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Downloads, cache, and reproducibility

bluertopo_download() is for workflows where the durable deliverable is the original NOAA BlueTopo source file set. The function preserves NOAA basenames, keeps GeoTIFF and RAT sidecar files unmodified, verifies SHA-256 checksums by default, and writes manifests for future auditing.

Plan first

plan <- bluertopo_download(
  aoi,
  path = file.path(tempdir(), "bluertopo-downloads"),
  coverage = "fill",
  dry_run = TRUE
)

Dry runs return planned assets without creating the destination directory.

Download with verification

manifest <- bluertopo_download(
  aoi,
  path = file.path(tempdir(), "bluertopo-downloads"),
  rat = TRUE,
  verify = "sha256",
  on_exists = "verify"
)

Each row records the tile identifier, asset type, source URL, destination path, verification status, SHA-256 value, attempts, and timestamps. A fixed manifest is written at the download root for convenience, and query-addressed manifest copies are written under manifests/ when a query hash is available.

Existing files

on_exists = "verify" reuses an existing file only when verification succeeds. on_exists = "skip" records a skipped file without verification. on_exists = "replace" redownloads the asset.

reused <- bluertopo_download(
  aoi,
  path = file.path(tempdir(), "bluertopo-downloads"),
  on_exists = "verify"
)

Package cache

bluertopo() uses the package cache for catalog files, downloaded source assets, and VRTs. Cache roots are marked with .bluertopo-cache.json before package-owned content is written. The default cache is session-temporary; set options(bluertopo.cache_dir = "/path/to/cache") when a persistent cache is wanted.

bluertopo_cache_dir()

bluertopo_cache_clear() clears only the configured package cache. It refuses unmarked directories, suspicious roots, and symlinked cache paths.

bluertopo_cache_clear(confirm = TRUE)

Concurrency and retries

Downloads are currently deterministic and single-worker. workers = NULL and workers = 1 are accepted; higher values are rejected until bounded parallel downloads are implemented. Individual assets still use retry/backoff behavior for transient transfer failures.

manifest <- bluertopo_download(
  aoi,
  path = file.path(tempdir(), "bluertopo-downloads"),
  workers = 1,
  retries = 3
)

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.
Health stats visible at Monitor.