WMMTinySwift

A Swift wrapper for the original WMM_Tiny library.

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Features

• Calculate magnetic variation (declination) for any location, altitude, and date.
• Lightweight and easy to use.
• Uses the latest World Magnetic Model (WMM 2025).

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Usage

let wmm = WMMTiny.shared
let magVar = wmm.magneticVariation(
    coordinate: CLLocationCoordinate2D(
        latitude: 37.7749,
        longitude: -122.4194
    ),
    altitudeKm: 10,
    date: Date()
)

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Implementation Notes

This package uses wmm.c and wmm.h from the original WMM_Tiny, with a slight modification to include altitude as an input parameter:

// include altitude above ellipsoid
r += height_km;
d += height_km;

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Regenerating WMM_COF.c

To re-generate the WMM_COF.c file from a WMM.COF model file, run:

swift run WWMConverter WMM.COF

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License

See MIT License for details.