[MapServer-dev] PROJECTION block strings and init=

Seth G sethg at geographika.co.uk
Thu Aug 24 03:52:17 PDT 2023

Hi all,

I just ran into an issue when using the following projection block returned "msProcessProjection(): Projection library error. proj error "Invalid value for an argument" for "init=esri:54052":


However using the following without the "init=" works:


This is confusing as "esri:54052" is in the proj.db, and for EPSG code both approaches work e.g. "init=epsg:4326" and "epsg:4326" are both fine. 

As noted in the PROJ docs [1] the "init=" PROJ strings were deprecated in PROJ6. 

So a couple of questions:

1. Should we update the msautotests and MapServer docs to remove  "init=" from PROJECTION blocks?
   However I think the "init=" needs to be kept to support custom projections not in proj.db as used in [2]
2. Should we consider having a minimum required version of PROJ for a future release of MapServer? This would allow backwards compatible code to be removed. 


[1] https://proj.org/en/9.2/development/migration.html#backward-incompatibilities
[2] https://github.com/MapServer/MapServer/pull/6795

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