Systematic gravity mapping began in Canada in 1944 and is ongoing. The data are collected to map the variation in gravitational attraction over the Canadian landmass and offshore areas. The Canadian Geodetic Information System maintained by the Geodetic Survey Division, Geomatics Canada, holds the data. 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.

Gravity data are usually acquired using relative gravimeters that measure changes in gravity from one place to another. On the Canadian landmass, gravity has been measured at discrete stations using static gravimeters. Although measurements at some offshore stations have been taken using static gravimeters on the ocean floor, most were acquired using dynamic gravimeters aboard moving vessels. The relative nature of the gravimeters requires that the force of gravity be known at the start and end of a series of observations. The start and end points are referred to as 'base stations' or 'control stations'. The control stations used in processing the data make up the Canadian Gravity Standardization Network (CGSN). These control stations have been established from the International Gravity Standardization Network 1971 (IGSN71). Gravimeter readings are converted to gravity observations by a least squares adjustment of the readings to the control stations.

The Canadian Gravity Anomaly Data Base consists of approximately 660 000 gravity observations, including 165 000 on land, acquired between 1944 and the present. 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 1967 (GRS67) gravity formula. 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.

The Geoscience Data Repository provides access to free downloadable Gravity data