# Create Grid System

Copyrights (c) 2007 by Volker Wichmann
This module creates a new user specified Grid System for use with other modules.
First of all, please consider the following issues before using the module:
(a) all calculations of the module refer to the lower left corner of the grid system, i.e. the xMin and yMin values. This coordinate is fixed unless you specify an offset.
(b) the module follows the philosophy of SAGA in that the values describing the extent refer to the cell centers. If you like to match the extent with the border of a grid, use an offset.
The module provides four possibilities to set/determine the extent of the grid system:
(1) by specifying the coordinate of the lower left cell (xMin, yMin) and the number of cells in W-E (NX) and S-N (NY) direction
(2) by specifying the coordinates the of lower left (xMin, yMin) and the upper right (xMax, yMax) cell
(3) by the extent of the shape(s) provided in the Data Objects section
(4) by the extent of the grid(s) provided in the Data Objects section
After selecting the appropriate method to determine the extent, the next step is to specify the cellsize of the new grid system.
For all methods supplied to determine the extent but number (1), three possibilities are provided to adjust cellsize and grid system extent (please remember, the lower left corner is fixed!):
(I) adjust the extent to match the cellsize
(II) adjust the cellsize to match the extent in E-W direction
(III) adjust the cellsize to match the extent in S-N direction
Finally it is possible to apply an offset to the lower left corner of the grid system. In this case check the Use Offset option and specify the offset in W-E and S-N direction. Positive values result in a shift in E/N, negative in W/S direction.
In order to create the grid system the module needs to create a dummy grid.

## Parameters

Dummy Grid
Output Data Object
Set extent by
Choice
  Please choose a method of module operation.
  Available choices: xMin, yMin, NX, NY, xMin, yMin, xMax, yMax, Shape(s), Grid(s)
xMin
Floating point
  minimum x value
yMin
Floating point
  minimum y value
xMax
Floating point
  maximum x value
yMax
Floating point
  maximum y value
NX
Integer
  number of cells in W-E direction
  Minimum: 1.0
NY
Integer
  number of cells in S-N direction
  Minimum: 1.0
Cellsize
Floating point
  Cellsize
Adjust
Choice
  Choose method how to adjust input values.
  Available choices: Extent to CellSize, CellSize to W-E Extent, CellSize to S-N Extent
Use Offset
Boolean
  Apply offset?
X offset
Floating point
  Positive values result in a shift in E direction.
Y offset
Floating point
  Positive values result in a shift in N direction.
Initialization Value
Floating point
  Value which is assigned to the dummy grid.
Shape(s)
Input Shapes list
  Shape(s) to fit extent to
Grid(s)
Input Grid list
  Grid(s) to fit extent to