From: chiaro scuro <kiaroskuro@...>
Date: 2006-04-27T19:21:53+09:00
Subject: Re: Trouble migrating formula from JavaScript to Ruby

is it possible that you need to make numbers explicitly float? eg: 2 --> 2.0

On 4/27/06, Ingo Weiss <ingoweiss@gmail.com> wrote:
> 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 Weiss
>
> --
> Posted via http://www.ruby-forum.com/.
>
>


--
Chiaroscuro
---
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