tri | R Documentation |
Terrain Ruggedness Index is a measurement developed by Riley, et al. (1999). The elevation difference between the centre pixel and its eight immediate pixels are squared and then averaged and its square root is taken to get the TRI value. This function allows to calculate terrain ruggedness index (tri) statistics for polygons. For each polygon, the desired statistic(s) are returned.
calc_tri(engine = "extract", stats = "mean")
engine |
The preferred processing functions from either one of "zonal", "extract" or "exactextract" as character. |
stats |
Function to be applied to compute statistics for polygons either single or multiple inputs as character. Supported statistics are: "mean", "median", "sd", "min", "max", "sum" "var". |
The range of index values and corresponding meaning:
0-80 m - level surface
81-116 m - nearly level surface
117-161 m - slightly rugged surface
162-239 m - intermediately rugged surface
240-497 m - moderately rugged surface
498-958 m - highly rugged surface
959-4367 m extremely rugged surface
The required resources for this indicator are:
nasa_srtm
A function that returns an indicator tibble with tri as variable and the respective statistic as value.
Riley, S. J., DeGloria, S. D., & Elliot, R. (1999). Index that quantifies topographic heterogeneity. Intermountain Journal of Sciences, 5(1-4), 23-27.
## Not run:
library(sf)
library(mapme.biodiversity)
outdir <- file.path(tempdir(), "mapme-data")
dir.create(outdir, showWarnings = FALSE)
mapme_options(
outdir = outdir,
verbose = FALSE
)
aoi <- system.file("extdata", "sierra_de_neiba_478140_2.gpkg",
package = "mapme.biodiversity"
) %>%
read_sf() %>%
get_resources(get_nasa_srtm()) %>%
calc_indicators(
calc_tri(stats = c("mean", "median", "sd", "var"), engine = "extract")
) %>%
portfolio_long()
aoi
## End(Not run)
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