Pitney Bowes MapInfo Vertical Mapper - Manual (Page 179)

Chapter 10: Aggregating Data
User Guide
177
• Median Value: The median value is the middle value of all points within the “same point”
distance of the aggregated coordinate. If there are an even number of points, the median value is
the average of the two middle values.
• Average of Min & Max Values: This value is determined by averaging the minimum and
maximum values of all points within the “same point” distance of the aggregated coordinate.
• Sum of Values: The sum of values is determined by summing all values of valid points within the
“same point” distance of the aggregated coordinate.
The Coincident Point Distance box—enables you to define the minimum distance between two
points before they are considered coincident.
The default value is 10 percent of the mean distance between the data points and is measured in
coordinate system units. Choose a small or zero distance to treat points in the data set that are very
closely spaced or overlie each other. As the distance setting becomes greater, there will be more
coincident points, and consequently the number of points in the output data set will decrease.
Point Aggregation with Statistics
The point aggregation with statistics techniques provide information about the mathematical and
spatial characteristics of the aggregation process. To quantitatively measure the aggregation
process, Vertical Mapper offers three techniques: Forward Stepping, Cluster Density, and Square
Cell. These methods are grouped under the category Point Aggregation With Statistics.
1. From the Vertical Mapper menu, choose the Data Aggregation > Point Aggregation With
Statistics command.
2. From the Select Table to Aggregate list in the Select Table and Column dialog box, choose a
point table from the list of open MapInfo tables.
3. From the Select Column list, choose a column of data to transfer to the new aggregated file.
4. Enable the Ignore Records Containing Zero check box to include only non-zero records, and
click the Next button.
5. To aggregate coincident points, clear the No Coincident Point Handling check box in the
Select Coincident Point Technique dialog box.
6. Choose an averaging technique option, and click the Next button.
7. In the Aggregation Technique section of the Select Aggregation Technique and Statistics dialog
box, choose an aggregation technique.
8. In the Aggregate Point Attributes section, enable any of the check boxes.
9. In the Aggregation Distance box, type the desired distance.
10. Enable the Create Regions Table check box if you want to build a MapInfo table of regions, and
the STD Ellipse Table check box if you want to build a table of standard deviation ellipses.
11. In the File Name box, type a new file name or accept the default.
12. Click the Finish button.
Once the process is complete, a dialog box appears stating the extent of the aggregation as shown
below. The aggregated point file appears in a new Map window with a default symbol style applied to
each point. If you choose the Create Regions Table option, the aggregation regions table appears in
a separate Map window and is assigned the suffix “AggRegion”.