Window a Grid

Use the Grid and Image > Utilities > Window a Grid menu option (GRIDWIND GX) to window a subset grid from a larger grid (up to 16,000 x 16,000). The sub-area may be referenced in grid indices or in reference system units.

Window a Grid dialog options

Input grid file	File Name of the Input Grid(.grd file) Script Parameter: GRIDWIND.GRD
Output grid file	File Name of the Output Grid created from a mask in the input grid (.grd file) Script Parameter: GRIDWIND.NEW
Coordinates in GRID or GROUND units	Use "GRID" indices or "GROUND" units (Default is GRID). In "GRID" indices, the grid origin is at (1, 1). Script Parameter: GRIDWIND.COORD
Mask limits: X MIN	Minimum in X direction (Default is the minimum X in the original grid). Output grid limits are clipped to the original grid Script Parameter: GRIDWIND.XMIN
X MAX	Maximum in X direction (Default is the maximum X in the original grid). Output grid limits are clipped to the original grid Script Parameter: GRIDWIND.XMAX
Y MIN	Minimum in Y direction (Default is the minimum Y in the original grid). Output grid limits are clipped to the original grid limits. Script Parameter: GRIDWIND.YMIN
Y MAX	Maximum in Y direction (Default is the maximum Y in the original grid). Output grid limits are clipped to the original grid limits. Script Parameter: GRIDWIND.YMAX
Data limits: Z MIN	Z Data Limits – minimum (by default no minimum is applied). Script Parameter: GRIDWIND.ZMIN
Z MAX	Z Data Limits – maximum (by default no maximum is applied). Script Parameter: GRIDWIND.ZMAX
Out-of-range Z data is:	Z Data out-of-range is "CLIPPED" or "DUMMIED" (Default is DUMMIED). Script Parameter: GRIDWIND.CLIP
New grid cell size	New grid cell size. (If left blank, then the original grid cell sizes in X and Y is preserved. Script Parameter: GRIDWIND.CSIZE
Decimation factor	Decimation Factor (Default is 1). Script Parameter: GRIDWIND.DEC

Application Notes

If a parameter is left blank then its corresponding DEFAULT value is used.

The GRIDWIND GX will always start the output (windowed) grid at the point specified by the user (either by manual or interactive mode) and regrid using that point as the bottom left corner. If you want the windowed grid to start at the corner of a grid cell in the parent grid, you must specify the coordinates in Grid units and specify the window size in number of cells.

Windowing using GROUND Units

Unless the output cell size is specified, the output grid from GRIDWIND will maintain the original X and Y cell sizes. If the output cell size is specified, then the alignment of the output grid is fixed so that the grid cell locations are at integral multiples of the cell sizes. If the output cell size is not specified, then the output grid point locations will not be shifted; in other words, they shall remain at locations which are integral multiples of the cell size from the original grid origin location.

Windowing using GRID Units

The input grid window values are rounded down to the nearest integer. The output windowed grid origin is then always at the location given by the original grid origin, plus the input value, minus one, times the grid cell size. For instance, if 2.0 (two) is entered for X MIN, the grid origin is 50 and the cell size is 10, then the windowed grid will begin at 50 + (2-1)*10 = 60.

The output grid always has a square grid cell. If you specify an element separation value, input grids with rectangular grid cells will be re-interpolated to have square grid cell. If you wish to regrid to a different cell size and a smoother interpolation is desired, use BIGRID to re-grid the grid selecting one of BIGRID splining options.

Inside Data Margin (IDM)

If you want the mask a grid so that it will display in a map within the precise rectangular area defined, the inside data margin must be set to 0.0. The New Map menu commands have an entry for the inside data margin which has a default values of 1.0 cm.