/* Copyright 2002-2017 CS Systèmes d'Information
* Licensed to CS Systèmes d'Information (CS) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* CS licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/**
*
* This package provides classes to handle frames and transforms between them.
*
* <p>
* The {@link org.orekit.frames.Transform} class represents a full transform:
* combined rotation and translation, and their first time derivatives to handle kinematics.
* </p>
*
* <p>
* Each {@link org.orekit.frames.Frame} is defined by a transform linking it to
* another one, called its parent frame. The only exception is the root frame which has
* no parent. This implies that all frames are naturally organized as a tree with a single
* root. The predefined GCRF inertial frame was arbitrary chosen as the root for every tree.
* </p>
*
* <p>
* The {@link org.orekit.frames.FramesFactory} class implements several predefined reference
* frames. One set correspond to the frames from the various IERS conventions (ITRF and others).
* Other frames not belonging to the previous set are the EME2000 frame that was used prior
* to GCRF and which is linked to GCRF by a simple bias rotation, the MOD (Mean Of Date) frame
* which involves the IAU 1976 precession model, the TOD (True Of Date) frame which involves
* the IAU 1980 nutation model, the GTOD (Greenwich True Of Date) which involves the IAU 1982
* Greenwich sidereal time model and the Veis 1950 frame which involves a Veis modified sidereal
* time model.
* </p>
*
* <p>
* Some other frames are predefined outside of this package, in the {@link
* org.orekit.bodies.CelestialBodyFactory} class. They correspond to the Sun, Moon, planets, solar
* system barycenter and Earth-Moon barycenter. For convenience, the very important solar system
* barycenter frame, which is the ICRF, can also be retrieved from the factory in this package
* even if it is really implemented in the bodies package.
* </p>
*
* <p>
* The frames can be time dependent (for example the ITRF frame depends on time due to
* precession/nutation, Earth rotation and pole motion). In order to get a transform from one
* frame to another one, the date must be specified, and {@link
* org.orekit.frames.TransformProvider#getTransform(AbsoluteDate)} is called under the hood.
* If a user wants to implement his own date synchronized frame, he has to implement his
* own {@link org.orekit.frames.TransformProvider} class and provide it to the frame constructor.
* </p>
*
* @author Luc Maisonobe
* @author Fabien Maussion
* @author Véronique Pommier-Maurussane
* @author Pascal Parraud
*
*/
package org.orekit.frames;