The grid length is the distance in map units from the first grid line (grid origin) to the last grid line (opposite grid edge).
Enter the grid length value in the Length text box under Gridding Geometry in the Gridding dialog box. The X- and Y- length can be different. After you have made changes, click <Update Grid Map>.
With Auto On enabled, changing the grid length changes the grid spacing and number of grid lines in order to maintain the relationship: [lines-1]*[spacing] = grid length.
With Auto On disabled, the grid length can be changed independently of the grid spacing and grid lines.
If you only change the grid length, an error message will appear, warning you that you must also change the grid lines and/or grid spacing to maintain the relationship: [lines-1]*[spacing] = grid length.
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