[postgis-users] help setting up postgis

[Nicolas Ribot]

On 17 August 2010 17:11, Jan Saalbach <fire at dubmosphere.de> wrote:
> Nicolas, thank you for your help. I have imported a set of points using a
> python to psql script which filled a GeometryColumn using the ST_MakePoint()
> function.
>
> Now I would like to visualize the points using uDig. Since the set imported
> is comprised of around 10 million points, drawing each point is not
> possible. What I would like to do is create and just draw a bounding box of
> the set of points. This way I could compare it to another set of points in
> respect of the position to each other.
>
> The thing I do not know yet is how to do it using postgis , i.e. which
> commands I need. Any tips on how I could go about visualizing two datasets
> of scattered points?
>
> Regards,
> Jan
>

Hi

There were some threads about displaying such points set.

Concerning the first question, you can use the table function
st_extent(), that returns the bounding box of a set of rows.
You could also use st_convexHull, to create a geometry representing
the convex hull of your point set, which will give you a more precise
picture of the pointset span. But it will take more time to compute.

Nicolas