I rely on haversine distance quite a bit and feel sort of disappointed in myself that I never really looked up the background on it before now

But first everyone must agree on the radius of the earth!

And if the distances are known to be small it may be quicker to calculate the chord length.

Bada bing, bada boom. I used to work with GIS data quite frequently, and I probably used this at least once a week at the time.

Yes, I used the haversine formula just a few weeks ago.