What are buffers in GIS?
Definition of buffer in GIS
A buffer in GIS is a reclassification based on distance: classification of within/without a given proximity.
Buffers and GIS data types
Buffering involves measuring the distance outward in all directions from an object. Buffering can be done on all three types of vector data: point, line, area. The resulting buffer is a polygon file.
Uniform buffer
Most often buffers are measured in uniform distance. For example, creating a 50′ buffer around all rivers or a 100 meter buffer around the points of all cities.
Variable buffer
A buffer based on different distances is called a variable buffer.
For example, the noise level surrounding surround a street network may be based on the traffic load. Therefore a variable buffer may be used to illustrate the noise level by using a larger distance for high traffic roads and a shorter distance for quieter roads.
In this map below, the cities in Oklahoma have different sized buffers depending on the elevation of that city. The city of Guymon in the northwestern section of Oklahoma has the highest elevation at 952 meters (3,154 feet) and therefore has the largest buffer area.
Buffer direction in GIS for polygons
Bidirectional buffers in GIS
For polygons that are buffered, there are two additional types of buffers: bi-directional (or bidirectional) and setbacks.
Bidirectional buffers are polygons that are buffered from the boundary outwards as well as inwards.
Setback buffers in GIS
Setback buffers are polygons that are only buffered from the boundary inward.
An example of using setbacks is seen with property lines. Setbacks can be used to buffer the distance from a property line to show how far away from the property line a building has to be.
In GIS you can also buffer a buffer, this is called a doughnut buffer if around a point object initially.
How Big Should a Buffer Be?
The distance a buffer should be around a GIS feature is dependent upon the need.
- Arbitrary Buffers – Gut feelings
- Causative Buffers – A priori knowledge
- Measurable Buffer – E.g. measured value such as a viewshed
- Mandated Buffers – Predefined values (1000′ ordinance around schools)
Buffering with ArcGIS Pro
This helpful video from Rick Duchscher shows how to use the buffer tool in ArcGIS Pro:
Buffering Tool for ArcMap
If you want to create a zone of equidistance around a geographic feature you will need to understand buffering. Buffering is an important tool for determining the area covered within a specific location. For example, you may buffer school locations to visualize the areas that are within 1000′ feet of a school.
The video below shows how to use the Analysis Tools (part of the Toolbox section) to create a buffer in ArcMap
The video is 1:36 minutes long.
Buffering in QGIS
The Q-tips channel has a two-part video series on how to use buffering in QGIS. Part one:
This article was originally written on June 20, 2013 and has since been updated.
