In the previous chapter, you've calculated a non-spatial result for the drainage density of a catchment. In this chapter we'll use the Line density tool to calculate a more spatially explicit result.
1.Click 
in the toolbar to open the Processing Toolbox panel.
2. In the Processing Toolbox, double click on the Interpolation | Line density tool.
3. In the Line density dialog, choose Dissolved as the Input line layer. Change the Search radius to 10 km and the Pixel size to 1 km. These values depend on the size and properties of your catchment.
4. Keep the rest as default and click Run. Click Close after processing.
5. Style the result with a ramp.
