# Slope (Spatial Analyst)

## Summary

Identifies the slope (gradient, or rate of maximum change in z-value) from each cell of a raster surface.

## Illustration

 OutRas = Slope(InRas1)

## Usage

• 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 values in the output depends on the type of measurement units.

• For degrees, the range of slope values is 0 to 90.
• For percent rise, the range is 0 to essentially 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. See how Slope works for a more detailed explanation of the range of output values with this option.

• 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.

## Syntax

Slope (in_raster, {output_measurement}, {z_factor})
 Parameter Explanation Data Type in_raster The input surface raster. Raster Layer output_measurement(Optional) Determines the measurement units (degrees or percentages) of the output slope data. DEGREE — The inclination of slope will be calculated in degrees. PERCENT_RISE — Keyword to output the percent rise, also referred to as the percent slope. String z_factor(Optional) Number of ground x,y units in one surface z unit. The z-factor adjusts the units of measure for the z units when they are different from the x,y units of the input surface. The z-values of the input surface are multiplied by the z-factor when calculating the final output surface. If the x,y units and z units are in the same units of measure, the z-factor is 1. This is the default. If the x,y units and z units are in different units of measure, the z-factor must be set to the appropriate factor, or the results will be incorrect. For example, if your z units are feet and your x,y units are meters, you would use a z-factor of 0.3048 to convert your z units from feet to meters (1 foot = 0.3048 meter). Double

#### Return Value

 Name Explanation Data Type out_raster The output slope raster. Raster

## Code Sample

Slope example 1 (Python window)

This example determines the slope values of the input surface raster.

```import arcpy
from arcpy import env
from arcpy.sa import *
env.workspace = "C:/sapyexamples/data"
outSlope = Slope("elevation", "DEGREE", 0.3043)
outSlope.save("C:/sapyexamples/output/outslope01")```
Slope example 2 (stand-alone script)

This example determines the slope values of the input surface raster.

```# Name: _Ex_02.py
# Description: Identifies the rate of maximum change
#    in z-value from each cell.
# 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"
outMeasurement = "DEGREE"
zFactor = 0.3043

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

# Execute Slope
outSlope = Slope(inRaster, outMeasurement, zFactor)

# Save the output
outSlope.save("C:/sapyexamples/output/outslope02")```

## Licensing Information

ArcView: Requires Spatial Analyst or 3D Analyst
ArcEditor: Requires Spatial Analyst or 3D Analyst
ArcInfo: Requires Spatial Analyst or 3D Analyst

6/29/2011