Desktop Help 10.0 - Snap Pour Point (Spatial Analyst)

Summary

Snaps pour points to the cell of highest flow accumulation within a specified distance.

Usage

The Snap Pour Point tool is used to ensure the selection of points of high accumulated flow when delineating drainage basins using the Watershed tool. Snap Pour Point will search within a snap distance around the specified pour points for the cell of highest accumulated flow and move the pour point to that location.
If the input raster or feature pour point data is a point feature class, it will be converted to a raster internally for processing.
The output is an integer raster when the original pour point locations have been snapped to locations of higher accumulated flow.
When there is only one input pour point location, the extent of the output is that of the accumulation raster. If there is more than one pour point location, the extent of the output is determined by the settings in the Spatial Analyst analysis environment.

Syntax

SnapPourPoint (in_pour_point_data, in_accumulation_raster, snap_distance, {pour_point_field})

Parameter	Explanation	Data Type
in_pour_point_data	The input pour point locations that are to be snapped. For rasters, all cells that are not NoData (i.e., have a value) will be considered pour points and will be snapped. For point datasets, specifies the locations of cells that will be snapped.	Raster Layer
in_accumulation_raster	The input flow accumulation raster. This can be created with the Flow Accumulation tool.	Raster Layer
snap_distance	Maximum distance, in map units, to search for a cell of higher accumulated flow.	Double
pour_point_field (Optional)	Field used to assign values to the pour point locations. If the pour point dataset is a raster, use Value. If the pour point dataset is a feature, use a numeric field. If the field contains floating-point values, they will be truncated into integers.	Field

Return Value

Name	Explanation	Data Type
out_raster	The output pour point integer raster where the original pour point locations have been snapped to locations of higher accumulated flow.	Raster

Code Sample

SnapPourPoint example 1 (Python window)

This example snaps pour points to the cell of highest flow accumulation within a specified distance.

import arcpy
from arcpy import env
from arcpy.sa import *
env.workspace = "C:/sapyexamples/data"
outSnapPour = SnapPourPoint("pourpoint", "flowaccumulation.img", 5,"VALUE") 
outSnapPour.save("c:/sapyexamples/output/outsnpprpnt01")

SnapPourPoint example 2 (stand-alone script)

This example snaps pour points to the cell of highest flow accumulation within a specified distance.

# Name: SnapPourPoints_Ex_02.py
# Description: Snaps pour points to the cell of highest 
#              flow accumulation within a specified distance.
# 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
inPourPoint = "pourpoint"
inFlowAccum = "flowaccumulation.img"
tolerance = 5
pourField = "VALUE"

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

# Execute SnapPourPoints
outSnapPour = SnapPourPoint(inPourPoint, inFlowAccum, tolerance, 
                            pourField) 

# Save the output 
outSnapPour.save("c:/sapyexamples/output/outsnpprpnt02")

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

Snap Pour Point (Spatial Analyst)