wrldmagm

Use World Magnetic Model

    Note:   The '2000' or '2005' epoch year are outdated. For model years between 2000 and the start of 2010, use igrf11magm. For model years between 2010 and the start of 2015, use wrldmagm.

Syntax

[xyz, h, dec, dip, f] = wrldmagm(height, lat, lon, dyear)
[xyz, h, dec, dip, f] = wrldmagm(height, lat, lon, dyear, '2010')
[xyz, h, dec, dip, f] = wrldmagm(height, lat, lon, dyear, '2005')
[xyz, h, dec, dip, f] = wrldmagm(height, lat, lon, dyear, '2000')

Description

[xyz, h, dec, dip, f] = wrldmagm(height, lat, lon, dyear) calculates the Earth's magnetic field at a specific location and time using the World Magnetic Model (WMM). The default WMM is WMM-2010, which is valid from January 1, 2010, until December 31, 2014.

Inputs required by wrldmagm are:

heightA scalar value, in meters
latA scalar geodetic latitude, in degrees, where north latitude is positive, and south latitude is negative
lonA scalar geodetic longitude, in degrees, where east longitude is positive, and west longitude is negative
dyearA scalar decimal year. Decimal year is the desired year in a decimal format to include any fraction of the year that has already passed.

Outputs calculated for the Earth's magnetic field include:

xyzMagnetic field vector in nanotesla (nT)
hHorizontal intensity in nanotesla (nT)
decDeclination in degrees
dipInclination in degrees
fTotal intensity in nanotesla (nT)

[xyz, h, dec, dip, f] = wrldmagm(height, lat, lon, dyear, '2010') is an alternate method for calling WMM-2010, or 2010 epoch.

[xyz, h, dec, dip, f] = wrldmagm(height, lat, lon, dyear, '2005') is an alternate method for calling WMM-2005, or 2005 epoch.

[xyz, h, dec, dip, f] = wrldmagm(height, lat, lon, dyear, '2000') is the method for calling WMM-2000, or 2000 epoch.

Examples

Calculate the magnetic model 1000 meters over Natick, Massachusetts on July 4, 2010, using WMM-2010:

[XYZ, H, DEC, DIP, F] = wrldmagm(1000, 42.283, -71.35, decyear(2010,7,4),'2010')
XYZ =

  1.0e+004 *

    1.9229
   -0.5139
    4.8865

H =

  1.9904e+004

DEC =

  -14.9627

DIP =

   67.8376

F =

  5.2763e+004

Assumptions and Limitations

The WMM specification produces data that is reliable five years after the epoch of the model, which begins January 1 of the model year selected. The WMM specification describes only the long-wavelength spatial magnetic fluctuations due to the Earth's core. Intermediate and short-wavelength fluctuations, contributed from the crustal field (the mantle and crust), are not included. Also, the substantial fluctuations of the geomagnetic field, which occur constantly during magnetic storms and almost constantly in the disturbance field (auroral zones), are not included.

References

http://www.ngdc.noaa.gov/geomag/WMM/DoDWMM.shtml

"NOAA Technical Report: The US/UK World Magnetic Model for 2005–2010"

See Also

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