title: OpenLayers3 multipolygon.getArea returns greater than expected values
body: <p>I'm giving my first steps with OpenLayers3, and I'm getting somewhat strange results when trying to obtain the area of a selected feature.</p>
  
  <p>I've a map who loads a vector layer from a KML source.
  On those KML there are several features represented as multipolygons which represents the borders of some north Spain's regions.</p>
  
  <p>When I select the features, they change correctly it's styles according to my code, but when I try to retrieve it's area through multipolygons.getArea I obtain values a lot bigger than expected (almost double).</p>
  
  <p>My map code:
      
      </p>
  
  <pre><code>&lt;div id="map" class="map" style="width:100%; height:600px;"&gt;&lt;/div&gt;
  &lt;script type="text/javascript"&gt;
  
    var projection = new ol.proj.get("EPSG:3857");
  
    var mapa = new ol.layer.Tile({
      source: new ol.source.MapQuest({ layer: 'osm' })
    });
  
    var kmlLayer = new ol.layer.Vector({
      source: new ol.source.KML({
        projection: projection,
        url: "/Content/Documents/CCAA.txt",
        extractStyles: false
      })
    });
  
    var select = new ol.interaction.Select({
      condition: ol.events.condition.click,
      style: new ol.style.Style({
        fill: new ol.style.Fill({
          color: "rgba(0, 255, 0, 0.5)"
        }),
        stroke: new ol.style.Stroke({
          color: "#000000",
          width: 2
        })
      })
    });
  
    var map = new ol.Map({
      interactions: new ol.interaction.defaults().extend([select]),
      target: 'map',
      layers: [ mapa, kmlLayer ],
      view: new ol.View({
        center: [-426970.8463461736, 5299807.853963373],
        projection: projection,
        zoom: 7
      })
    });
  
    select.on('select', function (e) {
      var feature = e.selected[0];
      console.log(feature.getGeometry().getArea());
    });
  
    map.addControl(new ol.control.ScaleLine());
  
  &lt;/script&gt;
  </code></pre>
  
  <p>And this is an example of the KML data:</p>
  
  <pre><code>&lt;Placemark&gt;
   &lt;MultiGeometry&gt;
    &lt;Polygon&gt;
      &lt;outerBoundaryIs&gt;
        &lt;LinearRing&gt;
          &lt;coordinates&gt;
            -4.57486104965204,43.4001388549807,0 
            .....
          &lt;/coordinates&gt;
        &lt;/LinearRing&gt;
      &lt;/outerBoundaryIs&gt;
    &lt;/Polygon&gt;
  &lt;/Multigeometry&gt;
  &lt;/Placemark&gt;
  </code></pre>
  
  <p>The getArea of this multipolygon is returning 20021810258.82251 (I assume square meters as I'm using Mercator Projection), while the expected result would be about 10000 square km.</p>
  
  <p>I'm aware of the difficulties and problems with projections to a plane, and I was expecting a rough area result, but I'm getting twice the value I expected... it seems too much for a problem with projections or calculation... so I think there's something I'm missing here.</p>
  
  <p>Any insight on the matter will be much appreciated.</p>