Creating a buffer

Creating a buffer

The buffer function creates a buffer zone around a spatial object such as a point, line or a boundary.

Buffers are useful whether you want to analyze data within a certain distance from an object. A circle is a kind of buffer around a point, so the Buffer function is more often used with lines or boundaries. E.g. How many households are within 1km from a railway line.

To create a buffer around a boundary

• Open a map

• Add the required boundary to the map

• Within the Map Properties tab, select the layer and click Edit…

• Click on the Select… button next to Geometry Expression

• Delete the current expression from the Expression box at the top of the window

• In the Expression box at the top of the window type:

• BUFFER(MASTER.BOUNDARY,1,1,2) – If a boundary

• BUFFER(MASTER.LINE,500,2,1) – If a line

Where

• Distance = The distance you want the buffer to extend to

• Units = The units of the distance; 1=Kilometers 2=Meters 3=Miles

• Buffer Type = 1=Corridor Zone 2=Enclosing Area

Select OK, and then click Create

Note: In the above image, to demonstrate the buffer, we added the original boundary on top (the darker area). In your system, you will only see the new buffer area.