title: C# GMap.Net calculate surface of polygon
body: <p>I am searching for a way to calculate the surface under a polygon.</p>
  
  <p>The thing I want to accomplish is that a user that uses my program, can create a polygon to mark out his property. Now I want to know what the surface area is so I can tell the user how big his property is.</p>
  
  <p>Unit m² or km² or hectare.</p>
  
  <p>The points of the polygon have a latitude and longitude.</p>
  
  <p>I am using C# with WPF and GMap.NET. The map is in a <code>WindowsFormHost</code> so I can use the Winforms thing from GMap.Net because this provoides overlays etc.</p>
  
  <p>I hope that someone can help me or show me a post where this is explained that I didn't found.</p>