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Convert geometries to QuadKey tiles

Source: R/ddbs_quadkey.R
ddbs_quadkey.Rd

Converts POINT geometries to QuadKey tile representations at a specified zoom level. QuadKeys are a hierarchical spatial indexing system used by mapping services like Bing Maps.

Usage

ddbs_quadkey(
  x,
  level = 10,
  output = "polygon",
  field = NULL,
  fun = "mean",
  background = NA,
  conn = NULL,
  name = NULL,
  crs = NULL,
  crs_column = "crs_duckspatial",
  overwrite = FALSE,
  quiet = FALSE
)

Arguments

x

An sf spatial object. Alternatively, it can be a string with the name of a table with geometry column within the DuckDB database conn. Data is returned from this object.

level

An integer specifying the zoom level for QuadKey generation (1-23). Higher values provide finer spatial resolution. Default is 10.

output

Character string specifying output format. One of:

  • "polygon" - Returns QuadKey tile boundaries as polygons (default)

  • "raster" - Returns QuadKey values as a raster grid

  • "tilexy" - Returns tile XY coordinates

field

Character string specifying the field name for raster output. Only used when output = "raster"

fun

summarizing function for when there are multiple geometries in one cell (e.g. "mean", "min", "max", "sum"). Only used when output = "raster"

background

numeric. Default value in raster cells without values. Only used when output = "raster"

conn

A connection object to a DuckDB database. If NULL, the function runs on a temporary DuckDB database.

name

A character string of length one specifying the name of the table, or a character string of length two specifying the schema and table names. If NULL (the default), the function returns the result as an sf object

crs

The coordinates reference system of the data. Specify if the data doesn't have a crs_column, and you know the CRS.

crs_column

a character string of length one specifying the column storing the CRS (created automatically by ddbs_write_vector). Set to NULL if absent.

overwrite

Boolean. whether to overwrite the existing table if it exists. Defaults to FALSE. This argument is ignored when name is NULL.

quiet

A logical value. If TRUE, suppresses any informational messages. Defaults to FALSE.

Value

An sf object or TRUE (invisibly) for table creation

Details

QuadKeys divide the world into a hierarchical grid of tiles, where each tile is subdivided into four smaller tiles at the next zoom level. This function wraps DuckDB's ST_QuadKey spatial function to generate these tiles from input geometries.

Examples

if (FALSE) { # \dontrun{
## load packages
library(duckspatial)
library(sf)
library(terra)

# create a duckdb database in memory (with spatial extension)
conn <- ddbs_create_conn(dbdir = "memory")

## create random points in Argentina
argentina_sf <- st_read(system.file("spatial/argentina.geojson", package = "duckspatial"))
rand_sf <- st_sample(argentina_sf, 100) |> st_as_sf()
rand_sf["var"] <- runif(100)

## store in duckdb
ddbs_write_vector(conn, rand_sf, "rand_sf")

## generate QuadKey polygons at zoom level 8
qkey_sf <- ddbs_quadkey(conn = conn, "rand_sf", level = 8, output = "polygon")

## generate QuadKey raster with custom field name
qkey_rast <- ddbs_quadkey(conn = conn, "rand_sf", level = 6, output = "raster", field = "var")

## generate Quadkey XY tiles
qkey_tiles_tbl <- ddbs_quadkey(conn = conn, "rand_sf", level = 10, output = "tilexy")
} # }