The slope is the terrain surface inclination in relation to the horizontal plane. Considering a terrain numeric model (TNM) with height data fetched from a topographic chart and plotting a tangent plane to this surface in a determined point (P), the slope in P will correspond to the inclination of this plan in relation to the horizontal plan.
In some geological, geomorphic applications it is necessary to find regions with few obstacles or regions exposed to the sun during certain day periods. To answer those questions slope counts with two components: gradient and exposition.
Gradient is the maximum variation rate in elevation value, it can be measured in grades (0 to 90º) or in percentage (%), in TerraAmazon called slope; and exposition is the direction of this measure variation in grades (0 to 360º).
Be sure that a rectangle grid was generated to the layer in the wanted numeric category.
Select PROCESSING → DTM PROCESSING → SLOPE in the main menu.
Input Layer Name: click on the Search button and choose a layer.
Dummy Value: check in this box to enter the pixel dummy value. This dummy value will be ignored by the operation.
Compute: choose slope or aspect
Slope Unit: choose between degrees or percent (only for slope option).
Raster Parameters: shows the values for resolution XY and dimension CL.
Repository:
Click on the icon
to save the result in a shape file.
Output Layer Name: Enter the name of the resulting image.
Click on the OK button.
Note: once slope grid or aspect grid is created, slicing should be done on it to obtain a thematic map that represents slope/aspect interval as desired.