Desktop Help 10.0 - Extract by Points (Spatial Analyst)

Summary

Extracts the cells of a raster based on a set of coordinate points.

Usage

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

ExtractByPoints (in_raster, points, {extraction_area})

Parameter	Explanation	Data Type
in_raster	The input raster from which cells will be extracted.	Raster Layer
points [point,...]	A Python list of Point class objects denote the locations where values will be extracted from the raster. The point objects are specified in a list of x,y coordinate pairs. The form of the object is: [point(x₁,y₁), point(x₂,y₂),...] The points are in the same map units as in_raster.	Point
extraction_area (Optional)	Identifies whether to extract cells based on the specified point locations (inside) or outside the point locations (outside) . INSIDE — A keyword specifying that the cell in which the selected point falls will be written to the output raster. All cells outside the box will receive NoData on the output raster. OUTSIDE — A keyword specifying that the cells outside the input points should be selected and written to 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

ExtractByPoints example 1 (Python window)

This example extracts cells from a raster based on the specified point coordinates.

import arcpy
from arcpy import env
from arcpy.sa import *
env.workspace = "C:/sapyexamples/data"
pointList = [arcpy.Point(743050, 4321275), arcpy.Point(743100, 4321200),
             arcpy.Point(734500,4322000)]
outPointExtract = ExtractByPoints("soil", pointList,"INSIDE")
outPointExtract.save("c:/sapyexamples/output/pntextract")

ExtractByPoints example 2 (stand-alone script)

This example extracts cells from a raster based on the specified point coordinates.

# Name: ExtractByPoints_Ex_02.py
# Description: Extracts the cells of a raster based on a set of points.
# 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 = "soil"
pointList = [arcpy.Point(743050, 4321275), 
             arcpy.Point(743100, 4321200), 
             arcpy.Point(743500, 4322000),
             arcpy.Point(742900, 4321800)]

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

# Execute ExtractByPoints
outPointExtract = ExtractByPoints("soil", pointList,"INSIDE")

# Save the output 
outPointExtract.save("c:/sapyexamples/output/pntext")

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

6/29/2011

Extract by Points (Spatial Analyst)