[Proj] Convergence

[Gerald I. Evenden]

Something does appear to be broken.  

To fix: comment out the last assignment statement in the file proj_lcc.c.

P->spc = fac;

to

/* P->spc = fac; */

This forces the software to do numerical estimation of scale, blah, blah 
rather than use the analytic equations within lcc.

At the moment, I do no know whether the procedure that calls fac or fac itself 
is the problem but something is broken in more ways than just the 
convergence.

Recompile and link.


On Monday 22 September 2008 5:04:18 am Kees Krikke wrote:
> 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/coordinatesystem
> >sinfo/guidetonationalgrid/page19.html
> >
> >seems to have it backward.  However, the previous page
> >
> >
> >http://www.ordnancesurvey.co.uk/oswebsite/gps/information/coordinatesystem
> >sinfo/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
>
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