[Qgis-developer] SRS DB maintenance

[Radim Blazek]

On Mon, Jun 3, 2013 at 4:48 PM, Jürgen E. <jef at norbit.de> wrote:
> Hi Radim,
>
> On Mon, 03. Jun 2013 at 13:10:21 +0200, Radim Blazek wrote:
>> If I got it, the srs.db was created once by qgis_srs.sh and
>> postprocess_srs.sql, now it is maintained by hand but also
>> automatically updated (records are overwritten!?) by data from GDAL
>> during compilation, right?
>
> And on package install - to match the local GDAL and probably proj.4. IIRC only
> the existing entries get updated and none gets deleted or added.
>
>> My question/proposal: should not it all work vice versa? I.e. fill an
>> empty srs.db with the latest data from GDAL first and then to add the
>> missing projections/params? All the additional projections added by
>> QGIS should be maintained in a readable text file (not in an sqlite
>> binary).
>
> No sure, in the past nobody was actually really capable of maintaining that
> database.  People usually tend to known only the few projections they use and
> hardly can judge projections others supply.   Moreover there were issues with
> CRS coming from GDAL/OGR when the database didn't match their definition.
>
> So "we" "outsourced" that to GDAL by introducing crssync.

But in fact, at this moment, we do maintain 3906 records in tbl_srs in
resources/srs.db and occasionally we add requested missing records but
it is difficult to trace down what/why/when was changed and it is not
clear which records from resources/srs.db are necessary addition to
GDAL and what is just duplication.

If we decide to fully rely on GDAL we should do it 100%, that means we
should delete everything from resources/srs.db but that means that
QGIS becomes suddenly unusable for people who contributed missing CRS
to QGIS but not to GDAL.

I don't say that we should maintain the whole database but we should
have an option to add what is missing. My suggestion is to fill empty
srs.db by data from GDAL during compilation/installation and then add
missing CRS from a text file. The initial version of the file with
additional CRS could be created as difference of current
resources/srs.db and GDAL if it gives reasonable data (not too many
records).

Radim

>
> JÃrgen
>
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