# https://stackoverflow.com/questions/47749078/how-to-put-a-geom-sf-produced-map-on-top-of-a-ggmap-produced-raster
library(ggplot2)
library(ggmap)
library(sf)
nc_map <- get_map("north carolina", maptype = "satellite", zoom = 6, source = "google")
st_crs(nc_map)
# Coordinate Reference System: NA
# assume the coordinate refence system is 3857
plot(st_transform(nc_shp, crs = 3857)[1], bgMap = nc_map)