10 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 eventu ally have to be replaced by a geocentric datum. The Canadian Hydrograp hic 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 framew ork stations became known on the North American Datum of 1983 (equival ent to the World Geodetic System of 1984), CHS started the conversion of Canadian charts to that datum. This paper describes why the work wa s necessary, the means by which it was done, the difficulties encounte red and overcome and the progress made to date.