[postgis-users] PointM, PolyLineM, PolygonM, ...

[strk at refractions.net]

On Thu, Sep 23, 2004 at 12:12:28PM +0200, Pierrick Brihaye wrote:
> Hi,
> 
> strk at refractions.net a écrit :
> 
>  > Now that postgis supports up to 4 dimensions geometry, what do you
> >think should be done ? My vision is this:
> >
> >Type  <-> geometry2d
> >TypeM <-> geometry3d
> >TypeZ <-> geometry4d
> >
> >What do you think ?
> 
> How long shall we pay for ESRI's weird data model ? :-)
> 
> IMHO, the 3rd dimension has well-known semantics : Z.
> 
> Therefore, any other dimension should be considered as a 4th one.
> 
> Any other thoughts ?

I'm with you, but quetions are:

1) how should we import TypeM shapefiles ?
	a) as x,y,Z,m // wasting Z space in postgis 
	b) as x,y,z   // interpreting M as Z

2) how should we import TypeZ shapefiles ?
	a) as x,y,z,m // respecting shapefile meanings 
	b) as x,y,z,m // swapping M<->Z meaning
	c) as x,y,z   // discarding M
	d) as x,y,z   // using M, discarding Z

3) how should we export geometry3d ?
	a) as TypeM // using M for Z values
	b) as TypeZ // wasting M space in shapefile

3) how should we export geometry4d ?
	a) as TypeZ // respecting shapefile meanings (4th dim -> M)
	b) as TypeZ // swapping M<->Z meaning

Does anyone see the light ?
I suppost some command line switches would do but finding an easy
interface is not straightforward ...

--strk;

> 
> Regards,
> 
> -- 
> Pierrick Brihaye, informaticien
> Service régional de l'Inventaire
> DRAC Bretagne
> mailto:pierrick.brihaye at culture.gouv.fr
> +33 (0)2 99 29 67 78
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