[PROJ] Pseudo-mercator

[Andrew Patterson]

Even,

>  PROJ >= 6 is completely ignored with Mercator_1SP. With Mercator_1SP, the
> parameter that matters is the scale_factor. With Mercator_2SP, the one that
> matters is standard_parallel_1.  So it looks GDAL 2.4 interpreted somehow
> this latitude_of_center as the +lat_ts parameter, but I'd say this was an
> accident. This WKT is definitely weird.
>
 So this was extremely helpful. Just for laughs, I altered the WKT on that
map from Mercator_1SP -> Mercator_2SP and changed 'latitude_of_center' to
'standard_parallel_1' and now it works exactly as in the old GDAL & PROJ. I
take from this that there must have been some logic somewhere in the old
versions that saw 'Mercator_1SP' and 'latitude_of_center' and said "Ok, you
_clearly_ meant Mercator_2SP and 'standard_parallel_1', let me fix that for
you." If so, that suggests this must be somewhat common in existing maps. I
think one of my colleagues said we have something on the order of 5,000+
maps affected by this, but they're all from a Japanese vendor, so maybe
it's more common in certain parts of the world than others?

Either way, I can add this logic/hack to our app; if I see that combination
of parameters, I'll correct the WKT. For now, that will salvage the bulk of
the problematic maps, but we'll have to chase down the vendor to get them
to stop using that weird WKT.

Thank you very much!

> The name of the CONVERSION when exporting as WKT2 is only informational.
> It has no computational consequence. When importing a WKT1 string, PROJ
> will use "unnamed" as the CONVERSION name as the information isn't present.
>
Ah, OK. I'll pass that along to my colleague. He was perplexed by the
presence of the conversion. He's a GIS professional and could not figure
out what it was. This answer will probably ease his mind :)

Thanks again!
..............................
Andrew Patterson
Lead Software Architect
Avenza Systems Inc.

email: andrew at avenza.com
phone: 416.487.5116
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