The establishment of primary gravimeter bases in Canada

In 1952 the Dominion Observatory initiated a program to establish throughout Canada a network of well connected primary gravimeter base stations for the control and adjustment of existing and future gravimeter surveys. A total of two hundred and seyenty bases occupied during the summer forms two separate networks, one in northern Canada and the other in southern Ontario and Quebec. In the course of the survey gravimeter measurements were made at all available pendulum stations and the results show that the standard deviation of most pendulum determinations is about 1.2 mgals., and that the worst errors are in the measurements made before 1936 and in those throughout the unsettled regions of northern Canada. The comparisons provided the calibration factor for the North American gravimeter to an accuracy of one part in a thousand. The principal facts for all the gravimeter bases and the descriptions of the sites for twenty-four principal bases in Ontario and Quebec are given. The adopted values of gravity for the bases have random errors estimated to be 0.08 mgals. and 0.15 mgals. for the southern and northern networks respectively. They may also contain systematic errors (0.5 mgals. maximum) due to the unreliability of the calibration of the gravimeter.