Pitney Bowes MapInfo Vertical Mapper - Manual (Page 46)

Rectangular Interpolation
44
Vertical Mapper 3.7
A radius is generated around each grid node from which the closest data point in each
quadrant is selected to be used in the calculation.
Exploring the Rectangular Interpolation Dialog Box
The Rectangular Interpolation dialog box enables you to specify parameters for the gridding
algorithm. Rectangular interpolation uses a bilinear method for estimating individual grid node
values. At each grid node, a circular search area of a set radius is generated and divided into
quadrants. Four data points from the original point file are selected, one from each quadrant where
each point is the nearest one to the node. A linear averaging solution is applied to the selected
points to solve for the grid node value.
The Cell Size box enables you to set the cell size in real units. The grid dimensions (in cell units)
vary inversely with cell size: the smaller the cell, the larger the grid file. The value you choose should
be a compromise between the degree of resolution required for analysis and visualization purposes
and the processing time and file size. The default value is calculated by dividing the diagonal extent
of the point file by 200, which is considered an optimum number based on the computing power
required to solve the rectangular algorithm.