Vel2Grid - velocity model description to 3D model grid
======================================================

Given a velocity model description, **Vel2Grid** generates a 3D model
Grid header and buffer files containing velocities, slownesses or other
model specification.

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`Overview`_ - `Running the program-Input`_ - `Output`_ - `Processing and
Display of results`_ - `[NonLinLoc Home]`_

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Overview
--------

The Vel2Grid program converts analytic or other velocity model
specifications into a `3D Grid`_ file containing velocity or slowness
values.

The Vel2Grid program uses a "flat earth", rectangular, left-handed,
*x,y,z,t* coordinate system (positive X = East, positive Y = North,
positive Z = down). Distance units are kilometers.

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Running the program - Input
---------------------------

Synopsis: ``Vel2Grid InputControlFile``

The Vel2Grid program takes a single argument ``InputControlFile`` which
specifies the complete path and filename for an `Input Control File`_
with certain required and optional statements specifying program
parameters and input/output file names and locations. See the `Vel2Grid
Statements section`_ of the Input Control File for more details. Note
that to run Vel2Grid the `Generic Statements section`_ of the Input
Control File must contain the ``CONTROL`` and ``TRANS`` (Geographic
Transformation) statements.

In addition, the Vel2Grid program requires a set of `Vel2Grid
Statements`_ in the Input Control File that specify a layered model or a
3D velocity model. The velocity model can be specified in the control
file by:

A set of ```LAYER```_ statements defining a horizontally layered model
with constant or constant-gradient velocity and density in each layer.

A set of ```VERTEX```_, ```EDGE```_, and ```POLYGON2```_ statements
defining a 2D polygon model and a ```2DTO3DTRANS```_ statement to
convert this 2D model into a 3D model. Optionally, there may be a set of
LAYER<

.. _Overview: #_overview_
.. _Running the program-Input: #_running_
.. _Output: #_output_
.. _Processing and Display of results: #_processing_
.. _[NonLinLoc Home]: ./index.html
.. _3D Grid: ./formats.html#_grid_
.. _Input Control File: ./control.html
.. _Vel2Grid Statements section: ./control.html#_Vel2Grid_
.. _Generic Statements section: ./control.html#_generic_
.. _Vel2Grid Statements: ./control.html#_Vel2Grid_
.. _``LAYER``: ./control.html#_Vel2Grid_layer_
.. _``VERTEX``: ./control.html#_Vel2Grid_vertex_
.. _``EDGE``: ./control.html#_Vel2Grid_edge_
.. _``POLYGON2``: ./control.html#_Vel2Grid_polygon2_
.. _``2DTO3DTRANS``: ./control.html#_Vel2Grid_2d3dtrans_