Project spatial points on a spatial network

Usage

st_project_on_network(x, network, on = "edges")

Arguments

x: The spatial features to be projected, either as object of class sf or sfc, with POINT geometries.
network: An object of class sfnetwork.
on: On what component of the network should the points be projected? Setting it to 'edges' (the default) will find the nearest point on the nearest edge to each point in x. Setting it to 'nodes' will find the nearest node to each point in x.

Value

The same object as x but with its geometries replaced by the projections.

Details

This function uses st_nearest_feature to find the nearest edge or node to each feature in x. When projecting on edges, it then finds the nearest point on the nearest edge by calling st_nearest_points in a pairwise manner.

Note

Due to internal rounding of rational numbers, even a point projected on an edge may not be evaluated as actually intersecting that edge when calling st_intersects.

Examples

library(sf, quietly = TRUE)

oldpar = par(no.readonly = TRUE)
par(mar = c(1,1,1,1))

# Create a spatial network.
n1 = st_point(c(0, 0))
n2 = st_point(c(1, 0))
n3 = st_point(c(2, 0))

e1 = st_sfc(st_linestring(c(n1, n2)), crs = 3857)
e2 = st_sfc(st_linestring(c(n2, n3)), crs = 3857)

net = as_sfnetwork(c(e1, e2))

# Create spatial points to project in.
p1 = st_sfc(st_point(c(0.25, 0.1)))
p2 = st_sfc(st_point(c(1, 0.2)))
p3 = st_sfc(st_point(c(1.75, 0.15)))

pts = st_sf(foo = letters[1:3], geometry = c(p1, p2, p3), crs = 3857)

# Project points to the edges of the network.
p1 = st_project_on_network(pts, net)

plot(net)
plot(st_geometry(pts), pch = 20, col = "orange", add = TRUE)
plot(st_geometry(p1), pch = 4, col = "orange", add = TRUE)


# Project points to the nodes of the network.
p2 = st_project_on_network(pts, net, on = "nodes")

plot(net)
plot(st_geometry(pts), pch = 20, col = "orange", add = TRUE)
plot(st_geometry(p2), pch = 4, col = "orange", add = TRUE)


par(oldpar)