Pitney Bowes MapInfo Vertical Mapper - Manual (Page 114)

Smoothing a Grid
112
Vertical Mapper 3.7
A default output table file name will be provided in the Smoothed Grid Table field based on the
name of the selected input grid (“_Smooth” suffix is added). You may change this default file name
or click the Browse button to select an existing TAB file to overwrite with the new smoothed data.
You may want to use the default settings until you are comfortable with the way this utility works.
Use the Smoothing Window Size field to control the level of smoothness of the grid. This setting
tells the Smoother how big a matrix to look at when computing a grid cell’s average neighboring cell
value.
The default value is 3, which means a matrix of 3 by 3 cells. This smoothing window size number
must be an odd number and range from 3 to 21 (for example, 3, 5, 7, 9, 11, 13, 15, 17, 19 and 21).
The ‘smoothness’ of your contour will depend on how large a value you use; a value of 21 will
compute the average of a 21 by 21 matrix, thus yielding a smoother contour due to more grid data
used in the average computation for each grid cell. A value of 3 will compute the average of a 3 by 3
matrix, thus yielding a rougher contour due to less grid data used in the average computation for
each grid cell.
Use the Central Cell Weight field to set the weight of the central cell’s value when computing the
new averaged cell value. This gives the middle of the contour segment more weight in determining
the new path of the smoothed contour segment being defined by the grid.
For example, in the 3 by 3 matrix below,
1 2 1
4 5 3
7 0 9
If the central ‘5’ cell’s weight is set as 1, then the new central cell value is calculated as:
1 + 2 + 1 + 4 + (5.1) + 3 + 7 + 0 + 9
--------------------------------------------------
8 + 1
Where the value 8 in the denominator is the number of cells other than the central cell, and the value
1 both being added to the denominator and being multiplied by the central cell value in the
numerator is the central cell weight.
In order to give the central cell value a greater weight, you can enter a weight larger than 1. For
example, if you change the central cell weight in the matrix above to 6, the new computed value for
that cell is: