Aspect is calculated using the north-south and east-west gradients as expressed using the following equation:

Aspect = ArcTangent (dEW/dNS)

The above equation is adjusted to reflect aspect in degrees in a range from 0 to 360. Often -1 is used to represent a cell with no slope (skyward aspect) and the values from 0 to 360 represent azimuths in clockwise degrees from north. North is 0, East is 90 degrees, South is 180 degrees etc. Optionally, the result is then divided by 22.5 and converted to an integer to derive a set of generalized solar azimuths .

(or see the ArcView explanation)


aspect calculated for the Bellarine Peninsula

	represents non-sloping areas (flat)
	represents slopes facing the top edge of a map (north)
	represents slopes facing the upper right corner of a map (north east)
	represents slopes facing the right edge of the map (east)
	represents slopes facing the lower right corner of the map (south east)
	represents slopes facing the bottom edge of a map (south)
	represents slopes facing the left corner of a map (south west)
	represents slopes facing the left edge of a map (west)
	represents slopes facing the upper left corner of a map (north west)
	represents areas of no data