Projects points to linear distances along a route shape. — project_onto

This function takes spatial points and projects them onto a route, returning the linear distance from the beginning terminal of the route.

Usage

project_onto_route(
  shape_geometry,
  points,
  original_crs = 4326,
  project_crs = 4326
)

Arguments

shape_geometry: The SF object to project onto. Must include the field shape_id. See get_shape_geometry().
points: Can be either: a dataframe representing point coordinates, with fields longitude and latitude; or, an SF or SFC point object.
original_crs: Optional. A numeric EPSG identifier. If a dataframe is provided for points, this will be used to define the coordinate system of the longitude / latitude values. Default is 4326 (WGS 84 ellipsoid).
project_crs: Optional. A numeric EPSG identifer indicating the coordinate system to use for spatial calculations. Consider setting to a Euclidian projection, such as the appropriate UTM zone. Default is 4326 (WGS 84 ellipsoid).

Value

The points input (either dataframe or SF) with an appended column for the linear distance along the route. If points is an SFC, a vector of numeric distances is returned. Units are those of the spatial projection used (e.g., meters if using UTM).

Examples

# Set my parameters
my_crs <- 32618

# Get shape data
c53_shape <- new_transittraj_data("get_shape_geometry")

# Set points of interest
my_points <- data.frame(longitude = c(-76.990038, -77.036289),
                        latitude = c(38.871335, 38.917054),
                        poi_name = c("11th St Bridge", "16th & U"))

# Run project_onto_route
my_points_proj <- project_onto_route(shape_geometry = c53_shape,
                                     points = my_points,
                                     project_crs = my_crs)
head(my_points_proj)
#>   longitude latitude       poi_name  distance
#> 1 -76.99004 38.87134 11th St Bridge  5422.615
#> 2 -77.03629 38.91705       16th & U 13402.281