To smooth contour lines when generating them from a raster dataset in ArcGIS Pro, you typically use a geoprocessing tool like the Contour tool and specify a value for Adaptive Smoothing.
Smoothing contour lines can improve their aesthetic appearance and readability, especially in areas with rough terrain or noisy elevation data. In ArcGIS Pro, when creating contour lines directly from a raster source (like a Digital Elevation Model or DEM), you have the option to apply smoothing during the generation process itself.
Generating Smoothed Contours from a Raster
The primary method for smoothing contour lines based on the provided reference involves using a geoprocessing tool designed to create contours from raster data. This process includes a specific parameter for controlling the smoothing level.
Here are the key steps involved, as indicated by the reference:
- Select the Raster Layer: Begin by identifying and selecting the input raster layer containing the elevation data (e.g., your DEM) from the appropriate dropdown list or tool interface. This raster is the source from which the contour lines will be derived.
- Specify Adaptive Smoothing: This is the crucial step for smoothing. You need to specify a value for the Adaptive Smoothing parameter. This parameter controls how much the resulting contour lines are generalized or smoothed. Higher values result in smoother, less jagged lines, but may also slightly shift the position of the contours relative to the original raster data. Experimenting with different values is often necessary to find the desired balance between smoothness and positional accuracy.
- Set Contour Type: For generating standard contour lines, ensure that the Contour Type option is set to the default Contour lines. This confirms that the output will be vector lines representing points of equal elevation.
- Specify Z Base: Define the base contour value (Z Base). This sets the starting elevation for contour generation. Along with the contour interval, this determines the specific elevations for which contour lines will be created.
These steps are typically found within a geoprocessing tool specifically designed for generating contours from raster datasets in ArcGIS Pro.
Understanding Adaptive Smoothing
Adaptive Smoothing works by simplifying the geometry of the contour lines as they are created. Instead of generating lines that precisely follow every pixel variation in the raster (which can lead to very jagged lines), the smoothing process generalizes the lines based on the specified smoothing tolerance. The 'adaptive' aspect often means the smoothing is applied more or less depending on the local complexity of the terrain.
Smoothing Existing Vector Contour Lines
It's important to note that the method described above is for smoothing contours during the generation process from a raster. If you already have existing contour lines as vector features (polylines) and want to smooth them, you would use different geoprocessing tools designed for generalizing or smoothing vector features. Examples include tools like:
- Smooth Line: This tool modifies the shape of input line features to make them appear smoother, typically using algorithms like PAEK, Bezier interpolation, or B-spline.
- Generalize: While primarily used for reducing vertex count, this tool can also result in smoother appearances depending on the chosen algorithm (e.g., Simplify Line or Simplify Polygon).
However, the reference specifically points to parameters used in the raster-to-contour generation process, highlighting the "Adaptive Smoothing" option available at that stage.
