[GRASS-dev] better mysql support

[Paul Kelly]

On Sun, 15 Apr 2007, Emanuele Conti wrote:

> Hi everybody,
> I'm a university student and I'm doing a thesis on the integration of grass
> with mysql. I found that grass has a good support for postgis and I'd like
> to duplicate all the main features available for this db for mysql, which
> has geometry extensions (opengis compliant) and performs significantly
> better than postgres. I downloaded grass 6.3 cvs source code yet and I

As I understand it the OpenGIS vector format is a lot less featureful than 
the GRASS format (i.e. it doesn't store the topological relationships 
between vector features, which is important for a lot of vector analyses) 
and thus it is debateable whether it is useful to store GRASS data in that 
format. It would mean topology would have to be re-built from the external 
data any time an analysis is to be done in GRASS. My understanding is the 
OpenGIS format is more of a quick-access format useful for displaying 
data, but if it is to be edited, topological format is better for ensuring 
the integrity of the data (no overlapping boundaries and that kind of 
thing).

As far as I can remember GRASS used to directly support storage of vector 
geometry in PostGIS in 5.7/6.0 pre-releases, but that was removed before 
the release of 6.0.0 final because there were problems with it. The 
PostGIS support was integrated by a group of final year project students I 
think - there may also have been a paper written about it. It would 
probably be a good idea to investigate this (e.g. download an old version 
of GRASS and try it out etc.) and investigate what the problems were and 
why it was dropped, and see if you can do better with your MySQL spatial 
support.

Off the top of my head though, I think the shortcomings of the OpenGIS 
vector format for spatial analysis were a major factor. But you would need 
to read old mailing list posts from Radim Blazek for more insight.

Paul

> started to have a look to the code, but I've some questions:
> - from the grass 6 features page I understood that with postGis it's no more
> necessary to pass through gdal ogr translation: is this true? Is there a
> direct db manipulation?
> - what part of the code implements the direct "Export/Import to
> *PostGIS"*(functions as
> v.to.db and so on) and which directories and files should I look at?
> - what documentation could help me and where could I find it (I googled for
> technical docs oriented to grass/db integration, but I did't found much
> material);
> - is this a project that could become part of grass in any way? How could I
> receive support and/or feedback when necessary?
>
> I hope to read of you soon. Thanks...
>
> -- 
> Emanuele Conti
> Senior Student at University ROMA TRE
> Department of Informatics and Automation
> ROME, Italy (matr. 251318)
> Mob:       +39 328 2681070
> Home:     +39 06 39741124
> e-mail:     emanuele.conti at yahoo.com
> y!:            emanuele_c
> msn:        emanuele_c at yahoo.com
>