Types of Buffers - MapInfo_Pro - 2023

MapInfo Pro supports the following buffer type:

• Convex hull buffers create a region object that represents a polygon based on the nodes from the input object. You can think of the convex hull polygon as an operator which places a rubber band around all of the points. It will consist of the minimum number of points so that all points lie on or inside the polygon. With convex hull buffers, no inside angle is greater than 180 degrees.

Convex Hull Buffers

The Convex Hull command provides another means of creating a polygon around a selected object or objects. Convex Hull is similar to creating a buffer in several ways. Like a buffer, the Convex Hull command always creates an object from the input objects, and it will place the result objects into the editable layer. In addition, you have a choice to create one convex hull object from all of the input objects, or to create one convex hull object for each input object.

The resulting region object(s) are based on the nodes from the input object. The Convex Hull command can be thought of as an operator that places a rubber band around all of the points. It consists of a minimal set of points such that all other points lie on or inside the polygon. Since the polygon is convex, no interior angles are greater than 180 degrees. No attribute data is aggregated in this operation. To use Convex Hull, a Map window must be active, it must have an editable layer, and objects in the editable layer must be selected.

To create convex hull objects:

1. On the SPATIAL tab, in the Edit group, click Convex Hull to open the Create Convex Hull dialog box.
2. Select the type of convex hull objects you want to create. You have two options:
   • One output object for all input objects button is the default setting. It creates one convex hull object around all of the selected objects.
   • One output object for each input object button creates a convex hull object around each selected object.
3. Click OK.

   Your map redisplays. The convex hull object(s) is displayed over the input objects. If you want to save this data, save the editable table. The convex hull object is selected when it displays.

4. To change the fill of the convex hull object, do one of the following:
   • Double-click it to open the Region Object dialog box. Click the Style icon at the bottom of the dialog box to open the Region Style dialog box. Make any changes you like and click OK.
   • Select the convex hull object, if it is not already. On the SPATIAL tab, in the Create group, on the Style list, click Region Style from the list to open the Region Style dialog box. Make the changes you want and click OK.