Download or read elevation (SRTM-style DEM) — geo

Fetches a digital elevation model for a bounding box or set of sites, with an on-disk cache and an offline path for local GeoTIFFs. Prefers geodata (SRTM via elevation_*) when installed, then elevatr, then a user-supplied file. Cite Jarvis et al. (2008) / NASA SRTM when publishing maps that use these surfaces.

Usage

geo_elevation(
  data = NULL,
  lon = lon,
  lat = lat,
  bbox = NULL,
  path = NULL,
  cache_dir = NULL,
  download = TRUE,
  z = 5,
  buffer = 0.1
)

Arguments

data: Optional data frame of sites with lon/lat used to build the bounding box when bbox is NULL.
lon, lat: Coordinate columns of data.
bbox: Numeric vector c(xmin, ymin, xmax, ymax) in WGS84, or an sf / SpatExtent object.
path: Local GeoTIFF (or directory of GeoTIFFs) for offline use.
cache_dir: Cache directory. Defaults to tools::R_user_dir("tidymapr", "cache")/elevation.
download: Download when the cache is empty? Set FALSE on CRAN or offline runners.
z: Zoom / resolution hint for elevatr (1-14). Ignored by geodata.
buffer: Extra degrees added around the site bbox (default 0.1).

Value

A terra::SpatRaster elevation surface (metres).

References

Jarvis, A., Reuter, H. I., Nelson, A. and Guevara, E. (2008). Hole-filled SRTM for the globe Version 4. CGIAR-CSI. https://srtm.csi.cgiar.org/

Examples

dem <- geo_example_dem()
terra::nlyr(dem)
#> [1] 1