NavList:

From: Nicolàs de Hilster <groups@dehilster.info>
Subject: [NavList 7061] Re: FW: [NavList 6952] Re: Chronometer Suggestions
To: NavList@navlist.net
Date: Thursday, January 15, 2009, 12:17 AM

On NavList 7052 Irv Haworth wrote:
> "I think it's well known that 1' of arc varies in length as a
function
> (cos)
> of the latitude."
>
>   
On which Gary LaPook replied in NavList 7053:
> That is true for one minute of longitude because parallels of latitude are
small circles.
> This is not true for one minute latitude of for any 
> other great circle. (Technically
 these also vary slightly due to the 
> oblateness of the earth but these small variations are ignored for
>  celestial navigation purposes.)
>   
For those who want to know how much exactly that variation is I posted 
attached graph of it in NavList 4750 on 24/03/2008.