Get trip geometry

Returns the geometry of each specified trip_id, based either on the shapes or the stop_times file (or both).

get_trip_geometry(gtfs, trip_id = NULL, file = NULL, crs = 4326)

Arguments

gtfs

A GTFS object, as created by read_gtfs().

trip_id

A character vector including the trip_ids to have their geometries generated. If NULL (the default), the function generates geometries for every trip_id in the GTFS.

file

A character vector specifying the file from which geometries should be generated (either one of or both shapes and stop_times). If NULL (the default), the function attemps to generate the geometries from both files, but only raises an error if none of the files exist.

crs

The CRS of the resulting object, either as an EPSG code or as an crs object. Defaults to 4326 (WGS 84).

Value

A LINESTRING sf.

Details

The geometry generation works differently for the two files. In the case of shapes, the shape as described in the text file is converted to an sf object. For stop_times the geometry is the result of linking subsequent stops along a straight line (stops' coordinates are retrieved from the stops file). Thus, the resolution of the geometry when generated with shapes tends to be much higher than when created with stop_times.

Examples

data_path <- system.file("extdata/spo_gtfs.zip", package = "gtfstools")

gtfs <- read_gtfs(data_path)

trip_geometry <- get_trip_geometry(gtfs)
head(trip_geometry)
#> Simple feature collection with 6 features and 2 fields
#> Geometry type: LINESTRING
#> Dimension:     XY
#> Bounding box:  xmin: -46.98404 ymin: -23.73644 xmax: -46.63535 ymax: -23.19474
#> Geodetic CRS:  WGS 84
#>      trip_id origin_file                       geometry
#> 1 CPTM L07-0      shapes LINESTRING (-46.63535 -23.5...
#> 2 CPTM L07-1      shapes LINESTRING (-46.87255 -23.1...
#> 3 CPTM L08-0      shapes LINESTRING (-46.64073 -23.5...
#> 4 CPTM L08-1      shapes LINESTRING (-46.98404 -23.5...
#> 5 CPTM L09-0      shapes LINESTRING (-46.77604 -23.5...
#> 6 CPTM L09-1      shapes LINESTRING (-46.69711 -23.7...

# the above is identical to
trip_geometry <- get_trip_geometry(gtfs, file = c("shapes", "stop_times"))
head(trip_geometry)
#> Simple feature collection with 6 features and 2 fields
#> Geometry type: LINESTRING
#> Dimension:     XY
#> Bounding box:  xmin: -46.98404 ymin: -23.73644 xmax: -46.63535 ymax: -23.19474
#> Geodetic CRS:  WGS 84
#>      trip_id origin_file                       geometry
#> 1 CPTM L07-0      shapes LINESTRING (-46.63535 -23.5...
#> 2 CPTM L07-1      shapes LINESTRING (-46.87255 -23.1...
#> 3 CPTM L08-0      shapes LINESTRING (-46.64073 -23.5...
#> 4 CPTM L08-1      shapes LINESTRING (-46.98404 -23.5...
#> 5 CPTM L09-0      shapes LINESTRING (-46.77604 -23.5...
#> 6 CPTM L09-1      shapes LINESTRING (-46.69711 -23.7...

trip_ids <- c("CPTM L07-0", "2002-10-0")
trip_geometry <- get_trip_geometry(gtfs, trip_id = trip_ids)
trip_geometry
#> Simple feature collection with 4 features and 2 fields
#> Geometry type: LINESTRING
#> Dimension:     XY
#> Bounding box:  xmin: -46.87255 ymin: -23.55262 xmax: -46.62922 ymax: -23.19474
#> Geodetic CRS:  WGS 84
#>      trip_id origin_file                       geometry
#> 1 CPTM L07-0      shapes LINESTRING (-46.63535 -23.5...
#> 2  2002-10-0      shapes LINESTRING (-46.62963 -23.5...
#> 3 CPTM L07-0  stop_times LINESTRING (-46.63544 -23.5...
#> 4  2002-10-0  stop_times LINESTRING (-46.62962 -23.5...
plot(trip_geometry["origin_file"])