[Qgis-user] [PROPOSAL] From srs.db to file-based CRS storage

[Marco Hugentobler]

Hi David

 >I would guess that the SQLite solution performs better than proj.4

QGIS uses also the proj4 library to do coordinate transformations

>On recommendation for improving performance in applications
>like MapServer that use proj.4 is to delete out the SRS definitions
>that you will never use

QGIS uses a CRS cache to lookup definitions by epsg value (avoids too 
many access to sqlite file, especially for QGIS server).

Regards,
Marco


On 30.01.2012 22:17, David Fawcett wrote:
> I am definitely not advocating for a switch to a different CRS database.
>
> I would guess that the SQLite solution performs better than proj.4 as
> well.  On recommendation for improving performance in applications
> like MapServer that use proj.4 is to delete out the SRS definitions
> that you will never use...
>
> David.
>
> On Mon, Jan 30, 2012 at 3:07 PM, Andreas Neumann<a.neumann at carto.net>  wrote:
>> Well - in my opinion, if one really wants to edit CRS it would be best
>> to document the process well in the manual and leave the CRS storage  as is.
>>
>> 1. - one doesn't need to edit the definitions very often
>> 2. - one needs to do it very carefully. CRS definitions are far more
>> complex than SQL in my opinion. You really need to know what you do or
>> your data will end up corrupted.
>> 3. - SQLite databases are very accessible. Even QGIS can be used to open
>> and edit the tables. SQLiteMan comes with every Linux distribution and
>> also as a firefox plugin.
>> 4. - with SQLite, the data is at least structure. With text-based
>> formats you need to parse the format and you open doors for mistakes and
>> unstructured data.
>> 5. - if definitions are missing, people should contribute them to the
>> project so others can use them as well.
>>
>> Just my two cents.
>>
>> Andreas
>>
>> On 01/30/2012 09:31 PM, Alexander Bruy wrote:
>>> Hi Andreas,
>>>
>>> 2012/1/30 Andreas Neumann<a.neumann at carto.net>:
>>>> srs.db is file-based already. You can easily edit and update it with any
>>>> sqlite compatible db application, such as sqliteman, openoffice, qgis,
>>>> firefox, etc.
>>> Working with sqlite requires SQL knowledge and database manager/editor,
>>> while moving and editing flat text files is much easier for ordinal users.
>>>
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-- 
Dr. Marco Hugentobler
Sourcepole -  Linux&  Open Source Solutions
Churerstrasse 22, CH-8808 Pfäffikon SZ, Switzerland
marco.hugentobler at sourcepole.ch http://www.sourcepole.ch
Technical Advisor QGIS Project Steering Committee