R: Slope and aspect calculations

slope {SDMTools} | R Documentation

## 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.

### 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').

### Value

an object of the same class as `mat`.

### Author(s)

Jeremy VanDerWal jjvanderwal@gmail.com

### 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

[Package SDMTools version 1.1-221.2 Index]