[dagw]

You're missing another potentially really important part in the comment. Why you chose to use the Haversine distance formula. Since you seem to be calculating the distance between two points on Earth it would be really useful to have a comment like

  // Vincenty algorithm too slow for our use case 
  // and we don't need that level of accuracy.

to make it clear that using Haversine was a conscious choice rather than the first answer you saw on the first question you looked at on Stack Overflow :)