Package org.orekit.models.earth.ionosphere

Class GlobalIonosphereMapModel

  • All Implemented Interfaces:
    IonosphericModel, ParameterDriversProvider
    public class GlobalIonosphereMapModel
extends AbstractIonosphericModel
    Global Ionosphere Map (GIM) model. The ionospheric delay is computed according to the formulas: 
               40.3
    δ =  --------  *  STEC      with, STEC = VTEC * F(elevation)
            f²
    With:
    • f: The frequency of the signal in Hz.
    • STEC: The Slant Total Electron Content in TECUnits.
    • VTEC: The Vertical Total Electron Content in TECUnits.
    • F(elevation): A mapping function which depends on satellite elevation.
    The VTEC is read from a IONEX file. A file contains, for a given day, VTEC maps corresponding to snapshots at some sampling hours within the day. VTEC maps are TEC Values on regular latitude, longitude grids (typically global 2.5° x 5.0° grids).

    A bilinear interpolation is performed the case of the user initialize the latitude and the longitude with values that are not contained in the stream.

    A temporal interpolation is also performed to compute the VTEC at the desired date.

    IONEX files are obtained from Crustal Dynamics Data Information System.

    The files have to be extracted to UTF-8 text files before being read by this loader.

    Example of file: 

          1.0            IONOSPHERE MAPS     GPS                 IONEX VERSION / TYPE
 BIMINX V5.3         AIUB                16-JAN-19 07:26     PGM / RUN BY / DATE
 BROADCAST IONOSPHERE MODEL FOR DAY 015, 2019                COMMENT
   2019     1    15     0     0     0                        EPOCH OF FIRST MAP
   2019     1    16     0     0     0                        EPOCH OF LAST MAP
   3600                                                      INTERVAL
     25                                                      # OF MAPS IN FILE
   NONE                                                      MAPPING FUNCTION
      0.0                                                    ELEVATION CUTOFF
                                                             OBSERVABLES USED
   6371.0                                                    BASE RADIUS
      2                                                      MAP DIMENSION
    350.0 350.0   0.0                                        HGT1 / HGT2 / DHGT
     87.5 -87.5  -2.5                                        LAT1 / LAT2 / DLAT
   -180.0 180.0   5.0                                        LON1 / LON2 / DLON
     -1                                                      EXPONENT
 TEC/RMS values in 0.1 TECU; 9999, if no value available     COMMENT
                                                             END OF HEADER
      1                                                      START OF TEC MAP
   2019     1    15     0     0     0                        EPOCH OF CURRENT MAP
     87.5-180.0 180.0   5.0 350.0                            LAT/LON1/LON2/DLON/H
    92   92   92   92   92   92   92   92   92   92   92   92   92   92   92   92
    92   92   92   92   92   92   92   92   92   92   92   92   92   92   92   92
    92   92   92   92   92   92   92   92   92   92   92   92   92   92   92   92
    92   92   92   92   92   92   92   92   92   92   92   92   92   92   92   92
    92   92   92   92   92   92   92   92   92
    ...

    Note that this model pathDelay methods requires the topocentric frame to lie on a OneAxisEllipsoid body shape, because the single layer on which pierce point is computed must be an ellipsoidal shape at some altitude.

    Author:
    Bryan Cazabonne
    See Also:
    "Schaer, S., W. Gurtner, and J. Feltens, 1998, IONEX: The IONosphere Map EXchange Format Version 1, February 25, 1998, Proceedings of the IGS AC Workshop Darmstadt, Germany, February 9–11, 1998"

    • Method Detail

      • pathDelay

        public double pathDelay​(Vector3D localP1,
                        Vector3D localP2,
                        TopocentricFrame baseFrame,
                        AbsoluteDate receptionDate,
                        double frequency,
                        double[] parameters)
        Description copied from interface: IonosphericModel
        Calculates the ionospheric path delay for the signal path from a ground station to an observing object (ground station or satellite).

        This method is intended to be used for orbit determination issues. In that respect, if the elevation is below 0° the path delay will be equal to zero.

        For individual use of the ionospheric model (i.e. not for orbit determination), another method signature can be implemented to compute the path delay for any elevation angle.

        Parameters:
        localP1 - position of path start point in baseFrame
        localP2 - position of path end point in baseFrame
        baseFrame - topocentric frame of point with lowest altitude between p1 and p2
        receptionDate - date at signal reception
        frequency - frequency of the signal in Hz
        parameters - ionospheric model parameters at state date
        Returns:
        the path delay due to the ionosphere in m

      • pathDelay

        public <T extends CalculusFieldElement<T>> T pathDelay​(FieldVector3D<T> localP1,
                                                       FieldVector3D<T> localP2,
                                                       TopocentricFrame baseFrame,
                                                       FieldAbsoluteDate<T> receptionDate,
                                                       double frequency,
                                                       T[] parameters)
        Description copied from interface: IonosphericModel
        Calculates the ionospheric path delay for the signal path from a ground station to an observing object (ground station or satellite).

        This method is intended to be used for orbit determination issues. In that respect, if the elevation is below 0° the path delay will be equal to zero.

        For individual use of the ionospheric model (i.e. not for orbit determination), another method signature can be implemented to compute the path delay for any elevation angle.

        Type Parameters:
        T - type of the elements
        Parameters:
        localP1 - position of path start point in baseFrame
        localP2 - position of path end point in baseFrame
        baseFrame - topocentric frame of point with lowest altitude between p1 and p2
        receptionDate - date at signal reception
        frequency - frequency of the signal in Hz
        parameters - ionospheric model parameters at state date
        Returns:
        the path delay due to the ionosphere in m