Tidy raster analysis verbs — geo-raster • tidymapr

Native tidyverse-style wrappers around common terra operations for elevation and climate rasters. terra (and therefore these helpers) reads and writes through GDAL, so GeoTIFF, COG, netCDF and similar formats work without calling gdal_translate yourself. Do not use the retired rgdal package. Pair with geo_extract() to join raster values to sites, and with geo_buffer() plus geo_raster_zonal() for mean elevation in a site buffer. geo_raster_project(), geo_raster_crop() and geo_raster_mask() are the tidy entry points for GDAL warps / clips.

Usage

geo_raster_crop(raster, y, ...)

geo_raster_mask(raster, y, ...)

geo_raster_resample(raster, res = NULL, method = "bilinear", ...)

geo_raster_project(raster, crs, method = "bilinear", ...)

geo_raster_terrain(
  raster,
  v = c("slope", "aspect", "TPI"),
  unit = "degrees",
  ...
)

geo_raster_focal(raster, w = 3, fun = "mean", ...)

geo_raster_zonal(raster, y, fun = "mean", ..., as_tibble = TRUE)

Arguments

raster: A terra::SpatRaster or a file path.
y: An sf polygon/line used to crop, mask or summarise.
...: Passed to the underlying terra helper.
res: Target resolution (one or two numbers) for resampling.
method: Resampling method passed to terra.
crs: Target CRS (EPSG code, WKT or proj string).
v: Terrain variables: "slope", "aspect", "TPI", "TRI", "roughness", "flowdir".
unit: Unit for slope/aspect ("degrees" or "radians").
w: Window size (odd integer or matrix) for the focal filter.
fun: Summary function name or function.
as_tibble: Return a tibble (default) instead of the raw terra extract matrix?

Examples

r <- terra::rast(ncols = 20, nrows = 20, xmin = 144.8, xmax = 145.4,
  ymin = -6.0, ymax = -5.5, crs = "EPSG:4326")
terra::values(r) <- seq_len(terra::ncell(r))
names(r) <- "elev"
sites <- geo_as_sf(geo_example_sites("wilhelm"), lon, lat)
sites <- sites[sites$elevation <= 2200, ]
geo_raster_zonal(r, geo_buffer(sites, dist = 2000), fun = "mean")
#> # A tibble: 5 × 7
#>   site     lon   lat elevation elevation_band coordinate_note               elev
#>   <chr>  <dbl> <dbl>     <int> <fct>          <chr>                        <dbl>
#> 1 MW0200  145. -5.74       200 200 m          published bait GPS, doi:10.…   198
#> 2 MW0700  145. -5.73       700 700 m          published bait GPS, doi:10.…   196
#> 3 MW1200  145. -5.72      1200 1200 m         published bait GPS, doi:10.…   186
#> 4 MW1700  145. -5.76      1700 1700 m         published bait GPS, doi:10.…   215
#> 5 MW2200  145. -5.76      2200 2200 m         published bait GPS, doi:10.…   213