SDMTools (version 1.1-11)

slope: Slope and aspect calculations

Description

slope and aspect calculates the slope and aspect of raster surfaces of class 'asc' (SDMTools & adehabitat packages), 'RasterLayer' (raster package) or 'SpatialGridDataFrame' (sp package). Methods are based on Burrough and McDonell (1998).

Usage

slope(mat,latlon=FALSE)
aspect(mat,latlon=FALSE)

Arguments

mat

a matrix of data representing z heights. Matrix can be a raster of class 'asc' (adehabitat package), 'RasterLayer' (raster package) or 'SpatialGridDataFrame' (sp package)

latlon

boolean value representing if the data is geographic.

Value

• an object of the same class as mat.

Details

Slope returns values representing the 'rise over run' with "run" units representing cellsize if latlon=FALSE or km if latlon=TRUE. This can be changed to percentage (multiply by 100) or to degrees by ATAN ( output ) * 57.29578. Aspect returns the direction (0 to 360) with North being 0. Values of -1 are flat areas with no slope or aspect. As this method requires information from the surrounding cells, missing data (NAs or edges) are populated with the value from the 'cell-of-interest').

References

Burrough, P. A. and McDonell, R.A., 1998. Principles of Geographical Information Systems (Oxford University Press, New York), p. 190.

Examples

#define a simple asc with some slope and direction
tasc = as.asc(matrix(1:50,nr=10,nc=5),yll=75); tasc[,]
slope(tasc)[,] #show the output of slope
aspect(tasc)[,] #show the output of the aspect

#define a FLAT simple asc 
tasc = as.asc(matrix(10,nr=10,nc=5),yll=75); tasc[,]
slope(tasc)[,] #show the output of slope
aspect(tasc)[,] #show the output of the aspect