Magnetic Declination and Bearing Conversion

Magnetic-to-true and true-to-magnetic with east-is-least / west-is-best memo.

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Formula and source

True bearing = magnetic bearing + east declination (or − west declination). 'East is least, west is best' memo. Declination from NOAA NCEI World Magnetic Model.

NOAA NCEI World Magnetic Model (WMM) 2025 by name; U.S. Army FM 3-25.26 by name.

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