Pitney Bowes MapInfo Vertical Mapper - Manual (Page 68)

Understanding the Trade Area Analysis Model
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Vertical Mapper 3.7
8. In the Data Description box, type an annotation (maximum 31 characters). This will be carried
as a header in the grid file.
9. Enable the Ignore Records Containing Zero check box if you want to include only non-zero
records.
10. Click the Next button and enter the required information in the dialog box.
11. Click the Finish button.
If you are running the Patronage Probability For One Site option of the trade area analysis
model, you are prompted to use the VM Picker Tool to select one site when you click the Finish
button.
Once the grid is created, it appears in a Map window with a default colour palette applied. You can
change the colour range assigned to the grid file. For more information, see
Using the Grid Colour
Tool for Numeric Grids on page 99 .
Exploring the Huff Model Dialog Box
The Huff Model dialog box summarizes information relating to the site table and enables you to set
parameters in the algorithm that control the creation of the trade area analysis grid. This dialog box
is used for calculating trade areas for single and multiple sites
Note If you are solving a data set that spans a large area or if the data is entered far from the
meridian or parallels of the projection, ensure the data set is in Latitude/Longitude
coordinates. If you are working at the city level, there will be minimal error in the distance
calculations if your data is in a projected map form and lies close to the central meridian or
standard parallels of the projection.
The Cell Size box enables you to define the cell size in the native coordinate system units of the
map. The grid dimension (in cell units) varies 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, the processing time, and file size. The grid dimensions (in cell width and
height) and the grid file size (in kilobytes) are displayed and updated as the cell size is adjusted.