title: I tried all ways, but still my area is calculated wrongly in Postgis
body: <p>I created a very simple polygon in the middle of Germany to demonstrate my problem.</p>
  
  <p>You can visualize it in geojsonlint using the following GeoJSON</p>
  
  <pre><code>{"type":"Polygon","coordinates":[[
  [10.439844131469727,51.17460781257472],
  [10.430574417114258,51.1753073564544],
  [10.429565906524658,51.17179607723465],
  [10.438792705535889,51.170706315523866],
  [10.439372062683105,51.17267055874809],
  [10.43975830078125,51.17439256616884],
  [10.439844131469727,51.17460781257472]]]G}
  </code></pre>
  
  <p>When calculating the surface with online tools (e.g. <a href="http://www.daftlogic.com/projects-google-maps-area-calculator-tool.htm" rel="nofollow">http://www.daftlogic.com/projects-google-maps-area-calculator-tool.htm</a>, but I tried several),
  I get the following numbers (these are based on a similar drawing of the polygon, but not the exact same one, as I couldn't copy it over to these tools):</p>
  
  <ul>
  <li>276583.39 m²</li>
  <li>0.28 km²</li>
  <li>68.35 acres</li>
  <li>27.66 hectares</li>
  <li>2977118.86 feet²</li>
  <li>0.08 square nautical miles</li>
  </ul>
  
  <p>Now I want to calculate these areas using POSTGIS, but I always get wrong and not matching numbers.</p>
  
  <p>First I started without transformation using the examples given here:</p>
  
  <p><a href="http://postgis.net/docs/ST_Area.html" rel="nofollow">http://postgis.net/docs/ST_Area.html</a></p>
  
  <pre><code> SELECT ST_Area(the_geom) As sqft, ST_Area(the_geom)*POWER(0.3048,2) As sqm
   FROM (SELECT ST_GeomFromText('
   POLYGON ((51.17460781257472  10.439844131469727,
   51.1753073564544 10.430574417114258, 
   51.17179607723465 10.429565906524658,
   51.170706315523866 10.438792705535889,
   51.17267055874809 0.439372062683105,
   51.17439256616884 10.43975830078125,
   51.17460781257472 10.439844131469727))',4326) ) As foo(the_geom);
  </code></pre>
  
  <p>--> sqft = 3.52643124351653e-05 and sqm = 3.27616182873666e-06</p>
  
  <p>How can I interprete these numbers?
  Then I tried to transform it to WGS 84 / UTM zone 33N 32633</p>
  
  <pre><code>SELECT ST_Area(the_geom) As sqft, ST_Area(the_geom)*POWER(0.3048,2) As sqm
  FROM (SELECT ST_Transform(ST_GeomFromText('
  POLYGON ((51.174661624019286 10.440187454223633,
  51.17067940750161 10.438899993896484,
  51.17197097486416 10.429544448852539, 
  51.17536116708255 10.430488586425781,
  51.174661624019286 10.440187454223633))',4326),32633) ) As foo(the_geom);
  </code></pre>
  
  <p>--> sqft = 662918.939349234 and sqm = 61587.1847391195</p>
  
  <p>But even these numbers don't come close.</p>