[Proj] A template for documenting projections

Even Rouault even.rouault at spatialys.com
Thu Sep 8 17:32:23 EST 2016

Le jeudi 08 septembre 2016 23:50:09, Kristian Evers a écrit :
> All,
> I have spend a few hours documenting the Mercator projection in the hopes
> that it can serve as a template for the rest of the projections that still
> need to be documented.
> http://proj4.org/projections/merc.html
> This is just my first initial thoughts on how to document a projection.
> I've divided the page into a few sections:
> - A short introduction
> - A table with a few key facts
> - Plot(s)
> - Usage/examples
> - Underlying math
> - References
> I would like to hear your thought on this. Is this a sufficient level of
> documentation? Did I leave out something obvious (in general terms, not
> specific to the Mercator projection)? Do you like the general format?


Looks good !

What about documenting the false easting x_0, false northing y_0 parameters ? 
But as those ones apply for all projections since they are applied in the 
generic code of pj_fwd/pj_inv, they should perhaps be documented in a general 
page. The same applies for the central meridian (lon_0).

Regarding Mercator, proj actually supports 2 forms, the one with +lat_ts 
(Mercator_2SP) and the one with the scale factor +k_0 (Mercator_1SP)
I found this with libgeotiff projection catalog, which might be a useful 
resource (the original URL is defunct since a few days, hence this wayback 
machine URL) :


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