Render shapefile with no projection in leaflet map

Question

I want to render a shapefile inside of a leaflet map.

This shapefile has no projection so I'm trying to give it one.

  directions <- readOGR("./directions/", "directions")
  proj4string(directions) <- CRS("+proj=longlat +datum=WGS84 +no_defs")

And after that I try to add it to my map like this:

  map <- leaflet() %>% 
    addProviderTiles("CartoDB.Positron") %>% 

    addPolygons(data=directions,weight=1,col = 'black') %>% 

    setView(lng = -3.8196207,
            lat = 40.4678698,
            zoom = 10)

The problem is that I get an error saying:

Geographical CRS given to non-conformant data: 450781.167295 4485221.863980

I tried using other projections as CRS like

  proj4string(directions) <- CRS("+proj=utm +zone=30 +ellps=GRS80 +units=m +no_defs")

which does not give me an error but the shapefile is not getting rendered either.

I don't really understand why that happens and how I can fix it.

BTW: I got this shapefile from a spanish website where traffic and airquality data gets published

Answer 1

You were very close. What you need to do is convert the projection from UTM Zone 17N to longitude and latitude projection.

library(sp)
library(rgdal)
library(leaflet)

# Read the shapefile
directions <- readOGR("directions", "directions")
# Set the projection to be UTM zone 30N
proj4string(directions) <- CRS("+proj=utm +zone=30 +ellps=GRS80 +units=m +no_defs")
# Conduct project transformation from UTM zone 30N to long-lat
directions_longlat <- spTransform(directions, CRS("+proj=longlat +datum=WGS84 +no_defs"))

map <- leaflet() %>% 
  addProviderTiles("CartoDB.Positron") %>% 
  addPolygons(data = directions_longlat, weight=1, col = 'black') %>% 
  setView(lng = -3.8196207,
          lat = 40.4678698,
          zoom = 10)
map