- (nautical) A technique for navigation using planar geometry.
1735, Benjamen Martin, A New Compleat and Universal System or Body of Decimal Arithmetick, page 318:
- In Plain Sailing, or That by the Plain Chart, the Parts of a Triangle receive new Denominations.
- (nautical, proscribed) A technique for navigation using the assumption the Earth is flat.
The heart of the technique is finding the departure from the results obtained by assuming that the earth's surface is flat. This seems commonly forgotten and a definition often given is "navigation using the assumption that the earth's surface is flat". Justification can be found in The analectic magazine 1817.