[postgis-users] Subdividing a polygon (rectangle) into equal segments (smaller rectangles)

[BladeOfLight16]

On Wed, Aug 14, 2013 at 6:01 PM, René Fournier <m5 at renefournier.com> wrote:

> The reason is that each of the rectangles are actually subdivided into 12
> smaller, equal rectangles, numbered/lettered A-L. How would you go about
> doing this? It doesn't seem like something I can compute in the initial
> query to retrieve the containing rectangle… Any ideas?
>

Sounds to me like you have data your database isn't modeling. Any
particular reason you don't want to store the further divided rectangles?

Assuming you have a reason you don't want to,
width_bucket<http://www.postgresql.org/docs/9.2/static/functions-math.html>comes
to mind:

SELECT width_bucket(ST_X(point), ST_XMin(rect), ST_XMax(rect), 4) AS
horizontal_subrect
     , width_bucket(ST_Y(point), ST_YMin(rect), ST_YMax(rect), 3) AS
vertical_subrect
FROM (SELECT ST_GeomFromText('POLYGON ((0 0,0 100,100 100,100 0,0 0))') AS
rect) r
   , (SELECT ST_MakePoint(50,50) AS point) p;

gives

horizontal_subrect = 3, vertical_subrect = 2. You would need to be able to
coordinate that column and row number to a rectangle letter, of course.


Someone else might be able to expound on this a bit more about whether it's
a good idea, but if your data is always rectangles, maybe Box2D would be
better than geometry.

SELECT ST_MakeBox2D(ST_MakePoint(0,0), ST_MakePoint(10,10));

I'm not sure if that gives any performance gains, but I wouldn't be
surprised at all if it did.
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