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Buffer

This tool allows you to create zones around points, lines, or polygons with a specified distance.

1. Explanation​

A buffer is a tool used to delineate the catchment area around a specific point, line, or polygon illustrating the extent of influence or reach from that feature. Users can define the distance of the buffer, thereby customizing the radius of the area covered.

Buffer Types

2. Example use cases​

  • Analyze population within 500m of train stations
  • Count shops accessible within 1000m of bus stops

3. How to use the tool?​

1
Click on Tools Options.
2
Under the Geoprocessing menu, click on Buffer.

Input​

3
Select the Input layer around whose features you want to create the buffers. Point, line and polygon layers can be used.

Configuration​

The Configuration section becomes available as soon as an input layer is selected.

4

Choose the Distance Source:

  • Constant (default): the same distances are used for all features. Enter them in Buffer Distances, separated by commas (e.g. 100, 200, 300). GOAT creates one buffer per feature and per distance.
  • Field: every feature gets its own distance. Select the numeric Distance Field of the input layer that contains the distance. Features with an empty value or a value of 0 are skipped.
5
Select the Distance Units of the distances: Meters (default), Kilometers, Feet, Miles, Nautical Miles or Yards.
6

Configure Merge overlapping buffers:

  • Disabled (default): GOAT creates a separate buffer around each input feature. The buffers keep the attributes of their input feature.
  • Enabled: GOAT merges all buffers of the same distance into one polygon. The result contains one polygon per distance; the attributes of the input features are not kept. This is useful if you want to see the total area covered at each distance.
7
If you enabled Merge overlapping buffers, the Polygon Difference switch appears. When you enable it, GOAT subtracts each smaller distance from the next larger one, so the result consists of rings that do not overlap. This only has an effect with the Constant distance source and at least two buffer distances.
Buffers without merging, merged, and merged with polygon difference

8

Optionally, click the options icon Options in the Configuration header to show further settings for the buffer shape:

  • Curve Smoothness: number of segments used to approximate a quarter circle (default 8). Higher values give smoother edges but take longer to calculate.
  • Cap Style: shape of the buffer at the ends of lines: CAP ROUND (default), CAP FLAT or CAP SQUARE.
  • Join Style: shape of the buffer at corners: JOIN ROUND (default), JOIN MITRE or JOIN BEVEL.
  • Mitre Limit: only shown for JOIN MITRE; limits how far pointed corners extend (default 1).

Results​

9
Optionally, change the Result layer name (default: Buffer).
10
Click on Run. This starts the calculation of the buffer. As soon as it is finished, the resulting polygon layer is added to your map.

The result layer contains the column buffer_distance. With the Constant distance source, it holds the distance in meters, and the buffers are colored by distance. With the Field distance source, it holds the value of the distance field.

Tip

Want to style your buffers and create nice-looking maps? See Styling.