Nautical Almanac goes metric

Press, Volume CXI, Issue 32677, 5 August 1971, Page 17

Nautical Almanac goes metric

Boat owners already are confronted with the need to think no longer in fathoms and feet, but in metres and millimetres. The New Zealand Nautical Almanac and Tide Tables for 1972, now available, give all tides in metres, and new charts give depths of water and heights of land in metric measure.

In these two fields at least, the nautical world will , be officially metric from the be* ginning of next year, says the Metric Advisory Board. “These changes, which follow hot on the heels of the Celsius temperature scale, are in line with an interna-

, tional agreement to discon- ! tinue using fathoms and feet * on charts and in tide tables. : British Admiralty tide tables for 1972, for example, make ■ use of metres, and it is logical ! for, New Zealand to follow J suit,” the board reports.

CONVERSION CARD “The New Zealand tide tables for 1972 have all heights of tides in metres to one decimal place; thus a tide which this year is shown to have a height of 10ft,, will from next year have a height of 3.3 m. .The tables include a card for converting metres into feet or fathoms, but this will no longer be included in the years ahead when those who sail in small boats, pleasure craft and so on, are fully familiar with the new systenj.” - The board says that it will be many years before • all charts can be reprinted. This will pose a problem for boat owners using older charts, who will have to convert eitheir tide heights into feet or change the charted depths into metres in order to combine the two measurements to determine the total depth of water at a given place. . Echo-sounding devices showing the actual depth of water under the keel in fathoms and feet will have to be rescaled in metres.