Determining aspect
Release 9.2 Last modified May 2, 2007	Print all topics in : "Surface analysis"

Aspect identifies the steepest downslope direction from each cell to its neighbors. It can be thought of as slope direction or the compass direction a hill faces.

Learn how to calculate aspect using the Spatial Analyst toolbar

Learn how to calculate aspect using the Aspect tool

Aspect is measured clockwise in degrees from 0, due north, to 360, again due north, coming full circle. The value of each cell in an aspect dataset indicates the direction the cell's slope faces. Flat areas having no downslope direction are given a value of -1.



The diagram below shows an input elevation dataset and the output aspect raster.

Why use the Aspect tool?

With the Aspect tool, you can:

• Find all north-facing slopes on a mountain as part of a search for the best slopes for ski runs.
  
• Calculate the solar illumination for each location in a region as part of a study to determine the diversity of life at each site.
  
• Find all southerly slopes in a mountainous region to identify locations where the snow is likely to melt first as part of a study to identify those residential locations likely to be hit by runoff first.
  
• Identify areas of flat land to find an area for a plane to land in an emergency.
  

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