Solar-radiation Aspect Index — trasp • spatialEco

Calculates the Roberts and Cooper (1989) Solar-radiation Aspect Index

Roberts and Cooper (1989) rotates (transforms) the circular aspect to assign a value of zero to land oriented in a north-northeast direction, (typically the coolest and wettest orientation), and a value of one on the hotter, dryer south-southwesterly slopes. The result is a continuous variable between 0 - 1. The metric is defined as: trasp = ( 1 - cos((pi/180)(a-30) ) / 2 where; a = aspect in degrees

trasp(x, ...)

Arguments

x	raster object
...	Additional arguments passed to raster::calc

Value

raster class object of oberts and Cooper (1989) Solar-radiation Aspect Index

References

Roberts. D.W., and Cooper, S.V. (1989). Concepts and techniques of vegetation mapping. In Land Classifications Based on Vegetation: Applications for Resource Management. USDA Forest Service GTR INT-257, Ogden, UT, pp 90-96

Author

Jeffrey S. Evans <jeffrey_evans@tnc.org>

Examples

  library(raster)
  data(elev)
  s <- trasp(elev)
    plot(s)