[Proj] A template for documenting projections
Clifford J Mugnier
cjmce at lsu.edu
Thu Sep 8 18:47:22 EST 2016
There's a whopping difference between pure projection parameter definitions and large-scale mapping GRID parameters. e.g., False Northing South of False Origin, etc. which is found in several nations of North Africa. Similar esoterica occur worldwide. I recommend separating the two. Novices do not need to be confronted with exquisite parameters to "fill-in the blanks.
Sent from Cliff Mugnier's iPhone
> On Sep 8, 2016, at 6:29 PM, Kristian Evers <kreve at sdfe.dk> wrote:
> I think the generic parameters like false easting/northing should be documented elsewhere.
> In fact they already are on http://proj4.org/parameters.html although that page could use some more work.
> Yes, you are absolutely right about the +k_0 and +lat_ts options!
> Fra: Even Rouault [even.rouault at spatialys.com]
> Sendt: 9. september 2016 00:32
> Til: proj at lists.maptools.org
> Cc: Kristian Evers
> Emne: Re: [Proj] A template for documenting projections
> Le jeudi 08 septembre 2016 23:50:09, Kristian Evers a écrit :
>> 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.
>> 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) :
> Spatialys - Geospatial professional services
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