Buffer (Analysis)

Summary

Creates buffer polygons around input features to a specified distance.

Learn more about how Buffer works

Illustration

Usage

• If buffering a projected feature class that has features covering a large region, or you are using a very large buffer distance, distortions in the projection can cause inaccurate buffers to be produced. You can completely avoid distortion when buffering by using a feature class that has a geographic coordinate system and specifying a Buffer Distance in linear units (meters, feet, and so forth, as opposed to angular units such as degrees). When this combination of inputs is used, the tool will generate true geodesic buffers that accurately represent distances on Earth's surface. Geodesic buffers may appear unusual on a flat map, but when displayed on a globe these buffers will look correct (you can use the ArcGlobe or ArcGIS Explorer applications to view geographic data on a three-dimensional globe). For more information, see How Buffer works.

  Note:

  You can change the coordinate system of a feature class using the Project tool, or you can set the Output Coordinate System geoprocessing environment before executing the Buffer tool, and this coordinate system will be used in creating buffers.

• Improve the accuracy of buffers created with projected inputs by using a projection that minimizes distance distortion, such as an Equidistant Conic or an Azimuthal Equidistant projection, and is geographically appropriate for your input.

• When buffering features in a projected coordinate system with output to a geodatabase feature class, the geometries created will often contain circular arc segments, especially when buffering points. If these buffers that contain circular arcs are re-projected to a different coordinate system, the location and size of the original buffers will be transformed, but the shape of the buffers will not change, causing the re-projected buffers to no longer accurately represent the area covered by the original buffer. If you wish to re-project buffers containing circular arcs, first use the Densify tool to convert circular arc segments to straight lines, then re-project the buffers.

• The output feature class will have a field, BUFF_DIST, that contains the buffer distance used to buffer each feature, in the linear unit of the input features' coordinate system. If a Dissolve Type of ALL or LIST is used, the output will not have this field.

• When buffering polygon features, negative buffer distances can be used to create buffers inside the polygon features. Using a negative buffer distance will reduce the polygons' boundaries by the distance specified.

  Caution:

  If the negative buffer distance is large enough to collapse the polygon to nothing, a null geometry will be generated. A warning message will be given, and any null geometry features will not be written to the output feature class.

• If a field from the Input Features is used to obtain buffer distances, the field's values can be either a number (5) or a number with a valid linear unit (5 Kilometers). If a field value is simply a number, it is assumed that the distance is in the linear unit of the Input Features' spatial reference (unless the Input Features are in a geographic coordinate system, in which case, the value is assumed to be in meters). If the linear unit specified in the field values is invalid or not recognized, the linear unit of the input features' spatial reference will be used by default.

  

• The Dissolve Field(s) parameter Add Field button is used only in ModelBuilder. In ModelBuilder, where the preceding tool has not been run or its derived data does not exist, the Dissolve Field(s) parameter may not be populated with field names. The Add Field button allows expected fields to be added to the Dissolve Field(s) list in order to complete the Buffer tool dialog box.

License:

Side Type (line_side) options LEFT, RIGHT, and OUTSIDE_ONLY and the End Type (line_end_type) option FLAT are only available with an Advanced license.

Syntax

Buffer_analysis (in_features, out_feature_class, buffer_distance_or_field, {line_side}, {line_end_type}, {dissolve_option}, {dissolve_field})

Parameter	Explanation	Data Type
in_features	The input point, line, or polygon features to be buffered.	Feature Layer
out_feature_class	The feature class containing the output buffers.	Feature Class
buffer_distance_or_field	The distance around the input features that will be buffered. Distances can be provided as either a value representing a linear distance or as a field from the input features that contains the distance to buffer each feature. If linear units are not specified or are entered as Unknown, the linear unit of the input features' spatial reference is used. When specifying a distance in scripting, if the desired linear unit has two words, like Decimal Degrees, combine the two words into one (for example, '20 DecimalDegrees').	Linear unit ;Field
line_side (Optional)	The side(s) of the input features that will be buffered. FULL —For line input features, buffers will be generated on both sides of the line. For polygon input features, buffers will be generated around the polygon and will contain and overlap the area of the input features. For point input features, buffers will be generated around the point. This is the default. LEFT —For line input features, buffers will be generated on the topological left of the line. This option is not valid for polygon input features. RIGHT —For line input features, buffers will be generated on the topological right of the line. This option is not valid for polygon input features. OUTSIDE_ONLY —For polygon input features, buffers will be generated only outside the input polygon (the area inside the input polygon will be erased from the output buffer). This option is not valid for line input features. License: This optional parameter is not available with a Basic or Standard license.	String
line_end_type (Optional)	The shape of the buffer at the end of line input features. This parameter is not valid for polygon input features. ROUND —The ends of the buffer will be round, in the shape of a half circle. This is the default. FLAT —The ends of the buffer will be flat, or squared, and will end at the endpoint of the input line feature. License: This optional parameter is not available with a Basic or Standard license.	String
dissolve_option (Optional)	Specifies the dissolve to be performed to remove buffer overlap. NONE —An individual buffer for each feature is maintained, regardless of overlap. This is the default. ALL —All buffers are dissolved together into a single feature, removing any overlap. LIST —Any buffers sharing attribute values in the listed fields (carried over from the input features) are dissolved.	String
dissolve_field [dissolve_field,...] (Optional)	The list of field(s) from the input features on which to dissolve the output buffers. Any buffers sharing attribute values in the listed fields (carried over from the input features) are dissolved.	Field

Code Sample

Buffer example (Python window)

The following Python window script demonstrates how to use the Buffer tool.

import arcpy
arcpy.env.workspace = "C:/data"
arcpy.Buffer_analysis("roads", "C:/output/majorrdsBuffered", "100 Feet", "FULL", "ROUND", "LIST", "Distance")

Buffer example (stand-alone script)

Find areas of suitable vegetation that exclude areas heavily impacted by major roads:

# Name: Buffer.py
# Description: Find areas of suitable vegetation which exclude areas heavily impacted by major roads

# import system modules 
import arcpy
from arcpy import env

# Set environment settings
env.workspace = "C:/data/Habitat_Analysis.gdb"

# Select suitable vegetation patches from all vegetation
veg = "vegtype"
suitableVeg = "C:/output/Output.gdb/suitable_vegetation"
whereClause = "HABITAT = 1" 
arcpy.Select_analysis(veg, suitableVeg, whereClause)

# Buffer areas of impact around major roads
roads = "majorrds"
roadsBuffer = "C:/output/Output.gdb/buffer_output"
distanceField = "Distance"
sideType = "FULL"
endType = "ROUND"
dissolveType = "LIST"
dissolveField = "Distance"
arcpy.Buffer_analysis(roads, roadsBuffer, distanceField, sideType, endType, dissolveType, dissolveField)

# Erase areas of impact around major roads from the suitable vegetation patches
eraseOutput = "C:/output/Output.gdb/suitable_vegetation_minus_roads"
xyTol = "1 Meters"
arcpy.Erase_analysis(suitableVeg, roadsBuffer, eraseOutput, xyTol)

Environments

Default Output Z Value, M Resolution, M Tolerance, Output M Domain, Output XY Domain, Output Z Domain, Output Coordinate System, Extent, Current Workspace, Geographic Transformations, Scratch Workspace, Output has M values, Output has Z values, Output Spatial Grid 1, Output Spatial Grid 2, Output Spatial Grid 3, XY Resolution, XY Tolerance, Z Resolution, Z Tolerance

Licensing Information

ArcGIS for Desktop Basic: Limited

ArcGIS for Desktop Standard: Limited

ArcGIS for Desktop Advanced: Yes