[postgis-users] >2D rectangular predicates?

[Chris Nicholas]

hmmm - perhaps the straight "@", "~", and "&&" will just work with 3D 
boxes..? that would be way cool...

Chris

Chris Nicholas wrote:

> Hi - I was wondering whether the underlying GiST, etc mechanisms might 
> support >2D bounding box queries efficiently... I really want to do 
> fast queries againt BIG tables like :
>
> select foo from stuff where CONTAINS( <3/4D bounding box>, the_geom),
>
> now, I realize one might do a subselect  in 2D, and then proceed with 
> measures,  but I'm intrigued by the "cube" stuff I'm seeing in 
> contrib/cube, and wondering if I might use non-cubic rectangular 
> regions instead.
>
> thanks in advance for any words of wisdom, RTFMs, etc.
>
> Chris
>
> --------------------------------------------------------------------
>
>
>  [postgis-users] 3d Points
>
> *strk at refractions.net * strk at refractions.net 
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>
> /Mon Aug 1 11:07:50 PDT 2005/
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> ------------------------------------------------------------------------
>
> On Mon, Aug 01, 2005 at 07:47:38PM +1000, Christian Heine wrote:
> ...
>
>> / Is it advisable to use EWKT or is it better to create an extra z- 
>
> />/ value column and keep the z-value separated from the lon/lat?
> /
> You don't loose anything using the extra Z-value column, you
> can always extract 2d-version or OGC-standard representation from
> a 3d object.
>
>> / Also,  
>
> />/ what is the difference between POINTM and POINT? I couldn't find 
> any  />/ information explaining the "M".
> /
> "M" stand for "Measured". It's an additional coordinate you can use
> for time or rilevated distance or whatever other parameter you
> can associate to a vertex of your geometry.
>
> In PostGIS we use the M suffix to specify that the
> tree dimensions given are X,Y,M instead of X,Y,Z.
>
> Examples:
>
>     POINT(0 0)    <---- X,Y (2D)
>     POINT(0 0 0)    <---- X,Y,Z (3DZ)
>     POINTM(0 0 0)    <---- X,Y,M (3DM)
>     POINT(0 0 0 0)    <---- X,Y,Z,M (4D)
>
> Distinction between 3DZ and 3DM is there to store
> semantic of the third parameter. Some operations
> would compute an appropriate value for the 3rd
> dimension if and only if it is a Z (and not an M).
>
> --strk;
>
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