# rumple_index

0th

Percentile

##### Rumple index of roughness

Computes the roughness of a surface as the ratio between its area and its projected area on the ground. If the input is a gridded object (lasmetric or raster) the function computes the surfaces using Jenness's algorithm (see references). If the input is a point cloud the function uses a Delaunay triangulation of the points and computes the area of each triangle.

##### Usage
rumple_index(x, y = NULL, z = NULL, ...)
##### Arguments
x

A 'RasterLayer' or a 'lasmetrics' object, or a vector of x point coordinates.

y

numeric. If x is a vector of coordinates: the associated y coordinates.

z

numeric. If x is a vector of coordinates: the associated z coordinates.

...

unused

##### Value

numeric. The computed Rumple index.

##### References

Jenness, J. S. (2004). Calculating landscape surface area from digital elevation models. Wildlife Society Bulletin, 32(3), 829<U+2013>839.

• rumple_index
##### Examples
# NOT RUN {
x = runif(20, 0, 100)
y = runif(20, 0, 100)

# Perfectly flat surface, rumple_index = 1
z = rep(10, 20)
rumple_index(x, y, z)

# Rough surface, rumple_index > 1
z = runif(20, 0, 10)
rumple_index(x, y, z)

# Rougher surface, rumple_index increases
z = runif(20, 0, 50)
rumple_index(x, y, z)

# Measure of roughness is scale-dependent
rumple_index(x, y, z)
rumple_index(x/10, y/10, z)

# Use with a canopy height model
LASfile <- system.file("extdata", "Megaplot.laz", package="lidR")