Pitney Bowes MapInfo Vertical Mapper - Manual (Page 33)

Chapter 3: Creating Grids Using Interpolation
User Guide
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Note Use the Ruler in MapInfo Professional to examine your point data file and measure gaps in
the distribution of points over the map area. Use this information as a guideline in entering an
appropriate value for the maximum triangle side length.
The Coincident Point Distance box enables you to group or aggregate data points into a single
new point with a recalculated value. As the distance setting becomes greater, the number of points
aggregated correspondingly increases. This may be appropriate in dealing with highly variable and
irregularly distributed data. By increasing the coincident point distance, you prevent the creation of
very small or sliver triangles that result in artifacts in the output grid.
The Coincident Point Aggregation section enables you to define the mathematical expression for
handling aggregated data. For example, choosing a large coincident point distance and clicking the
Average Value option button will create a new set of data points for triangulation, spaced
approximately according to the distance setting and with recalculated values based on the average
of all points in each coincident point area. New points are placed at the geometric centre of the
original group.
The Save TRI File check box enables you to save the TIN surface for future gridding.
The TRI File name box enables you to enter a new file name for the .tri file.
The Extents button displays a summary of the geographic size and the z-value range of the original
point database, the density of the points, and the data value units.
Exploring the TIN Interpolation Dialog Box
The grid creation process consists of overlying a regularly-spaced network of equal-sized cells on
top of the triangulated (TIN) surface and then estimating a new value for each cell based on a
combination of variables. The variables include original point values, slope of individual and adjacent
TIN faces, and distance to neighbouring triangles. The end result is a smoothed surface that passes
through all of the original data points.
The TIN Interpolation dialog box enables you to set a number of user-defined parameters in the
algorithm that control the grid generation from the TIN surface.