Slope

Map Algebra:
OutRas = Slope(InRas1)

Command Line:
Slope_sa InRas1 OutRas

Usage tips

Command line and Scripting

• Slope is the rate of maximum change in z-value from each cell.

• The use of a z-factor is essential for correct slope calculations when the surface z units are expressed in units different from the ground x,y units.

• The range of slope values in degrees is 0 to 90. For percent rise, the range is 0 for near infinity. A flat surface is 0 percent, a 45 degree surface is 100 percent, and as the surface becomes more vertical, the percent rise becomes increasingly larger.

• If the center cell in the immediate neighborhood (3 x 3 window) is NoData, the output is NoData.

• If any neighborhood cells are NoData, they are assigned the value of the center cell; then the slope is computed.

• The following environment settings affect this tool:

  • General: Current Workspace, Scratch Workspace, Output Coordinate system, Output Extent, Snap Raster.
  • Raster Analysis: Cell size, Mask.
  • Raster Storage: See the Raster Storage settings for the particular output raster format selected.

Map Algebra

• The surface information for calculating the slope can be expressed as raster.item for any numeric item in the value attribute table. The default item is Value.

• The use of a z-factor is essential for correct slope calculations when the surface z units are expressed in units which are different from the ground x,y units.

• The range of slope values in degrees is 0 to 90. For percent rise, the range is 0 for near infinity. A flat surface is 0 percent, a 45 degree surface is 100 percent, and as the surface becomes more vertical, the percent rise becomes increasingly larger.

• If the center cell in the immediate neighborhood (3 x 3 window) is NoData, the output is NoData.

• If any neighborhood cells are NoData, they are assigned the value of the center cell; then the slope is computed.

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

ArcObjects

• Valid input for the geoDataset to ArcObjects is a Raster, RasterDataset, RasterBand, or RasterDescriptor.

• The use of a z-factor is essential for correct slope calculations when the surface z units are expressed in units different from the ground x,y units.

• The range of values with the Degree option of slopeType is 0 to 90. The range of the PercentRise option is 0 to near infinity. A flat surface is 0 percent, a 45 degree surface is 100 percent, and as the surface becomes more vertical, the percent rise becomes increasingly larger.

• If the center cell in the immediate neighborhood (3 x 3 window) is NoData, the output is NoData.

• If any neighborhood cells are NoData, they are assigned the value of the center cell; then the slope is computed.

• The output from the ArcObjects method is a raster object.

Command line syntax
An overview of the Command Line window
Slope_sa <in_raster> <out_raster> {DEGREE | PERCENT_RISE} {z_factor}

Command line example

Slope_sa C:/data/dem C:/data/slope PERCENT_RISE

Scripting syntax
About getting started with writing geoprocessing scripts
Slope_sa (in_raster, out_raster, output_measurement, z_factor)

Script example

# Slope_sample.py
# Description: 
#   Derives slope from a raster surface.
# Requirements: None
# Author: ESRI
# Date: Sept 6, 2005
# Import system modules
import arcgisscripting

# Create the Geoprocessor object
gp = arcgisscripting.create()

try:
    # Set local variables
    InRaster = "C:/data/dem"
    OutRaster = "C:/data/slope"
    InMeasurementType = "PERCENT_RISE"

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

    # Process: Slope
    gp.Slope_sa(InRaster, OutRaster, InMeasurementType)

except:
    # If an error occurred while running a tool, then print the messages.
    print gp.GetMessages()

Map Algebra syntax
Slope(<grid>, {DEGREE | PERCENTRISE})

Slope(<grid>, <z_factor>, {DEGREE | PERCENTRISE})

Map Algebra example

slope(ingrid)
slope(ingrid, percentrise)
slope(ingrid, .328)
slope(ingrid, degree, 2)

ArcObjects syntax
ISurfaceOp::Slope (geoDataset As IGeoDataset, slopeType As esriGeoAnalysisSlopeEnum, [zFactor As Variant]) As IGeoDataset

ArcObjects example

' Create the RasterSurfaceOp object
Dim pSurfaceOp As ISurfaceOp
Set pSurfaceOp = New RasterSurfaceOp

' Declare the input raster object
Dim pInputDataset As IGeoDataset

' Calls function to open a raster dataset from disk
Set pInputDataset = OpenRasterDataset ("D:\SpatialData", "inputdataset")

' Declare the output raster object
Dim pOutputRaster As IGeoDataset

' Calls the method
Set pOutputRaster = pSurfaceOp.Slope (pInputDataset, esriGeoAnalysisSlopeDegrees)