[PROJ] open_license column in proj.db

[Even Rouault]

Hi Javier,

>
> Having a look at proj.db, I have seen a column in the table 
> "grid_alternatives" called "open_license"
> What is the purpose of this field? (apart from allowing a meaningless 
> "url")
> I guess it is not effectively used in the code.
>
It is reported as a metadata information in 
proj_grid_get_info_from_database(), so users can make an informed 
choice. It is used only for the following 2 grids which are publicly 
available but whose license terms are not considered open data:

('naptrans2008.gtx','','naptrans2008.gtx','GTX','geoid_like',0,NULL,'https://salsa.debian.org/debian-gis-team/proj-rdnap/raw/upstream/2008/naptrans2008.gtx',1,0,NULL),
('rdtrans2008.gsb','','rdtrans2008.gsb','NTv2','hgridshift',0,NULL,'https://salsa.debian.org/debian-gis-team/proj-rdnap/raw/upstream/2008/rdtrans2008.gsb',1,0,NULL),
('netherlands/rdtrans2008','','rdtrans2008.gsb','NTv2','hgridshift',0,NULL,'https://salsa.debian.org/debian-gis-team/proj-rdnap/raw/upstream/2008/rdtrans2008.gsb',1,0,NULL),

> The three entries with this field to "0" are a bit redundant, right?

No I don't think so. There are 2 different grids. And the rdtrans2008 
one has a different name if it is used by EPSG records or ESRI records, 
hence 2 records for it as original_grid_name is the key.


> "original_grid_name" and "old_proj_grid_name" are the same. Are those 
> entries needed?

There are tons of records where they are different like:

INSERT INTO grid_alternatives(original_grid_name,
                               proj_grid_name,
                               old_proj_grid_name,
                               proj_grid_format,
                               proj_method,
                               inverse_direction,
                               package_name,
                               url, direct_download, open_license, 
directory)
                       VALUES ('conus.las',
                               'us_noaa_conus.tif',
                               'conus',
                               'GTiff',
                               'hgridshift',
                               0,
                               NULL,
'https://cdn.proj.org/us_noaa_conus.tif', 1, 1, NULL);


old_proj_grid_name corresponds to known grid names by PROJ before PROJ 7 
and the migration to GeoTIFF, so NTv2, CTable2 and GTX files

original_grid_name corresponds to the """"official"""" name in the 
registry imported by PROJ, so most of the time the one used by EPSG (and 
a few ones from ESRI or IGNF)

Even


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