Aspect
Overview
Calculates the downslope direction from elevation changes in an input DEM and outputs an aspect raster.
Aspect represents the direction of maximum downslope change on a surface. It is usually expressed clockwise from north, with north as 0 degrees and values ranging from 0 to 360 degrees. The calculation estimates the terrain gradient from elevation differences in the DEM neighborhood, then converts the gradient direction to an azimuth.
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 |
| Output aspect raster file | Output aspect raster file. | Required |
Steps
- Start the tool: Open the Geoprocessing Toolbox, go to Thematic Analysis > Terrain Analysis, and start the Aspect tool.
- Prepare the input: Select the Input DEM raster file and confirm that the input data is complete and readable.
- Set core parameters: Configure the Z-axis scale factor according to the analysis objective.
- Set the output: Specify the Output aspect raster file and confirm that the output path, format, and naming rules meet later workflow requirements.
- 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.