Topic:
How is grid rotation defined?

Description:
How to define a grids rotation and how these can be useful.       

Solution:
Grid rotation is measured as positive in an anticlockwise direction from the
east axis. Columns extend, depending on the rotation, approximately north/south
and rows are in the orthogonal direction.  For example, suppose you create a
grid and specify a row spacing of 1000, column spacing of 2500 and a rotation of
20 degrees. The resultant grid has a wider spacing in the x direction than in
the y direction and is orientated ENE-WSW. The nodes might be distributed
something like this when posted in basemap:


                                         x
                               x
                     x
           x                                x
                                 x
                       x
              x


Such a grid is useful to model a feature that is striking ENE, where most of
the seismic lines are dip lines, with the occasional, widely-spaced strike line.
This would have the affect of looking further in the strike direction than in
the dip direction for control points when gridding. 
How far it looks is controlled by the parameter "Grid Coverage".

See also: grid coverage 



Last Modified on: 14-SEP-00