IGRF and NCEI World/Enhanced Magnetic Model Interface

wmm2020_extract(
  lon,
  lat,
  year = mm_decimal_year(Sys.Date()),
  height = mm_ellipsoidal_height(lon, lat, 0)
)

igrf13_extract(
  lon,
  lat,
  year = mm_decimal_year(Sys.Date()),
  height = mm_ellipsoidal_height(lon, lat, 0)
)

emm2017_extract(
  lon,
  lat,
  year = mm_decimal_year(Sys.Date()),
  height = mm_ellipsoidal_height(lon, lat, 0)
)

mm_ellipsoidal_height(lon, lat, height)

mm_decimal_year(date)

mm_version()

mm_egm9615_geoid_int

Arguments

lon, lat	Vectors of coordinates.
year	A decimal year (e.g., 2020.2120). The World Magnetic Model is valid between 2020.0 and 2025.0; the Enhanced Magnetic Model is valid between 2000.0 and 2022.0.
height	Height above the WGS84 ellipsoid in kilometers. Use `mm_ellipsoidal_height()` to convert geoid elevations (EGM9615) to ellipsoidal values.
date	An R date object or value that can be coerced to one.

Format

An object of class integer of length 1038961.

Value

A data frame with columns - decl: Magnetic variation in degrees - incl: Inclination of the magnetic field in degrees - decl_err, incl_err: Error associated with declination and inclination, respectively.

References

NCEI World Magnetic Model https://www.ngdc.noaa.gov/geomag/WMM/DoDWMM.shtml.

NCEI Enhanced Magnetic Model https://www.ngdc.noaa.gov/geomag/EMM/index.html.

IGRF-13 https://www.ngdc.noaa.gov/IAGA/vmod/home.html.

NCEI Geomagnetic Modeling Team and British Geological Survey. 2019. World Magnetic Model 2020. NOAA National Centers for Environmental Information. doi: 10.25921/11v3-da71 , 2020, accessed 2021-02-23.

Chulliat, A., W. Brown, P. Alken, C. Beggan, M. Nair, G. Cox, A. Woods, S. Macmillan, B. Meyer and M. Paniccia, The US/UK World Magnetic Model for 2020-2025: Technical Report, National Centers for Environmental Information, NOAA, doi: 10.25923/ytk1-yx35 , 2020.

Examples

wmm2020_extract(-64, 45, mm_decimal_year("2021-01-01"))
#>        decl     incl decl_err incl_err
#> 1 -16.89051 67.16415     0.21       90
emm2017_extract(-64, 45, mm_decimal_year("2021-01-01"))
#>        decl     incl decl_err incl_err
#> 1 -16.69539 66.89187       NA       NA
igrf13_extract(-64, 45, mm_decimal_year("2021-01-01"))
#>        decl     incl decl_err incl_err
#> 1 -16.88586 67.16703       NA       NA