title: Polar/Stereographic map in R
body: <p>I am trying to produce a sterographic map similarly to this:</p>
  
  <p><a href="https://i.stack.imgur.com/kU3U8.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/kU3U8.png" alt="enter image description here"></a></p>
  
  <p>What I am trying to do is to add:</p>
  
  <ol>
  <li>Coordinates</li>
  <li>Graticule lines</li>
  </ol>
  
  <p>This can be in both base R or with ggplot2. Any help is appreciated.</p>
  
  <p><strong>My attempts so far</strong></p>
  
  <pre><code>library(rgdal)
  library(raster)                                                                                                     
  
  proj &lt;- "+proj=stere +lat_0=90 +lat_ts=70 +lon_0=-45 +k=1 +x_0=0 +y_0=0 +a=6378273 +b=6356889.449 +units=m +no_defs"
  
  data("wrld_simpl", package = "maptools")                                                                            
  wm &lt;- crop(wrld_simpl, extent(-180, 180, 45, 90))                                                                   
  plot(wm)                                                                                                            
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/yMJS0.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/yMJS0.png" alt="enter image description here"></a></p>
  
  <pre><code>wm &lt;- spTransform(wm, CRSobj = CRS(proj))
  plot(wm)
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/dVkeI.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/dVkeI.png" alt="enter image description here"></a></p>