Problem: The Kernel Density tool does not generate the expected output in ArcMap
In some instances, the Kernel Density tool generates a blank output with a very small extent. In other cases, wrong density values are generated.
To check the extent of the layer, right-click the layer, click Properties, and click the Source tab.
The issue occurs because the projection of the data is in a geographic coordinate system (GCS). To use the tool, the data must be in a projected coordinate system (PCS) that has a linear unit of measurement because the tool calculates the number of features per unit area.
Examples of linear units of measurement are feet, meters, kilometers, and so forth.
A GCS uses decimal degrees based on a spheroid as its units of measure, and is therefore, subject to spatial distortion that affects the accuracy of distance.
Solution or Workaround
Re-project the data into a suitable PCS using the Project (Data Management) tool. For more information about this tool, refer to the following ArcGIS Help document, Project (Data Management).
- ArcGIS Help: Kernel Density (Spatial Analyst)
- ArcGIS Help: What are geographic coordinate systems?
- ArcGIS Help: What are projected coordinate systems?
- Blog: About geographic transformations and how to choose the right one
- Blog: How should I interpret the output of density tools?
- FAQ: Why do the distance measurements in ArcMap display in degrees instead of linear units?
- FAQ: Projection Basics: What the GIS professional needs to know