Examples Slope Angle Derived from the Neighborhood Slope Algorithm (also referred to as the average maximum technique)

To understand how slope angle is calculated from elevation data with the neighborhood method in GIS, access the Understanding the neighborhood slope algorithm page. With this common slope angle algorithm, the cell that slope angle is being calculated for in the moving window, the center cell, is not used in the calculation; all eight cells around the center cell are used.

In all the examples that follow, elevation around center cell is in feet and cell (pixel) size is 10 feet:

 10,020 10,020 10,020 10,010 N/A 10,010 10,000 10,000 10,000

Neighborhood slope angle for center cell = 45.0°

Comparison group; bold number after first group shows elevation value changed from first group

 10,020 10,010 10,000 10,020 N/A 10,000 10,020 10,010 10,000

Neighborhood slope angle for center cell = 45.0°

 10,010 10,010 10,000 10,020 N/A 10,000 10,020 10,010 10,000

Neighborhood slope angle for center cell = 41.5°

 10,020 10,010 10,000 10,010 N/A 10,000 10,020 10,010 10,000

Neighborhood slope angle for center cell = 36.9°

 10,020 10,010 10,000 10,020 N/A 10,000 10,010 10,010 10,000

Neighborhood slope angle for center cell = 41.5°

Comparison group; bold number after first group shows elevation value/s changed from first group

 10,000 10,010 10,000 10,000 N/A 10,000 10,000 10,010 10,000

Neighborhood slope angle for center cell = 0.0°

 10,000 10,000 10,000 10,010 N/A 10,010 10,000 10,000 10,000

Neighborhood slope angle for center cell = 0.0°

 10,000 10,010 10,000 10,010 N/A 10,010 10,000 10,010 10,000

Neighborhood slope angle for center cell = 0.0°

 10,010 10,000 10,000 10,000 N/A 10,000 10,000 10,000 10,000

Neighborhood slope angle for center cell = 10.0°

 10,000 10,000 10,000 10,010 N/A 10,000 10,000 10,000 10,000

Neighborhood slope angle for center cell = 14.0°

Comparison group; bold number after first group shows elevation value/s changed from first group

 10,016 10,016 10,016 10,008 N/A 10,008 10,000 10,000 10,000

Neighborhood slope angle for center cell = 38.7°

 10,016 10,016 10,011 10,008 N/A 10,008 10,000 10,000 10,000

Neighborhood slope angle for center cell = 36.5°

 10,016 10,011 10,011 10,008 N/A 10,008 10,000 10,000 10,000

Neighborhood slope angle for center cell = 31.6°

 10,011 10,011 10,011 10,008 N/A 10,008 10,000 10,000 10,000

Neighborhood slope angle for center cell = 28.8°