Extract by Circle (Spatial Analyst)

Summary

Extracts the cells of a raster based on a circle.

Usage

• The center of the cell is used to determine whether a cell is inside or outside a circle. If the center is within the arc of the circle, the cell is considered fully inside even if portions of the cell fall outside the circle.

• Cell locations that are not selected are assigned a value of NoData.

• When a multiband raster is specified as input, a new multiband raster will be created as output. Each individual band in the input multiband raster will be analyzed accordingly.

  The default output format is an ESRI grid stack. Note that the name of an ESRI grid stack cannot start with a number, use spaces, or be more than 9 characters in length.

• If the input is a layer created from a multiband raster with more than three bands, the extraction operation will only consider the bands that were loaded (symbolized) by the layer. As a result, the output multiband raster can only have three bands, corresponding to those used in the display of the input layer.

• If the input raster is integer, the output raster will be integer. If the input is floating point, the output will be floating point.

Syntax

ExtractByCircle (in_raster, center_point, radius, {extraction_area})

Parameter	Explanation	Data Type
in_raster	The input raster from which cells will be extracted.	Raster Layer
center_point	The Point class dictates the center coordinate (x,y) of the circle defining the area to be extracted. The form of the class is: Point (x, y) The coordinates are specified in the same map units as the input raster.	Point
radius	Radius of the circle defining the area to be extracted. The radius is specified in map units and is in the same units as the input raster.	Double
extraction_area (Optional)	Identifies whether to extract cells inside or outside the input circle. INSIDE — A keyword specifying that the cells inside the input circle should be selected and written to the output raster. All cells outside the circle will receive NoData values on the output raster. OUTSIDE — A keyword specifying that the cells outside the input circle should be selected and written to the output raster. All cells inside the circle will receive NoData values on the output raster.	String

Return Value

Name	Explanation	Data Type
out_raster	The output raster containing the cell values extracted from the input raster.	Raster

Code Sample

ExtractByCircle example 1 (Python window)

This example extracts cells within a 500-meter radius around a point location.

import arcpy
from arcpy import env
from arcpy.sa import *
env.workspace = "C:/sapyexamples/data"
outExtCircle = ExtractByCircle("elevation", arcpy.Point(482838.823, 222128.982),
                                500, "INSIDE")
outExtCircle.save("c:/sapyexamples/output/extcircle")

ExtractByCircle example 2 (stand-alone script)

This example extracts cells within a 1,000-meter radius around a point location.

# Name: ExtractByCircle_Ex_02.py
# Description: Extracts the cells of a raster based on a circle.
# Requirements: Spatial Analyst Extension
# Author: ESRI

# Import system modules
import arcpy
from arcpy import env
from arcpy.sa import *

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

# Set local variables
inRaster = ("elevation")
centerPoint = arcpy.Point(482838.823, 222128.982)
circRadius = 1000
extractType = "INSIDE"

# Check out the ArcGIS Spatial Analyst extension license
arcpy.CheckOutExtension("Spatial")

# Execute ExtractByCircle
outExtCircle = ExtractByCircle(inRaster, centerPoint, circRadius, 
                               extractType)

# Save the output 
outExtCircle.save("c:/sapyexamples/output/extcircle02")

Environments

Cell Size, Current Workspace, Mask, Output Coordinate System, Extent, Scratch Workspace, Snap Raster

Licensing Information

ArcView: Requires Spatial Analyst

ArcEditor: Requires Spatial Analyst

ArcInfo: Requires Spatial Analyst