title: Good algorithm for finding subsets of point sets
body: <p>I'm trying to find suitable algorithms for searching subsets of 2D points in larger set.
  A picture is worth thousand words, so:</p>
  
  <p><img src="https://i.stack.imgur.com/OkBa4.png" alt="enter image description here"></p>
  
  <p>Any ideas on how one could achieve this? Note that the transformations are just rotation and scaling.</p>
  
  <p>It seems that the most closely problem is <em>Point set registration</em> [1].
  I was experimenting with CPD and other rigid and non-rigid algorithms' implementations, but they don't seem to perform
  too well on finding small subsets in larger sets of points.</p>
  
  <p>Another approach could be using star tracking algorithms like the <em>Angle method</em> mentioned in [2]
  or more robust methods like [3]. But again, they all seem to be meant for large input sets and target sets. I'm looking for something less reliable but more minimalistic...</p>
  
  <p>Thanks for any ideas!</p>
  
  <p>[1]: <a href="http://en.wikipedia.org/wiki/Point_set_registration" rel="noreferrer">http://en.wikipedia.org/wiki/Point_set_registration</a></p>
  
  <p>[2]: <a href="http://www.acsu.buffalo.edu/~johnc/star_gnc04.pdf" rel="noreferrer">http://www.acsu.buffalo.edu/~johnc/star_gnc04.pdf</a></p>
  
  <p>[3]: <a href="http://arxiv.org/abs/0910.2233" rel="noreferrer">http://arxiv.org/abs/0910.2233</a></p>