title: Calculation of accumulation area
body: <p>I'm looking for a GIS/Geometric algorithm:</p>
  
  <p>I have 1000 points randomly distributed in a large area(such as a city), How can I find out all the small areas which have more than 15 points? Like this picture below:</p>
  
  <p><img src="https://i.stack.imgur.com/9yivv.png" alt="enter image description here"></p>
  
  <p>Each point has its own latitude and longitude coordinates. The small area less than 200m x 200m.</p>