SnapPour

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

Usage tips

Map Algebra

The SnapPour function is used to ensure selection of points of high accumulated flow when delineating drainage basins using the Watershed function. SnapPour will search within snap_distance around the specified pour points for the cell of highest accumulated flow and move the pour point to that location.

The output of SnapPour is an integer raster.

Learn more about how to specify the input raster dataset in the Map Algebra expression of Raster Calculator.

Map Algebra syntax

SnapPour(<source_grid | point_file>, <acc_grid>, {snap_distance})

Parameter	Explanation
<source_grid \| point_file>	The source of pour points to be snapped. source_grid — A raster of cells to be used as pour points. All cells that are not NoData will be considered pour points and will be snapped point_file — An ASCII text file of x,y pairs specifying the location of cells to be snapped.
<acc_grid>	A raster of accumulated flow created with the FlowAccumulation function.
{snap_distance}	The maximum distance in map units to search for a cell of higher accumulated flow. The default snap distance is zero, the same as if SnapPour was not used.

Parameter

Explanation

<source_grid | point_file>

The source of pour points to be snapped.

source_grid — A raster of cells to be used as pour points. All cells that are not NoData will be considered pour points and will be snapped

point_file — An ASCII text file of x,y pairs specifying the location of cells to be snapped.

<acc_grid>

A raster of accumulated flow created with the FlowAccumulation function.

{snap_distance}

The maximum distance in map units to search for a cell of higher accumulated flow. The default snap distance is zero, the same as if SnapPour was not used.

Map Algebra example

snappour(sourcegrid, accumgrid)			
snappour(sourcegrid, accumgrid, 20)

SnapPour

Usage tips

Syntax

Map Algebra syntax

Map Algebra example

ArcObjects syntax

See Also