title: A* heuristic, overestimation/underestimation?
body: <p>I am confused about the terms overestimation/underestimation. I perfectly get how A* algorithm works, but i am unsure of the effects of having a heuristic that overestimate or underestimate.</p>
  
  <p>Is overestimation when you take the square of the direct birdview-line? And why would it make the algorithm incorrect? The same heuristic is used for all nodes.</p>
  
  <p>Is underestimation when you take the squareroot of the direct birdview-line? And why is the algorithm still correct?</p>
  
  <p>I can't find an article which explains it nice and clear so I hope someone here has a good description. </p>