[GRASS-dev] single vs. multiple sqlite db files [was v.db.calc]

[Benjamin Ducke]

Hamish wrote:
> Dylan:
>> I also agree on this matter. I think that one thing that is making
>> this decision particularly difficult is that we are lacking a robust
>> interchange format for complex vector data.
> 
> I guess we need to create v.pack, v.unpack modules. should be much easier
> than the r.pack, r.unpack.

Unless we take "interchange" to include other GIS. I find it frustrating
that there is no established vector data format that adequately
preserves information between different systems. SQLite + WKT/WKB
should be a good and simple way to provide that. It is easy to
turn an SQLite DB into a spatial database, following these guidelines:

http://trac.osgeo.org/fdo/wiki/FDORfc16

Of course, OGR/GDAL already has support for this "standard":

http://www.gdal.org/ogr/drv_sqlite.html

but I imagine it would be more convenient if GRASS supported it
natively?

Data exchange with other GIS apps could also be managed by pumping
(WKT/WKB) SQL statements through stdin/stdout, without the need to
go through a file, at all (of course both ends would need to
support this).

In the interim, why not create a nice wrapper module that uses the OGR
SQlite driver to store/extract attributes and geometries?

SpatiaLite is just one (albeit very nice!) implementation of that
general idea, which should be fairly easy to implement in GRASS.
The biggest problem with the current SpatiaLite API re. GRASS seems
to be that it caters for 2D coordinates only. I am not sure how hard
it would be to work around that limitation.

Ben

> 
> 
>> Dumping from GRASS vectors --> shapefiles --> 
>> GRASS can sometimes lead to data loss.
> 
> (make that often)
> 
> 
> to move forward on this I guess we need to start coding the easy way to
> switch between per-map and per-mapset sqlite modes. there seems to be
> enough support for both ways to warrant it.
> 
> 
> Hamish
> 
> 
> 
>       
> 
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> 


-- 
Benjamin Ducke
Senior Geospatial Consultant

Oxford Archaeology
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benjamin.ducke at oxfordarch.co.uk




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