Summary
In ArcGIS Pro, the average or mean slope angle of an area can be calculated from the area’s contour lines. This can be used for studying the topography of a landscape, such as a valley or mountain range. Follow the workflow below to calculate the average slope of an area using contour lines in ArcGIS Pro.
Procedure
Note:
This workflow requires the Spatial Analyst license. Refer to ArcGIS Pro: Enable the Spatial Analyst extension for more information.
- Open the ArcGIS Pro project.
- On the ribbon, click Analysis > Tools to open the Geoprocessing pane.
- Use the Topo to Raster tool to create a surface raster layer from the contour lines.
- In the Geoprocessing pane, search for and select Topo to Raster (Spatial Analyst Tools).
- In the Topo to Raster pane, click the Parameters tab.
- Under Input feature data, select the contour lines layer for Feature layer,
- Select the contour value field of the data for Field, and Contour for Type.
- Specify a name for Output surface raster, and click Run.
The image below shows a surface raster layer of the area created from the contour lines. In this example, the TopoToRasterOut layer is created.
- Use the Int tool to convert the surface raster cells into integers.
- In the Geoprocessing pane, search for and select Int (Spatial Analyst Tools).
- In the Int pane, click the Parameters tab.
- Select the output layer from Step 3 for Input raster or constant value. In this example, the TopoToRasterOut layer is selected.
- Specify a name for Output raster, and click Run.
The image below shows the input raster cells converted into integers in a new feature layer. In this example, the IntOutput layer is created.
- Use the Slope tool to calculate the slopes of the surface raster area.
- In the Geoprocessing pane, search for and select Slope (Spatial Analyst Tools).
- In the Slope pane, click the Parameters tab.
- Select the output layer from Step 3 for Input raster. In this example, the TopoToRasterOut layer is selected.
- Specify a name for Output raster, and click Run.
The image below shows a new raster layer with the slopes of the area. In this example, the SlopeOutput layer is created.
- Use the Zonal Statistics tool to calculate the mean slope.
- In the Geoprocessing pane, search for and select Zonal Statistics (Spatial Analyst Tools).
- In the Zonal Statistics pane, click the Parameters tab.
- Select the output from Step 4 for Input Raster or Feature Zone Data. In this example, the IntOutput layer is selected.
- Select the output layer from Step 5 for Input Value Raster. In this example, the SlopeOutput layer is selected.
- Specify a name for Output Raster.
- Ensure Mean is selected for Statistics Type, and click Run.
The image below shows a new feature layer with the slope summary. In this example, the ZonalOutput layer is created.
- In the Contents pane, right-click the output layer from Step 6 and click Symbology.
- In the Symbology pane, click the Statistics tab. The average slope angle is displayed in the Mean statistics. In this example, the average slope angle is 24.5 degrees.