[Proj] Lambert Conformal Conic

[OvV_HN]

----- Original Message ----- 
From: "Gerald I. Evenden" <geraldi.evenden at gmail.com>
To: "PROJ.4 and general Projections Discussions" <proj at lists.maptools.org>
Sent: Sunday, April 26, 2009 4:57 PM
Subject: Re: [Proj] Lambert Conformal Conic


> On Sunday 26 April 2009 7:41:44 am OvV_HN wrote:
>> There are more disturbing differences with respect to the Lambert
>> projection.
>> ....
>> The Belgian example at hand reads:
>>
>> Lambert 1972 projection
>> lat = 50d 40m 46.461s N; lon = 5d 48m 26.533s E;
>> Published grid coordinates: X = 251763.204; Y = 153034.174 m
>> With the published projection constants
>
> Question: where do these constants come from and/or what do they mean?
>
> I am not aware of making conic specifications in this manner.

Now you are. I think it's a filthy habit, developed in a time when CPU time 
was at a premium.
People calculated probably with a hand calculator the projection variables 
that are not varying for a given application.
I would like to refer to the EPSG Guidance note G7-2, specifically the 
formulae of paragraph 1.3.1.1 of the Jan 2009 version (EPSG dataset 
coordinate operation method code 9802).
Constant p in my email is the same as constant n in the EPSG Guidance note 
G7-2 and constant k is the same as a*F in the same publication.

Oscar van Vlijmen