CGVD2013). This system, approximating mean sea level, defines how elevations are measured across the country. CGVD2013 replaced the older CGVD28 datum and corrected several long-standing inconsistencies. Unlike earlier height systems that relied on a network of levelled benchmarks, CGVD2013 is realized through a gravimetric geoid model, which allows users to obtain consistent heights from GNSS observations.
The current realization of this system is CGVD2013(CGG2013a), which uses the CGG2013a geoid model to define heights. This model was introduced in 2015 as an update to the original CGG2013 model and includes regional improvements based on additional gravity data and refined modelling. CGS continues to collect new gravity measurements and improve geoid modelling, although updates are only released when recommended by the Canadian Geodetic Reference System Committee (CGRSC).
Canada works closely with partners in the United States and Mexico to support consistency along shared borders. A new static geoid model for North America, known as SGEOID2022, has been developed to provide a common reference surface across the continent. In Canada, SGEOID2022 will serve as the basis for the next realization of CGVD2013. The height reference system itself will remain CGVD2013; only the realization will be updated.
CGS will continue to provide information and transition guidance as new geoid models become available. Users can expect the height reference system to remain stable, with updates focused on improving accuracy and maintaining consistency across jurisdictions.
Gravity component
Canada’s gravity reference system is maintained through the Canadian Gravity Standardization Network (CGSN). This network provides the reference values used for gravity measurements across Canada. The current system is tied to the International Gravity Standardization Network of 1971 (IGSN71), which has served as the global gravity reference for several decades.
CGS is working to improve the national gravity network by incorporating new gravity measurements and updated modelling. These improvements will increase accuracy and support future geoid development. The next adjustment to the network will align gravity values to epoch 2020.0 and include a velocity model that describes small changes in the gravity field through time. This updated realization will likely be known as CGSN2020.
While enhancements are underway, the existing gravity reference system remains in use, and users can continue to rely on current published gravity values. Any updates to the gravity system or its realization will be communicated once finalized.
Updates and upcoming changes
CGS continues to improve the accuracy of Canada’s reference frames through updated observations, improved modelling and refinements to national control networks. Recent updates include the release of NAD83(CSRS) v8, which provides revised coordinates and velocities for many control stations.
Work continues in North America to develop new geometric and vertical reference systems. In Canada, any future changes will be communicated in advance, and detailed information will be provided on the Modernization of Canada’s Spatial Reference System webpage when available.