Slope

Overview

Calculates surface slope from an input DEM and outputs a slope raster in the specified unit.

Slope describes how steeply surface elevation changes. It is commonly calculated from the first-order derivatives of the DEM in the x and y directions. A typical expression is $\theta = \arctan\left(\sqrt{(\partial z/\partial x)^2 + (\partial z/\partial y)^2}\right)$, which can then be converted to degrees, radians, or percent as needed.

Use Cases

• Basic preprocessing before terrain analysis such as slope orientation, solar radiation, and flow direction studies.
• Surface morphology studies such as landslide susceptibility, ecological suitability, and geomorphic zoning.
• Terrain factor input for hydrology analysis, soil erosion analysis, and engineering site selection.

Parameters

Parameter	Description	Notes
Input DEM raster file	Input digital elevation model (DEM) raster file.	Required
Z-axis scale factor	Multiplier applied to elevation values before calculation.	Required; default: 1.0
Slope unit	Unit used for the slope result.	Required; default: degrees; options: degrees (degrees), radians (radians), percent (percentage), rise/run (riserun)
Output slope raster file	Output raster file containing the slope result.	Required

Steps

1. Start the tool: Open the Geoprocessing Toolbox, go to Thematic Analysis > Terrain Analysis, and start the Slope tool.
2. Prepare the input: Select the Input DEM raster file and confirm that the input data is complete and readable.
3. Set core parameters: Configure Z-axis scale factor and Slope unit according to the analysis objective.
4. Set the output: Specify the Output slope raster file and confirm that the output path, format, and naming rules meet later workflow requirements.
5. Run and inspect results: Click Run to execute the task. After it completes, check whether the result range, value distribution, and spatial location are as expected.

Notes

• When multiple rasters are used together, first confirm that their coordinate systems, resolutions, extents, and grid alignment are consistent.
• Voids, noise, and abnormal elevation values in the DEM directly affect terrain factors such as slope, aspect, and curvature.
• If the elevation unit differs from the horizontal unit, use the Z-axis scale factor to correct the vertical-to-horizontal ratio.