Package org.orekit.frames

Class Frame

  • All Implemented Interfaces:
    Serializable
    Direct Known Subclasses:
    CcsdsModifiedFrame, FactoryManagedFrame, L1Frame, L2Frame, LocalOrbitalFrame, TopocentricFrame, UpdatableFrame, VersionedITRF
    public class Frame
extends Object
implements Serializable
    Tridimensional references frames class.

    Frame Presentation

    This class is the base class for all frames in OREKIT. The frames are linked together in a tree with some specific frame chosen as the root of the tree. Each frame is defined by transforms combining any number of translations and rotations from a reference frame which is its parent frame in the tree structure.

    When we say a transform t is from frameA to frameB, we mean that if the coordinates of some absolute vector (say the direction of a distant star for example) has coordinates uA in frameA and uB in frameB, then uB=t.transformVector(uA).

    The transforms may be constant or varying, depending on the implementation of the transform provider used to define the frame. For simple fixed transforms, using FixedTransformProvider is sufficient. For varying transforms (time-dependent or telemetry-based for example), it may be useful to define specific implementations of transform provider.

    Author:
    Guylaine Prat, Luc Maisonobe, Pascal Parraud
    See Also:
    Serialized Form

    • Constructor Detail

      • Frame

        public Frame​(Frame parent,
             Transform transform,
             String name,
             boolean pseudoInertial)
      throws IllegalArgumentException
        Build a frame from its transform with respect to its parent.

        The convention for the transform is that it is from parent frame to instance. This means that the two following frames are similar:

         Frame frame1 = new Frame(FramesFactory.getGCRF(), new Transform(t1, t2));
 Frame frame2 = new Frame(new Frame(FramesFactory.getGCRF(), t1), t2);
        Parameters:
        parent - parent frame (must be non-null)
        transform - transform from parent frame to instance
        name - name of the frame
        pseudoInertial - true if frame is considered pseudo-inertial (i.e. suitable for propagating orbit)
        Throws:
        IllegalArgumentException - if the parent frame is null

      • Frame

        public Frame​(Frame parent,
             TransformProvider transformProvider,
             String name,
             boolean pseudoInertial)
      throws IllegalArgumentException
        Build a frame from its transform with respect to its parent.

        The convention for the transform is that it is from parent frame to instance. This means that the two following frames are similar:

         Frame frame1 = new Frame(FramesFactory.getGCRF(), new Transform(t1, t2));
 Frame frame2 = new Frame(new Frame(FramesFactory.getGCRF(), t1), t2);
        Parameters:
        parent - parent frame (must be non-null)
        transformProvider - provider for transform from parent frame to instance
        name - name of the frame
        pseudoInertial - true if frame is considered pseudo-inertial (i.e. suitable for propagating orbit)
        Throws:
        IllegalArgumentException - if the parent frame is null

    • Method Detail

      • getName

        public String getName()
        Get the name.
        Returns:
        the name

      • isPseudoInertial

        public boolean isPseudoInertial()
        Check if the frame is pseudo-inertial.

        Pseudo-inertial frames are frames that do have a linear motion and either do not rotate or rotate at a very low rate resulting in neglectible inertial forces. This means they are suitable for orbit definition and propagation using Newtonian mechanics. Frames that are not pseudo-inertial are not suitable for orbit definition and propagation.

        Returns:
        true if frame is pseudo-inertial

      • toString

        public String toString()
        New definition of the java.util toString() method.
        Overrides:
        toString in class Object
        Returns:
        the name

      • getParent

        public Frame getParent()
        Get the parent frame.
        Returns:
        parent frame

      • getDepth

        public int getDepth()
        Get the depth of the frame.

        The depth of a frame is the number of parents frame between it and the frames tree root. It is 0 for the root frame, and the depth of a frame is the depth of its parent frame plus one.

        Returns:
        depth of the frame

      • getAncestor

        public Frame getAncestor​(int n)
                  throws IllegalArgumentException
        Get the nth ancestor of the frame.
        Parameters:
        n - index of the ancestor (0 is the instance, 1 is its parent, 2 is the parent of its parent...)
        Returns:
        nth ancestor of the frame (must be between 0 and the depth of the frame)
        Throws:
        IllegalArgumentException - if n is larger than the depth of the instance

      • getTransformTo

        public Transform getTransformTo​(Frame destination,
                                AbsoluteDate date)
        Get the transform from the instance to another frame.
        Parameters:
        destination - destination frame to which we want to transform vectors
        date - the date (can be null if it is sure than no date dependent frame is used)
        Returns:
        transform from the instance to the destination frame

      • getTransformTo

        public <T extends org.hipparchus.RealFieldElement<T>> FieldTransform<T> getTransformTo​(Frame destination,
                                                                                       FieldAbsoluteDate<T> date)
        Get the transform from the instance to another frame.
        Type Parameters:
        T - the type of the field elements
        Parameters:
        destination - destination frame to which we want to transform vectors
        date - the date (can be null if it is sure than no date dependent frame is used)
        Returns:
        transform from the instance to the destination frame

      • getTransformProvider

        public TransformProvider getTransformProvider()
        Get the provider for transform from parent frame to instance.
        Returns:
        provider for transform from parent frame to instance

      • isChildOf

        public boolean isChildOf​(Frame potentialAncestor)
        Determine if a Frame is a child of another one.
        Parameters:
        potentialAncestor - supposed ancestor frame
        Returns:
        true if the potentialAncestor belongs to the path from instance to the root frame, excluding itself

      • getRoot

        protected static Frame getRoot()
        Get the unique root frame.
        Returns:
        the unique instance of the root frame

      • getFrozenFrame

        public Frame getFrozenFrame​(Frame reference,
                            AbsoluteDate freezingDate,
                            String frozenName)
        Get a new version of the instance, frozen with respect to a reference frame.

        Freezing a frame consist in computing its position and orientation with respect to another frame at some freezing date and fixing them so they do not depend on time anymore. This means the frozen frame is fixed with respect to the reference frame.

        One typical use of this method is to compute an inertial launch reference frame by freezing a topocentric frame at launch date with respect to an inertial frame. Another use is to freeze an equinox-related celestial frame at a reference epoch date.

        Only the frame returned by this method is frozen, the instance by itself is not affected by calling this method and still moves freely.

        Parameters:
        reference - frame with respect to which the instance will be frozen
        freezingDate - freezing date
        frozenName - name of the frozen frame
        Returns:
        a frozen version of the instance