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Initiatives
The Canadian Height Modernization Initiative
The current height reference system is based on the Canadian Geodetic Vertical Datum (CGVD28), adopted in 1935, which was constructed using classical surveying techniques. The datum reference level was defined as mean sea-level determined from data collected at five tide gauges on the east and west coasts. The datum is accessed by users through an extensive network of precisely levelled benchmarks provided by government agencies. Historically, the definition of this height reference system has been separate from the definition of the horizontal reference system, but with the implementation of the Canadian Spatial Reference System, this is changing.
A number of limitations (described in technical papers provided) are associated with the continued use of CGVD28 including the cost of maintenance, coverage in remote areas, compatibility with the Canadian horizontal reference system and the height reference systems in other jurisdictions, accuracy and distortions in the system, and compatibility with modern space-based positioning technology.
GPS users require 3D positions referenced to the Canadian Spatial Reference System (CSRS) to ensure compatibility with data from other sources and to meet regulatory requirements. Therefore, the modernization of the vertical component of the CSRS is critical to providing Canadians with a truly three-dimensional integrated datum.
An opportunity exists to define a new datum that resolves the limitations of the current system - one that is compatible with international standards, enables cost-saving implementation of space-based technologies such as GPS, is easily accessible at any point in Canada, and is less sensitive to geodynamic activities and the deterioration of benchmarks. Such a system would be based on an accurate "geoid" model. More >>
