Getting started with geographical coordinates

[Ralph DiMola]

A friend of mine turned me on to this 10 years ago. This is the Haversine
formula. It assumes that the earth is sphere and is not very accurate for
very small distances. I have not tried to use the Vincenty's formula that
does better. For general purposes the HF should be sufficient.

Just give me the credit for LC implementation of a friends of mines routine.
Although I understand how it works the real credit goes to Don Josef de
Mendoza y Rios in 1796.

The girls and boys doing math in that period really set the stage. This
brought me back to my CGI days when I was patting myself on the back when I
self learned(with a friends help after reading the Kreyszig) how to move
points in space and calculate lighting.  I then self reflected and realized
that I was just putting together the pieces of math that these folks created
out of thin air. I still felt like I accomplished something but very much
smaller the scheme of things.

Ralph DiMola
IT Director
Evergreen Information Services
rdimola at evergreeninfo.net

-----Original Message-----
From: use-livecode [mailto:use-livecode-bounces at lists.runrev.com] On Behalf
Of Bob Sneidar via use-livecode
Sent: Friday, April 03, 2020 5:31 PM
To: How to use LiveCode
Cc: Bob Sneidar
Subject: Re: 

Ralph, this is brilliant. I remember trying to do something similar years
ago, and giving up because I didn't know how to do the math. I suck at math,
or rather I am too lazy and impatient to work the problem. 

Bob S

> On Apr 3, 2020, at 14:27 , Ralph DiMola via use-livecode
<use-livecode at lists.runrev.com> wrote:
> 
> Graham,
> 
> This my distance calculation for what it's worth.
> 
> Function distance lat1, lon1, lat2, lon2, unit
>   -- Calculate Distance between to points
>   --
>   --lat1, lon1, lat2, lon2 are in deg.fractionalDegrees
>   -- Unit
>   --     if empty then miles
>   --     K = kilometers
>   --     N = nautical miles
>   local theta
>   local dist
> 
>   Put lon1 - lon2 into theta
>   put Sin(deg2rad(lat1)) * Sin(deg2rad(lat2)) + Cos(deg2rad(lat1)) *
Cos(deg2rad(lat2)) * Cos(deg2rad(theta)) into dist
> 
>   put Acos(dist) into dist
>   put rad2deg(dist) into dist
>   put dist * 60 * 1.1515 into dist
> 
>   switch unit
>      case "K"
>         put dist * 1.609344 into dist
>      case "N"
>         put dist * 0.8684 into dist
>   end switch
> 
>   Return dist
> 
> End distance
> 
> 
> Function rad2deg rad
>   Return rad / PI * 180.0
> end rad2deg
> 
> 
> Ralph DiMola
> IT Director
> Evergreen Information Services
> rdimola at evergreeninfo.net


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