[Proj] Convergence

[Kees Krikke]

Thanks Charles for your clarification. So i suppose that proj's
convergence calculation for lcc is not correct. I will try to submit a
bug report for this.

Regards,

Kees krikke

On 9/17/2008, "Charles Karney" <ckarney at sarnoff.com> wrote:

>I believe the convention is:
>
>    meridian convergence = bearing of grid north (measured clockwise
>    	     		   from true north)
>
>This is the sign convention suggested by those little figures at the
>bottom of large scale maps (USGS and UKOS for example) which indicate
>the bearing of magnetic and grid north relative to true north.  (And the
>universal convention is, I believe, that "bearings" are measured
>clockwise.)
>
>This is consistent with
>
>http://www.lantmateriet.se/templates/LMV_Meridiankonvergens.aspx?id=11496&lang=EN
>
>The UK OS page
>
>http://www.ordnancesurvey.co.uk/oswebsite/gps/information/coordinatesystemsinfo/guidetonationalgrid/page19.html
>
>seems to have it backward.  However, the previous page
>
>
>http://www.ordnancesurvey.co.uk/oswebsite/gps/information/coordinatesystemsinfo/guidetonationalgrid/page18.html
>
>says
>
>    true bearing = grid bearing + convergence
>
>which is consistent with the convention (assuming bearing are always
>measured clockwise from the reference direction).
>
>--
>Charles Karney <ckarney at sarnoff.com>
>Sarnoff Corporation, Princeton, NJ 08543-5300
>
>URL: http://charles.karney.info
>Tel: +1 609 734 2312
>Fax: +1 609 734 2662
>
>