[postgis-users] value of spatial index on 300, 000, 000 point geometries

[Paul Ramsey]

Brent,

The key when binning is to ensure that your rows are not larger than
the page size (8KB). If we say your 3D points take 25 bytes (3 doubles
plus type overhead), then the actual max number of points in a patch
would be 327. From that subtract size for other attributes you might
be carrying.

P.

On Tue, May 5, 2009 at 9:22 PM,  <pcreso at pcreso.com> wrote:
>
>
> Thanks for the suggestions, much appreciated as always!!
>
>
> That sounds interesting. I'm currently storing XY points in a 2d geometry, with a separate depth column. I could convert these to 3D points to retain the z value of each point when stored as a multipoint.
>
> I have not used 3D geometries before, so a quick followup to ask about any caveats or advice you may have to offer on this approach, basically generating the 3D points, then using Kevin's approach to binning these say every 0.5 degrees.
>
> Does ST_SnapToGrid work on 3D geometries? I only want them snapped by XY, not Z.
>
> My Z units are m, my X&Y are degrees. Any issues there?
>
> I assume any transform() operations will simply pass through the Z value unchanged?
>
>
> Thanks,
>
>   Brent Wood
>
>
>
> --- On Wed, 5/6/09, Kevin Neufeld <kneufeld at refractions.net> wrote:
>
>> From: Kevin Neufeld <kneufeld at refractions.net>
>> Subject: Re: [postgis-users] value of spatial index on 300, 000, 000 point geometries
>> To: "PostGIS Users Discussion" <postgis-users at postgis.refractions.net>
>> Date: Wednesday, May 6, 2009, 2:06 PM
>> Yes, I had to store a table of 3D DEM
>> point data (~170million) in a
>> database once.   As Paul mentioned, there
>> can be great benefits of
>> grouping your points into multipoint objects.
>> Consider that if you
>> convert your points into groups of 200, the index could be
>> up to 200
>> times smaller.
>
>
> _______________________________________________
> postgis-users mailing list
> postgis-users at postgis.refractions.net
> http://postgis.refractions.net/mailman/listinfo/postgis-users
>