# HydroGeoSphere/Defining a 2-D Mesh

The following instructions can be used to obtain 2-D slice data.

## Generate uniform rectangles

* xl, nbx Length and number of rectangles in the x-direction
* yl, nby Length and number of rectangles in the y-direction
Generates a 2-D grid for a rectangular domain made up of uniform rectangles. Each rectangular element will be assigned a default zone number of 1. It is identical to the generate uniform blocks instruction except that we drop the z-axis parameters.

## Generate variable rectangles

* nx Number of nodes in the x-direction
* xi(i),i=1,nx x-coordinates of the nx nodes.
* ny Number of nodes in the y-direction
* yi(i),i=1,ny y-coordinates of the ny nodes.
Generates a 2-D grid for a rectangular domain made up of variably-sized rectangles. Each rectangular element will be assigned a zone number of 1. It is almost identical to the generate variable blocks instruction except that we drop the z-axis parameters.

## Generate rectangles interactive

This instruction works in exactly the same way as the Generate blocks interactive instruction described in Section 5.3.2, except that input is limited to the x− and y-directions and a 2-D mesh of 4-node rectangular elements is generated.

## Read gms 2d grid

* gmsfile Name of the file which contains the 2-D slice data.
Reads a file which contains data defining a 2-D slice. The format of this file is described in detail in Section F.1 and is compatible with that produced by the Groundwater Modeling System (GMS) software which was developed at Brigham Young University for the US Department of Defense.

## Read gb 2d grid

* prefix Prefix of the GRID BUILDER files which contain the node coordinates, element incidences and element zone numbers for the 2-D triangular mesh. This is a string variable.
Reads the files which contain data defining a 2-D slice composed of 3-node triangular elements. These files are described in detail in Section G.1 and are compatible with output generated by the GRID BUILDER program.

## Read fractran 2d grid

* prefix Prefix of the FRACTRAN files which contain the node coordinates, element incidences and element zone numbers for the 2-D rectangular element mesh. This is a string variable.
Reads the files which contain data defining a 2-D slice composed of 4-node rectangular elements. These files are compatible with output generated by the FRACTRAN program.
For a 2-D slice made of 4-node rectangular elements, the following instructions can be used to remove elements:

## Remove rectangles with shapefile

* arcview_prefix Prefix of the ARCVIEW shape file.
* unproject_file If .TRUE, this logical switch causes grok to read grid unprojection data as described in Section 5.3.10 and to apply it to the data read from the ARCVIEW shapefile.
* project_file If .TRUE, this logical switch causes grok to read grid projection data as described in Section 5.3.10 and to apply it to the data read from the ARCVIEW shapefile.
* outside If .TRUE, elements located outside the area defined in the ARCVIEW shapefile are removed. If .FALSE, elements located inside the area are removed.

## Remove rectangles with blanking file

As above except a blanking file in surfer format is used instead of an ARCVIEW shape file.

## Raster to scl

* arcview_file_name Name of the Arcview ASCII file.
* bandwidth Cell bandwidth used for averaging.
Reads an ARCVIEW ascii file and interpolates a value for each 2-D mesh node. The results are written to a GMS formatted scalar file called output.scl.

## Raster to nprop

* arcview_file_name Name of the Arcview ASCII file.
* bandwidth Cell bandwidth used for averaging.
Reads an ARCVIEW ascii file and interpolates a value for each 2-D mesh node. The results are written to a Grid Builder compatible binary file called raster2nprop.output.nprop.

## Raster to element

* arcview_file_name Name of the Arcview ASCII file.
* Statistic Statistic to be used to interpolate values. Acceptable values for the variable statistic are:
          max count
          nearest
       If variable statistic is set to max count read the following:
          (a) bandwidth Cell bandwidth used for averaging.
Reads an ARCVIEW ascii file and interpolates a value for each 2-D mesh element. The results are written as a list of element number and value to a file called output.el.