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Adds Pseudo Mercator to build_db_from_iau.py#3645

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rouault merged 2 commits intoOSGeo:masterfrom
AndrewAnnex:add_mercator_to_build_db_from_iau.py
Apr 7, 2023
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Adds Pseudo Mercator to build_db_from_iau.py#3645
rouault merged 2 commits intoOSGeo:masterfrom
AndrewAnnex:add_mercator_to_build_db_from_iau.py

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@AndrewAnnex
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Note there is some inconsistency with hyphenation of "Pseudo-Mercator" so this may need a double check, but I believe what I have is consistent with EPSG:3857 WKT2:2019 representation. Related to pdssp/csvforwkt#5

  • Added clear title that can be used to generate release notes

Note there is some inconsistency with hyphenation of "Pseudo-Mercator"
so this may need a double check, but I believe what I have is consistent
with EPSG:3857 WKT2:2019 representation.
@rouault
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rouault commented Mar 6, 2023

Settting it as a draft seeing remark from @thareUSGS in pdssp/csvforwkt#4 (comment). In particular the XXXX90 code needs to be confirmed for interoperability with other implementations

@rouault rouault marked this pull request as draft March 6, 2023 09:41
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@AndrewAnnex Why "Popular Visualization Pseudo Mercator" (EPSG: 1024) and not simply "Mercator (Spherical)" (EPSG: 1026). https://epsg.io/1026-method

I have never fully understood the whole Mercator / Web Mercator issue. I would rather use a name that isn't so odd (e.g., "Popular Visualization...") if possible. Looks like it is the same equation used in Mercator (Spherical).

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rouault commented Mar 6, 2023

Looks like it is the same equation used in Mercator (Spherical).

There's a subtlety if it is applied on a non-spherical ellipsoid. EPSG:1024 will always use the semi-major axis as the R value, whereas EPSG:1026 will use the radius of the conformal sphere, at the latitude of origin, which will be a * sqrt(1 - e^2) for latitude of origin = 0

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@rouault thanks for that explanation, I hope that 1024 is the best choice of "mercator" in order to make it slightly more straight forward to adapt/extend standards and front ends that assume 3857 for Earth, so that the correct semi-major axis can just be swapped in.

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@rouault This update for "Web Mercator" has been approved and merged. pdssp/csvforwkt#5 It would be great to see this pull request also approved for PROJ. thanks!

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3 participants