[MapServer-users] Switch custom projection from PROJ 7 to PROJ 9 (from flat epsg file to aux database)

[Michal Seidl]

Hello,
after some more deep reading and searching I have found, probably not 
perfect but working solution. If I understand situation main problems are:

- Mapserver itself makes in some cases some preprocessing before calling 
PROJ API mainly it changes <AUTH>:<CODE> to init=<AUTH>:<CODE>

- PROJ 9.x carries differently <AUTH>:<CODE> and init=<AUTH>:<CODE> and 
init=<AUTH>:<CODE> is really deprecated and in some situation forbidden

- PROJ 9.x looks for EPSG:<code> always in main proj.db so aux.db does 
not help

So the solution is:
- copy original proj.db into some user location
- set this location with PROJ_DATA in /etc/mapserver.conf
- create alias for EPSG:5514 as EPSG:102067 in proj.db with following SQL

INSERT INTO projected_crs
(
  auth_name,
  code,
  name,
  description,
  coordinate_system_auth_name,
  coordinate_system_code,
  geodetic_crs_auth_name,
  geodetic_crs_code,
  conversion_auth_name,
  conversion_code,
  text_definition,
  deprecated
)
SELECT
  'EPSG',
  '102067',
  'Legacy EPSG:102067 Krovak',
  description,
  coordinate_system_auth_name,
  coordinate_system_code,
  geodetic_crs_auth_name,
  geodetic_crs_code,
  conversion_auth_name,
  conversion_code,
  NULL,
  0
FROM projected_crs
WHERE auth_name='EPSG'
AND code='5514';


Best regards Michal S.