Ten Years of Experience in Converting Canadian Hydrographic Service Charts to a World-Based Geodetic Datum

As long ago as 1975, North Americans realized that the North American Datum of 1927 (NAD 27) was becoming out-dated and that it would eventually have to be replaced by a geocentric datum. The Canadian Hydrographic Service (CHS) welcomed the idea but was also fully aware that some of its charts were not even based on NAD 27. In 1986, once the framework stations became known on the North American Datum of 1983 (equivalent to the World Geodetic System of 1984), CHS started the conversion of Canadian charts to that datum. This paper describes why the work was necessary, the means by which it was done, the difficulties encountered and overcome and the progress made to date.