Menu | Tools > Bands > Compute Slope and Aspect |
Calculate the slope and aspect values for a raster surface.
Calculating the slope and aspect values for a surface uses a triangular network over the entire surface. The triangles in the network are formed by connecting the points in the surface. Every line connecting two points has a slope and each of the triangles touching at a point has an aspect. Only the maximum slope at each point is stored.
Slope is the maximum steepness from a node to all connected nodes within the TIN of the surface. It is measured in degrees (0 to 90).
Aspect is the direction of the steepest triangle involving the node, measured clockwise from north.
For surfaces using Geographic coordinates, the first step in the calculation of slope is to preform a degrees-to-metres conversion for the centre of the surface. This is then used throughout the surface.
Related commands:
Procedure
1. Select a raster surface in the Layers window.
This command can only be used on surfaces that have a primary Z band with Float type data. |
2. Select the Compute Slope and Aspect command.
BASE Editor will perform the computation based on the data in the selected surface.
When finished, a message indicating the start and end times is displayed in the Output window.
Two new bands are added to the coverage for the new data. These bands are not displayed automatically; the Add Layer command can be used to display the layers and their data. See Add Layer for more information.
3. Select an area in the Display window.
The Selection window displays all band values for the selected points, including the newly computed slope and aspect values.
In the Properties window you can choose to colour the data according to the new slope or aspect values. When Slope is selected, the Min and Max values for the Range property represent the minimum and maximum angle values in the data. The maximum value possible for slope is 90 degrees.