Package org.orekit.models.earth.ionosphere

Class GlobalIonosphereMapModel

  • All Implemented Interfaces:
    IonosphericModel, ParameterDriversProvider
    public class GlobalIonosphereMapModel
extends Object
implements IonosphericModel
    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 stream contains, for a given day, the values of the TEC for each hour of the day. Values are given on a global 2.5° x 5.0° (latitude x longitude) grid.

    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 The 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
    ...
    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​(SpacecraftState state,
                        TopocentricFrame baseFrame,
                        double frequency,
                        double[] parameters)
        Description copied from interface: IonosphericModel
        Calculates the ionospheric path delay for the signal path from a ground station to a 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.

        Specified by:
        pathDelay in interface IonosphericModel
        Parameters:
        state - spacecraft state
        baseFrame - base frame associated with the station
        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​(FieldSpacecraftState<T> state,
                                                       TopocentricFrame baseFrame,
                                                       double frequency,
                                                       T[] parameters)
        Description copied from interface: IonosphericModel
        Calculates the ionospheric path delay for the signal path from a ground station to a 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.

        Specified by:
        pathDelay in interface IonosphericModel
        Type Parameters:
        T - type of the elements
        Parameters:
        state - spacecraft state
        baseFrame - base frame associated with the station
        frequency - frequency of the signal in Hz
        parameters - ionospheric model parameters at state date
        Returns:
        the path delay due to the ionosphere in m