I have some data that exist in a waterway system river network, and I'm trying to draw a buffer around some points, to see which areas of the water lie within a 10km boat ride.
library(raster)
library(ggplot2)
canada <- raster::getData("GADM",country="CAN",level=1)
canada_prov = canada[canada$NAME_1 == "British Columbia"] # subset to just BC
location <- data.frame(
name = c("one", "two"),
lat = c(52.79883, 52.53555),
long = c(-128.3144, -128.3593)
)
ggplot2::ggplot() +
geom_polygon(data = canada_prov,
aes(x = long, y = lat, group = group),
colour = "black",
linewidth = 0.01,
fill = "grey65") +
geom_point(data = location,
aes(x = long, y = lat), shape = 21, fill = "red", size = 3) +
coord_cartesian(xlim = c(-128.6, -128.2), ylim = c(52.4, 52.95)) +
theme_bw() +
labs(x = "Longitude (°)", y = "Latitude (°)")
Here the dark gray colour is land and the white is water. What I want to do is create a buffer around these points that shows everywhere I could get in these waterways if I drove a boat for 10km.
The reason I'm having trouble is I know I can create a single circular buffer around these points, but I need the edge of the buffer polygon to respect the restrictions of the land/water divide. I also don't want the buffer to just do a straight-line distance of 10km to everywhere in the waterways.
Is there a way I can go about this? I haven't found anything in sf or raster packages yet that seems to be what I'm looking for?
Ideally what I would end up with is something that looks like this crappy hand-drawn version here:
As always any help appreciated!!
