get_aws_terrain: Get a digital elevation model from the AWS Terrain Tiles

Description

This function uses the AWS Terrain Tile service to retrieve an elevation raster from the geotiff service. It accepts a sp::bbox object as input and returns a single raster object covering that extent.

Usage

get_aws_terrain(
  locations,
  z,
  prj,
  expand = NULL,
  ncpu = future::availableCores() - 1,
  serial = NULL,
  ...
)

Arguments

z: The zoom level to return. The zoom ranges from 1 to 14. Resolution of the resultant raster is determined by the zoom and latitude. For details on zoom and resolution see the documentation from Mapzen at https://github.com/tilezen/joerd/blob/master/docs/data-sources.md#what-is-the-ground-resolution
prj: A string defining the projection of the locations argument. The string needs to be an acceptable SRS_string for CRS-class for your version of PROJ. If a sf object, a sp object or a raster object is provided, the string will be taken from that. This argument is required for a data.frame of locations.
expand: A numeric value of a distance, in map units, used to expand the bounding box that is used to fetch the terrain tiles. This can be used for features that fall close to the edge of a tile and additional area around the feature is desired. Default is NULL.
ncpu: Number of CPU's to use when downloading aws tiles.
serial: Logical to determine if API should be hit in serial or in parallel. TRUE will use purrr, FALSE will use furrr.
...: Extra configuration parameters to be passed to httr::GET. Common usage is to adjust timeout. This is done as config=timeout(x) where x is a numeric value in seconds. Multiple configuration functions may be passed as a vector.
bbx: a sp::bbox object that is used to select x,y,z tiles.