Get BlueTopo

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Get BlueTopo

bluertopo() is the main workflow for opening BlueTopo source bathymetry with terra. It discovers the current BlueTopo tile-scheme catalog, intersects that catalog with an area of interest, downloads verified original source files when needed, and returns file-backed terra rasters.

Define an AOI

Every AOI must resolve to polygon or multipolygon geometry. terra, sf, and file inputs must carry a known coordinate reference system (CRS).

Input type	Accepted form	CRS handling
`terra` vector	`SpatVector`	Uses the object’s CRS
`sf` vector	`sf` or `sfc`	Uses the object’s CRS
`terra` raster	`SpatRaster`	Uses its extent and CRS
`terra` extent	`SpatExtent`	Assumed EPSG:4326
Numeric bbox	`c(xmin, ymin, xmax, ymax)`	Assumed EPSG:4326
Local vector file	A path readable by `terra::vect()`	Uses the file’s CRS
Geometry text	WKT or GeoJSON polygon text	Assumed EPSG:4326

Remote URLs are intentionally refused. Points, lines, missing CRS values, unordered bounding boxes, and invalid longitude/latitude bounds fail early with an explanatory bluertopo_error_aoi condition.

library(bluertopo)

aoi <- vect("project_area.gpkg")

# Or a bbox: c(xmin, ymin, xmax, ymax) in EPSG:4326.
aoi <- c(xmin = -74.045, ymin = 40.675, xmax = -73.995, ymax = 40.715)

Pass sf objects directly; no conversion is required:

library(sf)

aoi_sf <- st_read("project_area.gpkg", quiet = TRUE)
bathy <- bluertopo(aoi_sf)

Discover tiles first

Inspect tile choices before downloading large GeoTIFFs.

tiles <- bluertopo_tiles(aoi)

as.data.frame(tiles)[
  c("tile_id", "resolution_m", "delivered_date", "selection_reason")
]

Open bathymetry

By default, bluertopo() downloads original NOAA assets into the package cache, verifies SHA-256 checksums, and opens the elevation band.

result <- bluertopo(aoi, details = TRUE)

result$data
result$downloads
result$coverage

Set details = TRUE when provenance matters. The result includes selected tiles, download statuses, query metadata, coverage diagnostics, and catalog provenance.

Know what comes back

Call	Return value
`bluertopo_tile_polygons()`	A `terra::SpatVector` of every current tile footprint; no AOI required
`bluertopo_tiles(aoi)`	A `terra::SpatVector` of selected tile footprints and metadata
`bluertopo_download(aoi, path)`	A `bluertopo_downloads` data frame with one row per asset
`bluertopo(aoi)`	A `terra::SpatRaster`, or a `terra::SpatRasterCollection` for incompatible native grids
`bluertopo(aoi, details = TRUE)`	A `bluertopo_result` list containing `data`, `tiles`, `downloads`, `query`, `coverage`, and `provenance`

Choose layers

BlueTopo source GeoTIFFs currently expose elevation, vertical uncertainty, and contributor/source identifier bands.

all_layers <- bluertopo(
  aoi,
  layers = "all",
  coverage = "fill"
)

Avoid accidental resampling

Native BlueTopo tiles may differ in CRS, resolution, origin, or alignment. When selected source grids are incompatible, bluertopo() returns a terra::SpatRasterCollection rather than silently resampling.

Request a single output grid only when resampling is an intentional analytical choice.

bathy_10m <- bluertopo(
  aoi,
  resolution = "native",
  output_crs = "EPSG:26918",
  output_resolution = 10,
  combine = "single"
)

crop = TRUE crops to the AOI extent. mask = TRUE additionally removes cells outside the polygon. combine = "auto" preserves compatible native grids as one raster and returns a collection for incompatible grids. Supplying both output_crs and output_resolution creates one explicit resampled output grid.

These binaries (installable software) and packages are in development.
They may not be fully stable and should be used with caution. We make no claims about them.