# DART software - Copyright UCAR. This open source software is provided
# by UCAR, "as is", without charge, subject to all terms of use at
# http://www.image.ucar.edu/DAReS/DART/DART_download
#
# DART $Id$

The core algorithms of DART work with many different models
which have a variety of coordinate systems.  This directory
provides code for creating, setting/getting, copying location
information (coordinates) independently of the actual specific
coordinate information.  It also contains distance routines
needed by the DART algorithms.

Each of the different location_mod.f90 files provides the same
set of interfaces and defines a 'module location_mod', so by
selecting the proper version in your path_names_xxx file you
can compile your model code with the main DART routines.

threed_sphere:

The most frequently used version for real-world 3d models is
the 'threed_sphere' module, which uses latitude and longitude
coordinates, plus a vertical coordinate which can be meters,
pressure, or model level.

oned:

For small models, the 'oned' version is most frequently used.
It has a cyclic domain from 0 to 1.

threed_cartesian:

A full 3D X,Y,Z coordinate system.

others:

For other uses, there are also:
 'column', no x,y but 1d height, pressure, or model level for vertical.
 'annulus', a hollow 3d cylinder with azimuth, radius, and depth.
 'twod', a periodic 2d domain with x,y coordinates between 0 and 1.
 'twod_sphere', a 2d shell with latitude, longitude pairs.
 'threed', a periodic 3d domain with x,y,z coordinates between 0 and 1.
 'channel', a 3d domain periodic in x, limited in y, and unlimited z.

Other schemes can be added, as needed by the models.
Possible ideas are a non-periodic version of the 1d, 2d
cartesian versions.  Email 'dart@ucar.edu' if you have a different 
coordinate scheme which we might want to support.

testing:

The testall.csh script will cd into each of the locations
module directories and build and run a simple testcase to
verify the distance calculations and the read/write options
are working.  

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