Create vector tiles from spatial data

Creates a PMTiles archive containing vector tiles from one or more sf data frames. Supports both Mapbox Vector Tile (MVT) and MapLibre Tile (MLT) formats, multi-layer output, feature dropping, point clustering, and feature coalescing.

Usage

freestile(
  input,
  output,
  layer_name = NULL,
  tile_format = "mlt",
  min_zoom = 0L,
  max_zoom = 14L,
  base_zoom = NULL,
  drop_rate = NULL,
  cluster_distance = NULL,
  cluster_maxzoom = NULL,
  coalesce = FALSE,
  simplification = TRUE,
  generate_ids = TRUE,
  overwrite = TRUE,
  quiet = FALSE
)

Arguments

input

An sf data frame, or a named list of sf/freestile_layer objects for multi-layer output.

output

Character. Path for the output .pmtiles file.

layer_name

Character. Name for the tile layer. If NULL, derived from the output filename. Only used for single-layer input.

tile_format

Character. Tile encoding format: "mlt" (default) for MapLibre Tiles or "mvt" for Mapbox Vector Tiles.

min_zoom

Integer. Minimum zoom level (default 0).

max_zoom

Integer. Maximum zoom level (default 14).

base_zoom

Integer. Zoom level at and above which all features are present (no dropping). NULL (default) uses each layer's own max_zoom. The drop-rate curve is also computed relative to base_zoom, so lowering it produces gentler thinning at low zooms. Inspired by tippecanoe's -B / --base-zoom.

drop_rate

Numeric. Exponential drop rate for feature thinning (e.g. 2.5). At each zoom level below base_zoom, features are retained at a rate of 1/drop_rate^(base_zoom - zoom). Points are thinned using spatial ordering; polygons/lines are thinned by area. NULL (default) disables drop-rate thinning.

cluster_distance

Numeric. Pixel distance for point clustering. Points within this radius are merged into cluster features with a point_count attribute. NULL (default) disables clustering.

cluster_maxzoom

Integer. Maximum zoom level for clustering. Above this zoom, individual points are shown. Default is max_zoom - 1.

coalesce

Logical. Whether to merge features with identical attributes within each tile (default FALSE). Lines sharing endpoints are merged; polygons are grouped into MultiPolygons.

simplification

Logical. Whether to snap geometries to the tile pixel grid at each zoom level (default TRUE). This provides zoom-adaptive simplification and prevents slivers between adjacent polygons.

generate_ids

Logical. Whether to assign sequential feature IDs (default TRUE).

overwrite

Logical. Whether to overwrite existing output file (default TRUE).

quiet

Logical. Whether to suppress progress messages (default FALSE).

Value

The output file path (invisibly).

Examples

if (FALSE) { # \dontrun{
library(sf)
nc <- st_read(system.file("shape/nc.shp", package = "sf"))

# Single layer
freestile(nc, "nc.pmtiles", layer_name = "counties")

# Multi-layer
pts <- st_centroid(nc)
freestile(
  list(counties = nc, centroids = pts),
  "nc_layers.pmtiles"
)

# With dropping and coalescing
freestile(nc, "nc_drop.pmtiles", drop_rate = 2.5, coalesce = TRUE)

# With point clustering
freestile(pts, "pts.pmtiles", cluster_distance = 50, cluster_maxzoom = 8)
} # }