title: Unexpected convertion output from Latlong to UTM in R
body: <p>I'm trying to convert Latlong to UTM but, for some reason, the results coming from R are very different from what I looking for.</p>
  
  <p>The dataset is just one observation (the city of São Paulo):</p>
  
  <p><strong>LatLong</strong></p>
  
  <p>Longitude of São Paulo: -46.633309</p>
  
  <p>Latitude of São Paulo: -23.550520</p>
  
  <p><strong>UTM coordinates (WGS84) of São Paulo</strong></p>
  
  <p>The UTM coordinates (WGS84) of São Paulo are: Zone 23K E: 333287.02 N: 7394586.09</p>
  
  <p>Source: <a href="http://www.gps-latitude-longitude.com/gps-coordinates-of-sao-paulo" rel="nofollow">http://www.gps-latitude-longitude.com/gps-coordinates-of-sao-paulo</a></p>
  
  <pre><code>library(rgdal)
  x&lt;-c(-46.633309)
  y&lt;-c(-23.550520)
  zone&lt;-23
  xy&lt;-data.frame(ID = 1:length(x), X = x, Y = y)
  coordinates(xy)&lt;-c("X", "Y")
  proj4string(xy)&lt;-CRS("+proj=longlat +datum=WGS84")  ## for example
  res&lt;-spTransform(xy, CRS(paste("+proj=utm +zone=",zone,"ellps=WGS84",sep='')))
  res
  
  &gt; res
           coordinates ID
  1 (333287, -2605414)  1 
  </code></pre>
  
  <p>Easting term seems to be right, but Northing is very diferent from the expected value (7394586.09 not equal to -2605414).</p>
  
  <p>Can anyone tell me what is going on?
  Thanks in advance.</p>