From: "Peña, Botp" <botp@...>
Date: 2006-04-27T19:20:33+09:00
Subject: Re: Trouble migrating formula from JavaScript to Ruby

Ingo Weiss:

# //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?

1) can you post sample running codes on both? (eg what are the values of p2_lang, etc)

2) do you have test cases? (so we know what to expect)

kind regards -botp