Steps in “Point-in-Polygon” Analysis for MapInfo

By Melissa Landon, Red hen Systems, Inc.

• Open the “psuedo grid” table generated in MapCalc
• Open the “point features” table into the same Map Window
• Under the Table Menu, select the Update Column command
• The Update Column dialog box appears
• In the Table to Update field, select the name of the “point features” table
• In the Get Value From Table field, select the name of the “psuedo grid” table
• After changing the name of the Get Value From Table field, the Column to Update field will automatically change to Add New Temporary Column**
• Click on the Join button to the right of the Get Value From Table field
• The Specify Join dialog box appears
• Select the radio button next to the Where Object From Table “psuedo grid”
• In the drop down menu below this option, select the “contains” object from table “point features”
• Click the OK button to return to the Update Column dialog box
• In the Calculate field, select Value
• In the Of field, select KentTTime
• Activate the Browse Results option by placing a checkmark in the box to the left
• Click the OK button
• The “point features” table Browser will appear on top on the Map Window
• The “point features” table now contains a column at the end of the table titled KentTTime
• This new column contains the travel time associated with the grid cell in which the point feature resides
• If you choose to retain the new column of data in the “point features” table, select the Save Copy As command under the File Menu and save the updated table to a new file name

**If you want the new updated column to be retained as part of the “point features” table via the Save Table command without having to save the table to a new name, then you must first modify the structure of the “point features” table to contain an appropriate column labeled and formatted to accept the updated values from the “pseudo grid” table before executing the Update Column command. In this case you would select the new column name from the drop down list for the Column to Update field in the Update Column dialog box.