title: OpenCV detect partial circle with noise
body: <p>I have tried to use OpenCV HoughCircles and findContours to detect a circle however the circle isn't complete enough or there is too much noise in the image for these algorithms.  Or perhaps we are just not familiar enough with the OpenCV.  Attached is my image that I need to find the circle on.  You should be able to see it clearly with your eyes however, none of the circle detection algorithms seem to work.  I have found that applying a median filter cleans up most of the noise but even after median filtering the algorithms can't detect the circle.</p>
  <p>Note I even looked at and tried the solution here so it is not a duplicate of that question:
  <a href="https://stackoverflow.com/questions/20698613/detect-semi-circle-in-opencv">Detect semicircle in OpenCV</a></p>
  <p>Any ideas?  This is my source image that I need to use.</p>
  <p>Also, the reason I want to detect the circle is I want to do a calculation using only the points that are a part of the circle.</p>
  <p>Original Image:
  <a href="http://www.collegemobile.com/IMG_2021.JPG" rel="nofollow noreferrer">http://www.collegemobile.com/IMG_2021.JPG</a></p>
  <p>Median Filtered Image:
  <a href="http://www.collegemobile.com/IMG_2022.JPG" rel="nofollow noreferrer">http://www.collegemobile.com/IMG_2022.JPG</a></p>