.. auto-generated by dev_tools.docs.nxdl from the NXDL source contributed_definitions/NXcoordinate_system_set.nxdl.xml -- DO NOT EDIT

.. index::
    ! NXcoordinate_system_set (base class)
    ! coordinate_system_set (base class)
    see: coordinate_system_set (base class); NXcoordinate_system_set

.. _NXcoordinate_system_set:

=======================
NXcoordinate_system_set
=======================

..
    Contributors List

    .. |contrib_name| replace:: Rubel|RubelMozumder|https://avatars.githubusercontent.com/u/32923026?v=4|2023-06-14

    .. |contrib_name| replace:: Kuehbachm|mkuehbach|https://avatars.githubusercontent.com/u/14091504?v=4|2022-09-13

**Status**:

  base class, extends :ref:`NXobject`

**Description**:

  .. collapse:: Container to hold different coordinate systems conventions. ...

      Container to hold different coordinate systems conventions.

      It is the purpose of this base class to define these conventions and
      offer a place to store mappings between different coordinate systems
      which are relevant for the interpretation of the data described
      by the application definition and base class instances.

      For each Cartesian coordinate system users should use a set of
      NXtransformations:

      * These should define the three base vectors.  
      * The location of the origin.  
      * The affine transformations which bring each axis of this coordinate system  
        into registration with the McStas coordinate system.  
      * Equally, affine transformations should be given for the inverse mapping.

      As an example one may take an experiment or computer simulation where
      there is a laboratory (lab) coordinate system, a sample/specimen coordinate
      system, a crystal coordinate system, and additional coordinate systems,
      which are eventually attached to components of the instrument.

      If no additional transformation is specified in this group or if an
      instance of an NXcoordinate_system_set is absent it should be assumed
      the so-called McStas coordinate system is used.

      Many application definitions in NeXus refer to this `McStas <https://mailman2.mcstas.org/pipermail/mcstas-users/2021q2/001431.html>`_ coordinate system.
      This is a Cartesian coordinate system whose z axis points along the neutron 
      propagation axis. The systems y axis is vertical up, while the x axis points
      left when looking along the z-axis. Thus, McStas is a right-handed coordinate system.

      Within each NXtransformations a depends_on section is required. The depends_on
      field specifies if the coordinate system is the root/reference
      (which is indicated by writing "." in the depends_on section.)

**Symbols**:

  No symbol table

**Groups cited**:
  :ref:`NXtransformations`

.. index:: NXtransformations (base class); used in base class

**Structure**:

  .. _/NXcoordinate_system_set/TRANSFORMATIONS-group:

  **TRANSFORMATIONS**: (optional) :ref:`NXtransformations` 

    .. collapse:: A group of transformations which specify: ...

        A group of transformations which specify:

        * Three base vectors of the coordinate system.  
        * Origin of the coordinate system.  
        * A depends_on keyword. Its value can be "." or the name of an  
          NXtransformations instance which needs to exist in the  
          NXcoordinate_system_set instance.  
        * If the coordinate system is the reference one it has to be named  
          reference.

        In case of having more than one NXtransformations there has to be for  
        each additional coordinate system, i.e. the one not the reference:

        * A set of translations and rotations which map each base vector to the reference.  
        * A set of translations and rotations which map each reference base vector  
          to the coordinate system.

        The NXtransformations for these mappings need to be formatted
        according to the descriptions in NXtransformations.


Hypertext Anchors
-----------------

List of hypertext anchors for all groups, fields,
attributes, and links defined in this class.


* :ref:`/NXcoordinate_system_set/TRANSFORMATIONS-group </NXcoordinate_system_set/TRANSFORMATIONS-group>`

**NXDL Source**:
  https://github.com/nexusformat/definitions/blob/main/contributed_definitions/NXcoordinate_system_set.nxdl.xml