Resolution policies

BlueTopo tile metadata records each source tile’s native cell size. Smaller meter values mean finer source detail. In bluertopo, resolution chooses which source tiles to use; output_resolution creates a new output grid and therefore resamples.

Shortcuts

# Use every intersecting native source resolution.
bluertopo(aoi, resolution = "native")

# Prefer the finest available native source tiles.
bluertopo(aoi, resolution = "finest")

# Prefer the coarsest available native source tiles.
bluertopo(aoi, resolution = "coarsest")

# Keep all available resolutions as candidates.
bluertopo(aoi, resolution = "best_available")

Exact and nearest values

Numeric resolution values request exact native meter values. Use bluertopo_resolution() for explicit nearest-neighbor behavior.

bluertopo(aoi, resolution = 8)

bluertopo(
  aoi,
  resolution = bluertopo_resolution(
    "nearest",
    value = 10,
    tie = "finer"
  )
)

Ranges and ranks

bluertopo(
  aoi,
  resolution = bluertopo_resolution("between", min_m = 4, max_m = 16)
)

bluertopo(
  aoi,
  resolution = bluertopo_resolution("finest_n", n = 2)
)

n must be a positive whole number. Fractional values are rejected rather than silently truncated.

Coverage-oriented selection

Coverage diagnostics compare selected tile coverage against all published tile coverage intersecting the AOI. coverage = "fill" adds fallback native resolutions until the target is met or no fallback remains.

bluertopo(
  aoi,
  resolution = "finest",
  coverage = "fill",
  min_coverage = 0.95
)

policy <- bluertopo_resolution(
  "coverage",
  prefer = "finest",
  min_coverage = 0.90
)

bluertopo(aoi, resolution = policy, coverage = "fill")

For strategy = "coverage", the coverage target stored in the resolution policy is used. For other strategies, the function-level min_coverage argument is used.

Scope

Only global resolution ranking is currently implemented. scope = "local" is reserved for a future AOI-local ranking implementation and is rejected in this release instead of being accepted without effect.

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