Shapefile and location coordinates don't overlap each other

I am trying to overlay a map of country with pointers on specific locations. For this I first downloaded the boundary of country and then the lat/lon values of the points I want to plot

library(rgeoboundaries)
boundary <- geoboundaries("Mongolia")

library(MODIStools)
points <- mt_sites() %>%
  filter(country == "Mongolia")

Then I tried to plot them together using ggplot2 but they dont overlay on each other.

library(ggplot2)
ggplot() +
  geom_sf(data = boundary) +
  geom_point(data = points,
             aes(x = latitude,
                 y = longitude))

enter image description here

1 answer

  • answered 2021-04-08 07:04 Bappa Das

    Your points is a data.frame not a SpatialPointsDataFrame. So, first I have converted the data.frame to SpatialPointsDataFrame using coordinates(points) <- ~longitude + latitude. Then I have assigned it a crs (+proj=longlat +datum=WGS84 +no_defs). Then I have converted the sp object to sf object using st_as_sf and then I have plotted it like

    library(rgeoboundaries)
    library(raster)
    library(tidyverse)
    library(sf)
    library(MODISTools)
    
    boundary <- geoboundaries("Mongolia")
    
    points <- mt_sites() %>%
      filter(country == "Mongolia")
    
    #Check the coordinate reference of points and boundary
    crs(points)
    #> [1] NA
    crs(boundary)
    #> CRS arguments: +proj=longlat +datum=WGS84 +no_defs 
    
    #See the class of the points
    class(points)
    #> [1] "data.frame"
    
    #Convert the data.frame to SpatialPointsDataFrame
    coordinates(points) <- ~longitude + latitude
    
    #Assign the crs to points SpatialPointsDataFrame
    crs(points) <- crs(boundary)
    
    #Convert sp object to sf object
    points_sf <- st_as_sf(points)
    
    #Plot the results
    ggplot() +
      geom_sf(data = boundary) +
      geom_sf(data = points_sf)
    

    enter image description here