[Proj] Cosmetic latitudes, and the diacritics of Josef Krovak and others

strebe at aol.com strebe at aol.com
Mon Mar 23 12:59:21 EST 2009


daan wrote (about a central latitude that doesn't affect the shape of the 

> Snyder includes it explicitly in his formulations, referring 
> to it as the "latitude of origin" and denoting it as φ₀.

Yes, now that you mention it. I have never noticed it before, but Snyder 
uses phi_0 when the parameter does not affect the projection shape, but 
otherwise he uses phi_1 (which he often calls the "latitude of the center of 
the projection and origin"), or else phi_1 and phi_2 for two standard parallels.  

This convention is, in fact, stated in his list of symbols on pages viii - ix, 
which I hadn't read carefully enough before.  

"Latitude of origin" sounds fine, but I am not too fond of using 
many different names for what is called lat_0 in Proj.4.  The 
EPSG Guidance Note 7.2 has gone too far in this direction, I think. 
I like "central latitude" as the only name.



Please note also that "Latitude of origin" is the  name in the Well Known Text format specification.


— daan Strebe

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