Trik2.numeric: Improved TRI (with differences of order 2), reducing/removing...

In SurfRough: Calculate Surface/Image Texture Indexes

Improved TRI (with differences of order 2), reducing/removing slope dependence.

Description

It is essentially a radial roughness index. TRIk2 modifies TRI (topographic ruggedness index) using increments of order 2, symmetrical to central pixel, so as to remove the effect of local slope. This version does not correct for diagonal distance and therefore is mainly for testing/simulation purposes, so in practice the Radial Roughness Index calculated by the RRI function should be used instead. It uses a 5x5 kernel, consequently 12 directional differences of order k (2) are used in the estimation. One could also use a 3x3 kernel using only the 4 differences centered on the central pixel but the metric would be very noisy. The input is the DEM (no need to detrend).

Usage

## S3 method for class 'numeric'
Trik2(x)

Arguments

x	A vector of numeric values from a focal window in a DEM from which to compute the index

Value

isotropic roughness (in the same units of input)

References

1. Riley, S. J., S. D. DeGloria, and R. Elliott. 1999. A terrain ruggedness index that quantifies topographic heterogeneity. Intermountain Journal of Science 5:23.

2. Wilson, M.F.J., O'Connell, B., Brown, C., Guinan, J.C. & Grehan, A.J. 2007. Multiscale terrain analysis of multibeam bathymetry data for habitat mapping on the continental slope". Marine Geodesy, vol. 30, no. 1-2, pp. 3-35.

3. Trevisani S., Teza G., Guth P.L., 2023. Hacking the topographic ruggedness index. Geomorphology https://doi.org/10.1016/j.geomorph.2023.108838

Examples

library(terra)
dem=rast(paste(system.file("extdata", package = "SurfRough"), "/trento1.tif",sep=""))
w <- matrix(1, nrow=5, ncol=5)
roughTrik5x5=focal(dem, w=w, fun=Trik2)
plot(roughTrik5x5)

SurfRough documentation built on April 4, 2025, 2:19 a.m.