Major Description
For tree traversals and edge cases we still sometimes invoke full haversin (with asin() call and everything). this is not necessary: we just need to compute the exact sort key needed for comparisons.
While not a huge optimization, its obviously less work and keeps the overhead of the BKD traversal as low as possible. And it removes the slow asin call from any hot path (its already done for sorting too), with its large tables and so on.