[postgis-users] Topology & Attributes

[Nicolas Ribot]

Hi,

When you build the topology, for instance with topology.toTopoGeom(), you
get back a TopoGeometry object for each polygon added to the topology.
This TopoGeometry is used to keep a link between your polygon object and
all the topological elements composing it.
The "relation" table inside the topo schema holding the topology contains
the identifier of the topoGeometry object and the identifiers of topo
elements composing the polygon.

To get the right and left original polygons from the topology, you make a
join between edge, relation and pg table:
(topo_grass is the topo schema, parcelle is the polygon table with a topo
column containing the TopoGeometry object corresponding to the polygon):

select e.edge_id, e.left_face, e.right_face,
  p1.id as left_id, p2.id as right_id
from topo_grass.edge e
  join topo_grass.relation r1 on r1.element_id = e.left_face
  join pe.parcelle p1 on (1, (p1.topo).id) = (r1.layer_id, r1.topogeo_id)
  join topo_grass.relation r2 on r2.element_id = e.right_face
  join pe.parcelle p2 on (1, (p2.topo).id) = (r2.layer_id, r2.topogeo_id);

Nicolas



On 8 February 2015 at 10:29, Ofer Zilberstein <zilberstein.ofer at gmail.com>
wrote:

>
> Hi,
>
> When you build topology from set of connected polygons, the original
> polygon attributes are not part of the topology model. The model creates
> MBR face for each original polygon.
>
> The edges hold the left & right faces.
>
> How or what is the right way to add to the edges the right and left
> original polygons ?
>
> --
>
> *Ofer Zilberstein*
>
>     Mobile: 972-544886873
>
>     Skype: ofer.zilberstein
>
>     Mail: zilberstein.ofer at gmail.com
>
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