See also: Point data format description

Gravity anomaly data show variations in the gravity field caused by lateral variations in the density of the Earth's crust and upper mantle that reflect variations in composition and thickness. Systematic gravity mapping began in Canada in 1944 and is ongoing. All data are tied to the International Gravity Standardization Network 1971. Local gravity anomalies result from the juxtaposition of relatively high- and low-density rock types. Longer wavelength anomalies such as the gravity low over the Cordillera and the relative gravity high over oceanic crust largely reflect variations in the thickness of the crust.

This dataset presents Bouguer gravity anomalies on land and free-air gravity anomalies offshore. The data were compiled from the holdings of the Canadian Geodetic Information System maintained by the Geodetic Survey Division, Geomatics Canada. They were collected to map the variation in gravitational attraction over the Canadian landmass and offshore areas. Variations in the force of gravity are due to variations in the mass of underlying materials. These data are useful for geological interpretation and have applications in oil, gas, and mineral exploration. The gravity field is also used to define the geoid, which is the ideal shape of the Earth, or mean sea level if the Earth were completely covered with water.

This dataset consists of approximately 678 000 gravity observations, including 165 000 on land, acquired between 1944 and 2003. The data spacing ranges from less than 1 km to over 20 km, with an average spacing between 5 and 10 km. All measurements were reduced to the IGSN71 datum. Theoretical gravity values were calculated from the Geodetic Reference System 1980 (GRS80) gravity formula. The observation's coordinates are referred to NAD83. Bouguer anomalies were calculated using a vertical gravity gradient of 0.3086 mGal·m^-1 and a crustal density of 2 670 kg·m^-3. Areas on land are represented by Bouguer anomalies and areas offshore, by free-air anomalies.

Anomaly computation formulae

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