pgr_separateCrossing
¶
pgr_separateCrossing
- From crossing geometries generates geometries that
do not cross.
Disponibilidad
Versión 3.8.0
Función promovida a oficial.
Proposed function.
Descripción¶
This is an auxiliary function for separating crossing edges.
Firma¶
(seq,id,sub_id,geom)
- Ejemplo:
Get the segments of the crossing geometries
SELECT id, sub_id, ST_AsText(geom)
FROM pgr_separateCrossing('SELECT id, geom FROM edges')
ORDER BY id, sub_id;
id | sub_id | st_astext
----+--------+---------------------------
13 | 1 | LINESTRING(3 3,3.5 3)
13 | 2 | LINESTRING(3.5 3,4 3)
18 | 1 | LINESTRING(3.5 2.3,3.5 3)
18 | 2 | LINESTRING(3.5 3,3.5 4)
(4 rows)
Parámetros¶
Parámetro |
Tipo |
Descripción |
---|---|---|
|
SQL de aristas como se describe a continuación |
Parámetros opcionales¶
Parámetro |
Tipo |
x Defecto |
Descripción |
---|---|---|---|
|
|
0.01 |
Used in ST_Snap before ST_Split |
|
|
|
|
Consultas Internas¶
SQL aristas¶
Columna |
Tipo |
Descripción |
---|---|---|
|
ANY-INTEGER |
(Opcional) identificador de la arista. |
|
|
Geometría de la arista. |
Ejemplos¶
Get the code for further refinement.¶
When there are special details that need to be taken care of because of the
final application or the quality of the data, the code can be obtained On a
PostgreSQL NOTICE
using the dryrun
flag.
SELECT *
FROM pgr_separateCrossing('SELECT id, geom FROM edges', dryrun => true);
NOTICE:
WITH
edges_table AS (
SELECT id, geom FROM edges
),
get_crossings AS (
SELECT e1.id id1, e2.id id2, e1.geom AS g1, e2.geom AS g2, ST_Intersection(e1.geom, e2.geom) AS point
FROM edges_table e1, edges_table e2
WHERE e1.id < e2.id AND ST_Crosses(e1.geom, e2.geom)
),
crossings AS (
SELECT id1, g1, point FROM get_crossings
UNION
SELECT id2, g2, point FROM get_crossings
),
blades AS (
SELECT id1, g1, ST_UnaryUnion(ST_Collect(point)) AS blade
FROM crossings
GROUP BY id1, g1
),
collection AS (
SELECT id1, (st_dump(st_split(st_snap(g1, blade, 0.01), blade))).*
FROM blades
)
SELECT row_number() over()::INTEGER AS seq, id1::BIGINT, path[1], geom
FROM collection;
;
seq | id | sub_id | geom
-----+----+--------+------
(0 rows)
Encontrando una intersección¶
In this example the original edge table will be used to store the additional geometries.
An example use without results
Routing from
SELECT *
FROM pgr_dijkstra('SELECT id, source, target, cost, reverse_cost FROM edges', 1, 18);
seq | path_seq | start_vid | end_vid | node | edge | cost | agg_cost
-----+----------+-----------+---------+------+------+------+----------
(0 rows)
Analyze the network for intersections.
SELECT
e1.id id1, e2.id id2,
ST_AsText(ST_Intersection(e1.geom, e2.geom)) AS point
FROM edges e1, edges e2
WHERE e1.id < e2.id AND ST_Crosses(e1.geom, e2.geom);
id1 | id2 | point
-----+-----+--------------
13 | 18 | POINT(3.5 3)
(1 row)
The analysis tell us that the network has an intersection.
Prepare tables
Additional columns to control the origin of the segments.
ALTER TABLE edges ADD old_id BIGINT;
ALTER TABLE
Adding new segments.
Calling pgr_separateCrossing and adding the new segments to the edges table.
INSERT INTO edges (old_id, geom)
SELECT id, geom
FROM pgr_separateCrossing('SELECT id, geom FROM edges');
INSERT 0 4
Update other values
In this example only cost
and reverse_cost
are updated, where they are
based on the length of the geometry and the directionality is kept using the
sign
function.
WITH
costs AS (
SELECT e2.id, sign(e1.cost) * ST_Length(e2.geom) AS cost,
sign(e1.reverse_cost) * ST_Length(e2.geom) AS reverse_cost
FROM edges e1 JOIN edges e2 ON (e1.id = e2.old_id)
)
UPDATE edges e
SET (cost, reverse_cost) = (c.cost, c.reverse_cost)
FROM costs AS c WHERE e.id = c.id;
UPDATE 4
Actualizar la topología
Insert the new vertices if any.
WITH
new_vertex AS (
SELECT ev.*
FROM pgr_extractVertices('SELECT id, geom FROM edges WHERE old_id IS NOT NULL') ev
LEFT JOIN vertices v using(geom)
WHERE v IS NULL)
INSERT INTO vertices (in_edges, out_edges,x,y,geom)
SELECT in_edges, out_edges,x,y,geom FROM new_vertex;
INSERT 0 1
Actualizar la salida y el destino en la tabla de aristas.
/* -- set the source information */
UPDATE edges AS e
SET source = v.id, x1 = x, y1 = y
FROM vertices AS v
WHERE source IS NULL AND ST_StartPoint(e.geom) = v.geom;
UPDATE 4
/* -- set the target information */
UPDATE edges AS e
SET target = v.id, x2 = x, y2 = y
FROM vertices AS v
WHERE target IS NULL AND ST_EndPoint(e.geom) = v.geom;
UPDATE 4
The example has results
Routing from
SELECT *
FROM pgr_dijkstra('SELECT id, source, target, cost, reverse_cost FROM edges', 1, 18);
seq | path_seq | start_vid | end_vid | node | edge | cost | agg_cost
-----+----------+-----------+---------+------+------+------+----------
1 | 1 | 1 | 18 | 1 | 6 | 1 | 0
2 | 2 | 1 | 18 | 3 | 7 | 1 | 1
3 | 3 | 1 | 18 | 7 | 10 | 1 | 2
4 | 4 | 1 | 18 | 8 | 12 | 1 | 3
5 | 5 | 1 | 18 | 12 | 19 | 0.5 | 4
6 | 6 | 1 | 18 | 18 | -1 | 0 | 4.5
(6 rows)
Ver también¶
Topología - Familia de Funciones para una visión general de una topología para algoritmos de enrutamiento.
Índices y tablas