Package org.orekit.models.earth

Class GeoMagneticField

java.lang.Object
org.orekit.models.earth.GeoMagneticField
public class GeoMagneticField extends Object
Used to calculate the geomagnetic field at a given geodetic point on earth. The calculation is estimated using spherical harmonic expansion of the geomagnetic potential with coefficients provided by an actual geomagnetic field model (e.g. IGRF, WMM).

Based on original software written by Manoj Nair from the National Geophysical Data Center, NOAA, as part of the WMM 2010 software release (WMM_SubLibrary.c)

Author:
Thomas Neidhart
See Also:

  • Constructor Summary

    Constructors
    Modifier
    Constructor
    Description
    protected
    GeoMagneticField(String modelName, double epoch, int maxN, int maxNSec, double validityStart, double validityEnd)
    Create a new geomagnetic field model with the given parameters.

  • Method Summary

    Modifier and Type
    Method
    Description
    GeoMagneticElements
    calculateField(double latitude, double longitude, double height)
    Calculate the magnetic field at the specified geodetic point identified by latitude, longitude and altitude.
    static double
    getDecimalYear(int day, int month, int year)
    Utility function to get a decimal year for a given day.
    double
    getEpoch()
    Returns the epoch for this magnetic field model.
    String
    getModelName()
    Returns the model name.
    protected void
    setMainFieldCoefficients(int n, int m, double gnm, double hnm)
    Set the given main field coefficients.
    protected void
    setSecularVariationCoefficients(int n, int m, double dgnm, double dhnm)
    Set the given secular variation coefficients.
    boolean
    supportsTimeTransform()
    Indicates whether this model supports time transformation or not.
    GeoMagneticField
    transformModel(double year)
    Time transform the model coefficients from the base year of the model using secular variation coefficients.
    GeoMagneticField
    transformModel(GeoMagneticField otherModel, double year)
    Time transform the model coefficients from the base year of the model using a linear interpolation with a second model.
    double
    validFrom()
    Returns the start of the validity period for this model.
    double
    validTo()
    Returns the end of the validity period for this model.

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Constructor Details

    • GeoMagneticField

      protected GeoMagneticField(String modelName, double epoch, int maxN, int maxNSec, double validityStart, double validityEnd)
      Create a new geomagnetic field model with the given parameters. Internal structures are initialized according to the specified degrees of the main and secular variations.
      Parameters:
      modelName - the model name
      epoch - the epoch of the model
      maxN - the maximum degree of the main model
      maxNSec - the maximum degree of the secular variations
      validityStart - validity start of this model
      validityEnd - validity end of this model

  • Method Details

    • getEpoch

      public double getEpoch()
      Returns the epoch for this magnetic field model.
      Returns:
      the epoch

    • getModelName

      public String getModelName()
      Returns the model name.
      Returns:
      the model name

    • validFrom

      public double validFrom()
      Returns the start of the validity period for this model.
      Returns:
      the validity start as decimal year

    • validTo

      public double validTo()
      Returns the end of the validity period for this model.
      Returns:
      the validity end as decimal year

    • supportsTimeTransform

      public boolean supportsTimeTransform()
      Indicates whether this model supports time transformation or not.
      Returns:
      true if this model can be transformed within its validity period, false otherwise

    • setMainFieldCoefficients

      protected void setMainFieldCoefficients(int n, int m, double gnm, double hnm)
      Set the given main field coefficients.
      Parameters:
      n - the n index
      m - the m index
      gnm - the g coefficient at position n,m
      hnm - the h coefficient at position n,m

    • setSecularVariationCoefficients

      protected void setSecularVariationCoefficients(int n, int m, double dgnm, double dhnm)
      Set the given secular variation coefficients.
      Parameters:
      n - the n index
      m - the m index
      dgnm - the dg coefficient at position n,m
      dhnm - the dh coefficient at position n,m

    • calculateField

      public GeoMagneticElements calculateField(double latitude, double longitude, double height)
      Calculate the magnetic field at the specified geodetic point identified by latitude, longitude and altitude.
      Parameters:
      latitude - the WGS84 latitude in radians
      longitude - the WGS84 longitude in radians
      height - the height above the WGS84 ellipsoid in meters
      Returns:
      the GeoMagneticElements at the given geodetic point

    • transformModel

      public GeoMagneticField transformModel(double year)
      Time transform the model coefficients from the base year of the model using secular variation coefficients.
      Parameters:
      year - the year to which the model shall be transformed
      Returns:
      a time-transformed magnetic field model

    • transformModel

      public GeoMagneticField transformModel(GeoMagneticField otherModel, double year)
      Time transform the model coefficients from the base year of the model using a linear interpolation with a second model. The second model is required to have an adjacent validity period.
      Parameters:
      otherModel - the other magnetic field model
      year - the year to which the model shall be transformed
      Returns:
      a time-transformed magnetic field model

    • getDecimalYear

      public static double getDecimalYear(int day, int month, int year)
      Utility function to get a decimal year for a given day.
      Parameters:
      day - the day (1-31)
      month - the month (1-12)
      year - the year
      Returns:
      the decimal year represented by the given day