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Fetch static bathymetry for a study area

Source: R/bathymetry.R
fetch_bathymetry.Rd

Downloads NOAA ETOPO bathymetry via marmap::getNOAA.bathy() and derives slope and aspect from it.

Usage

fetch_bathymetry(
  bounding_box,
  resolution = 4,
  path = copernicus_cache("bathymetry"),
  keep = TRUE
)

Arguments

bounding_box

named list with xmin, xmax, ymin, ymax

resolution

grid resolution in arc-minutes, as marmap defines it; smaller is finer and slower. 4 is roughly 7 km at mid latitudes.

path

directory for the download cache; created if absent. Defaults to a bathymetry folder under tools::R_user_dir(), so downloads persist between sessions.

keep

whether marmap should cache the downloaded grid for reuse. With FALSE nothing is written, so nothing can be read back later either.

Value

a terra::SpatRaster with one layer per variable in bathymetry_variables(), in EPSG:4326

Citation

The grid is NOAA NCEI ETOPO 2022, requested at 60 arc-second bedrock resolution through marmap. Both want citing when the result is published:

  • NOAA National Centers for Environmental Information (2022). ETOPO 2022 15 Arc-Second Global Relief Model. doi:10.25921/fd45-gt74

  • Pante E, Simon-Bouhet B, Irisson J (2025). marmap: Import, Plot and Analyze Bathymetric and Topographic Data. doi:10.32614/CRAN.package.marmap

The bounding box takes the same shape as accessEnvDat()'s, so a single definition of the study area serves both.

Caching

marmap caches downloads into the working directory by default, which scatters them wherever R happened to be started. This puts them beside the Copernicus cache instead, under tools::R_user_dir(), so a study area downloaded once stays downloaded across sessions. path overrides that.

A grid already on disk is read with marmap::read.bathy() rather than re-requested through marmap::getNOAA.bathy(). Both return the same object, but the second announces itself — "Querying NOAA database", then "File already exists ; loading ..." — and there is no reason to narrate a local file read. Reading directly also skips the NOAA round trip entirely.

Examples

if (FALSE) { # \dontrun{
bathy <- fetch_bathymetry(
  bounding_box = list(xmin = -70, xmax = -66, ymin = 41, ymax = 44)
)
terra::plot(bathy[["DEPTH"]])
} # }