A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: David C
Date: 2020 Jan 7, 19:08 -0800
I have always known the difference between magnetic and true north as variation as in
Variation east magnetic least.
Variation west magnetic best.
However the GPS Test Plus app calls it declination.
The Admiralty Manual of Navigation 1928 calls it variation.
Bowditch 1958 calls it variation (so it is not a UK vs US thing) and notes that it is called declination by magneticians (interesting word!).
Bowditch 1943 states that it is sometimes called declination by surveyors. A surveying text book I have confirms the use of declination.
The Dictionary of Nautical Terms and Terms (CWT Layton 1967) states that variation was the former name for variation of compass.
The point of all this? When I started typing I was planning to get grumpy at the app's incorrect use of "declination". However I have decided that the use is legitimate. Maybe the app author has a surveying background or consulted surveying text books? I think that I should stop worrying and make better use of my time!!!