Pitney Bowes MapInfo Vertical Mapper - Manual (Page 115)

Chapter 6: Working with Grids
User Guide
113
1 + 2 + 1 + 4 + (5.6) + 3 + 7 + 0 + 9
---------------------------------------------
8 + 6
Check the Fill Null Cells check box to have the Smoother compute the average for grid cells that
contain no data. You can clear this check box to ignore cells that do not contain data (though this
may retain some ‘noise’ in your output contour data).
Consider the example above with the exception of a null central cell value (‘V’, meaning ‘void’ or ‘no
data’):
1 + 2 + 1 + 4 + (V.6) + 3 + 7 + 0 + 9
---------------------------------------------
8 + 6
If you choose to fill null cells, then the central cell (V) will have a new value in the output grid. If you
choose not to fill null cells, then the central cell will remain empty (null) in the output grid.
Note The Smoother can significantly reduce the time it takes to complete the contouring process.
Use a small matrix size (3x3 or 5x5) and check the Fill Null Cells check box prior to
contouring your data.
Contouring with Grids
Vertical Mapper provides tools to convert grids to attribute-coded vector files using processes that
thread isolines, or contours, through the grid network (as in the next figure). Contour lines are paths
of constant values. Vertical Mapper computes contour lines as separate polylines or closed complex
regions where holes or islands have been “knocked-out”. This is important in the GIS environment
because the contour regions can immediately be used for analysis.
Lines are threaded through grid cells at defined values.