Hi,

I am trying (unsuccessfully) to migrate a formula (for calculating

distances between lat/lng positions) from JavaScript to Ruby:

//JavaScript:

dlng = p2_lng - p1_lng

dlat = p2_lat - p1_lat

a = (sin(dlat/2))^2 + cos(p1_lat) * cos(p2_lat) * (sin(dlon/2))^2

c = 2 * atan2( sqrt(a), sqrt(1-a) )

distance = R * c (where R is the radius of the Earth)

#Ruby:

dlng = p2_lng - p1_lng

dlat = p2_lat - p1_lat

a = (Math.sin(dlat/2))**2 + Math.cos(p1_lat) * Math.cos(p2_lat) *

(Math.sin(dlng/2))**2

c = 2 * Math.atan2( Math.sqrt(a), Math.sqrt(1-a) )

distance = 6373 * c #(radius of the Earth: 6373km

Any idea why the Ruby one returns incorrect numbers?

Ingo W.