Extract Digital Elevation Model — dem • spatialBACI

Read Digital Elevation Model and calculate derivatives.

Usage

dem(
  x,
  dem_source,
  v = c("elevation", "slope", "aspect"),
  neighbors = 8,
  unit = "radians",
  transformAspect = TRUE,
  ...
)

# S4 method for class 'SpatRaster'
dem(
  x,
  dem_source,
  v = c("elevation", "slope", "aspect"),
  neighbors = 8,
  unit = "radians",
  transformAspect = TRUE
)

# S4 method for class 'SpatExtent'
dem(
  x,
  dx,
  dy,
  srs,
  dem_source,
  v = c("elevation", "slope", "aspect"),
  neighbors = 8,
  unit = "radians",
  transformAspect = TRUE
)

# S4 method for class 'SpatVector'
dem(
  x,
  dx,
  dy,
  dem_source,
  v = c("elevation", "slope", "aspect"),
  neighbors = 8,
  unit = "radians",
  transformAspect = TRUE
)

Arguments

x: a SpatRaster, spatVector, or SpatExtent object, defining the area for which the DEM should be extracted
dem_source: Source of the Digital Elevation Model, see Details
v: character vector. Terrain parameters to be calculated
neighbors: integer. Either 8 (queen case) or 4 (rook case), indicating which neighbors to use to compute slope or aspect.
unit: character. "degrees" or "radians" for the output of slope and aspect
transformAspect: logical. Should aspect be transformed to "northness" and "eastness"
...: Additional arguments passed to the relevant method
dx: numeric. Output resolution in x dimension
dy: numeric. Output resolution in y dimension
srs: character. output spatial reference system

Value

a data cube, SpatRaster or SpatVector object (see Details)

Details

This function returns a data cube object when only the digital terrain model is required (i.e. v="elevation"), and a SpatRaster when the terrain derivatived are required. The reason for this is that calculating terrain parameters using the terra::terrain function outperforms the same calculation on data cube, with regard to time.

dem_source must be a list with STAC specifications (named list with list elements "endpoint", "collection", "assets" and (optionally) "authOpt". If no DEM source it provided, this argument defaults to list(endpoint="https://planetarycomputer.microsoft.com/api/stac/v1", collection="nasadem", assets="elevation", authOpt=list())

Examples of available global DEMs with STAC endpoint/collection/assets specification and whether authentication is required to access the DEM:

name	endpoint	collection	assets	auth.

NASA DEM (default)	https://planetarycomputer.microsoft.com/api/stac/v1	"nasadem"	"elevation"	no
ALOS World DEM 30m	https://planetarycomputer.microsoft.com/api/stac/v1	"alos-dem"	"data"	no
Copernicus DEM 30m	https://planetarycomputer.microsoft.com/api/stac/v1	"cop-dem-glo-30"	"data"	yes
Copernicus DEM 90m	https://planetarycomputer.microsoft.com/api/stac/v1	"cop-dem-glo-90"	"data"	yes