trim_osmdata

Trim an osmdata object to within a bounding polygon

Usage

trim_osmdata(dat, bb_poly, exclude = TRUE)

Arguments

dat

An osmdata object returned from osmdata_sf() or osmdata_sc().

bb_poly

An sf or sfc object, or matrix representing a bounding polygon. Can be obtained with getbb (..., format_out = "polygon") or getbb (..., format_out = "sf_polygon") (and possibly selected from resultant list where multiple polygons are returned).

exclude

If TRUE, objects are trimmed exclusively, only retaining those strictly within the bounding polygon; otherwise all objects which partly extend within the bounding polygon are retained.

Value

A trimmed version of dat, reduced only to those components lying within the bounding polygon.

Note

It will generally be necessary to pre-load the sf package for this function to work correctly.

Caution is advised when using polygons obtained from Nominatim via getbb(..., format_out = "polygon"|"sf_polygon"). These shapes can be outdated and thus could cause the trimming operation to not give results expected based on the current state of the OSM data.

To reduce the downloaded data from Overpass, you can do the trimming in the server-side using getbb(..., format_out = "osm_type_id") (see examples).

See also

Other transform: osm_elevation(), osm_poly2line(), unique_osmdata(), unname_osmdata_sf()

Examples

if (FALSE) { # \dontrun{
bb <- getbb ("colchester uk")
query <- opq (bb) |>
    add_osm_feature (key = "highway")
# Then extract data from 'Overpass' API
dat <- osmdata_sf (query, quiet = FALSE)
# Then get bounding *polygon* for Colchester, as opposed to rectangular
# bounding box, and use that to trim data within that polygon:
bb_pol <- getbb ("colchester uk", format_out = "polygon")
library (sf) # required for this function to work
dat_tr <- trim_osmdata (dat, bb_pol)
bb_sf <- getbb ("colchester uk", format_out = "sf_polygon")
class (bb_sf) # sf data.frame
dat_tr <- trim_osmdata (dat, bb_sf)
bb_sp <- as (bb_sf, "Spatial")
class (bb_sp) # SpatialPolygonsDataFrame
dat_tr <- trim_osmdata (dat, bb_sp)

# Server-side trimming equivalent
bb <- getbb ("colchester uk", format_out = "osm_type_id")
query <- opq (bb) |>
    add_osm_feature (key = "highway")
dat <- osmdata_sf (query, quiet = FALSE)
} # }