Build shapes from simple feature object

Usage

create_shapes_from_sf(
  sf_shapes,
  gtfs,
  metric_crs = 3857,
  shape_dist_traveled = FALSE
)

Arguments

sf_shapes: sf object associating shape_id with an sf object (either LINESTRING or MULTILINESTRING).
gtfs: tidygtfs. GTFS feed.
metric_crs: numeric (Default 3857). EPSG code for a metric CRS used when computing distances (passed to multiline_to_sorted_linestring).
shape_dist_traveled: Boolean (Default FALSE). If TRUE, computes shape_dist_traveled for each generated shape.

Value

A data.table representing a GTFS shapes table. Includes shape_dist_traveled if shape_dist_traveled = TRUE.

Details

This function builds the shapes.txt file from a simple feature object.

It first converts any MULTILINESTRING geometries to LINESTRING geometries using the multiline_to_sorted_linestring, using a point guide per shape: all ordered stops when the selected trip is circular (first and last stop_id are equal), or the first two stops otherwise. Then, it converts the LINESTRING geometries to a data.table representing a GTFS shapes table using gtfstools::convert_sf_to_shapes.

Coordinates are 4326 (WGS 84) by default, following GTFS specifications.

Optionally, when shape_dist_traveled = TRUE, it estimates cumulative distance along each shape for all generated points and appends this as shape_dist_traveled. This metric is computed in the units of metric_crs, using GTFShift::project_points_along_geometry().

Examples

if (FALSE) { # \dontrun{
gtfs <- GTFShift::load_feed("gtfs.zip")
q <- opq("Lisbon") |>
    add_osm_feature(key = "route", value = c("bus", "tram")) |>
    add_osm_feature(key = "network", value = "Carris", key_exact = TRUE)

shapes_sf <- GTFShift::osm_shapes_to_routes(gtfs, q)

gtfs$shapes <- GTFShift::create_shapes_from_sf(shapes_sf, gtfs)
} # }