In 1902, in the basement of the old Supreme Court building in Ottawa, Otto Klotz, Assistant Director of the Dominion Observatory, made the first Canadian observation of gravity. He used a Mendenhall double pendulum apparatus recently acquired from Washington. This marked the start of over a century of gravity observations across Canada by the Dominion Observatory, which became the Earth Physics Branch in 1970 and merged with the Geological Survey of Canada in 1986.
The Dominion Observatory was principally involved in establishing the framework for accurate positioning across Canada. Klotz, however, recognized that spatial variations in gravity not only affected the accuracy of all levelling instruments, but also provided unique information about the density and gravitational attraction of the underlying geology. By 1915, there was a chain of 25 gravity observations stretching across Canada from New Brunswick to British Columbia.
Since 1902, hundreds of thousands of surface, marine, airborne, and satellite gravity measurements have been made, and they provide a detailed picture of Canada’s gravitational field. Applications of this information include defence, satellite navigation, geodesy, geological mapping, and exploration for oil, gas, and minerals.
Category: Science Advances
Hodgson, J.H., 1989. The Heavens Above and the Earth Beneath, A History of the Dominion Observatories: part 1, to 1946; Geological Survey of Canada, Open File 1945, 193 p. doi:10.4095/130751