This topic describes the ST_As3DGrid function. This function converts a 3D geometry into a geographic grid.
Syntax
geomgrid[] ST_As3DGrid(geometry geom3d, integer precision, bool degenerated default false);
geomgrid[] ST_As3DGrid(meshgeom geom3d, integer precision, bool degenerated default false);
geomgrid[] ST_As3DGrid(sfmesh geom3d, integer precision, bool degenerated default false);
geomgrid[] ST_As3DGrid(vomesh geom3d, integer precision, bool degenerated default false);Parameters
Parameter | Description |
geom3d | The geometry for which you want to calculate the geographic grid. |
precision | The precision level of the geographic grid. Valid values: 1 to 32. |
degenerated | Specifies whether to use a degenerated grid. |
Description
The geometry must use the CGC2000 spatial reference system. In addition, the spatial reference system identifier (SRID) of the geometry must be 4490. If the geometry does not use the CGC2000 spatial reference system, make sure that the coordinates of the geometry can be converted into CGC2000 coordinates.
An array of geographic grids that intersect with the geometry is returned. The following figure shows an example.
Examples
SELECT ST_AsText(ST_As3DGrid(
'srid=4490;LINESTRING Z (116 39 2000,116.012 39.009 3000)'::geometry, 10));
st_astext
-------------------------------------------------------
{GZ0026204626,GZ0026204662,GZ0026206404,GZ0026206440}
SELECT ST_AsText(ST_As3DGrid(st_meshgeomfromtext('srid=4490;SOLID=TRUE;MESHGEOM(PATCH(INDEXSURFACE Z (VERTEX(115.966 38.9757000000001 3000,
116 38.9757000000001 3000,116 38.9999999999999 3000,115.966 38.9999999999999 3000,116 38.9999999999999 0,
116 38.9757000000001 0,115.966 38.9757000000001 0,115.966 38.9999999999999 0),
INDEX((0,1,2),(2,3,0),(4,5,6),(6,7,4),(3,7,6),(6,0,3),(0,6,5),(5,1,0),(1,5,4),(4,2,1),(2,4,7),(7,3,2)))))'),10));
st_astext
-------------------------------------------------------
{GZ0026204626,GZ0026206404,GZ4026204626,GZ4026206404}
SELECT ST_AsText(ST_As3DGrid(st_meshfromtext(
'{"version" : 1, "srid" : 4490, "root" : 0,
"meshgeoms" : ["MESHGEOM(PATCH(POLYGON Z ((0 0 0,1 0 0,1 1 0,0 1 0,0 0 0))))"],
"primitives" : [{"meshgeom" : 0}], "nodes" : [{"primitive" : 0,"matrix" : [0.012,0,0,116,0,0.009,0,39,0,0,1000,0,0,0,0,1]}]}'),8,true));
st_astext
-----------------------------------------------
{GZ00262046,GZ00262064,GZ40262046,GZ40262064}
SELECT ST_AsText(ST_As3DGrid(ST_VOMeshFromText(
'SRID=4490;LOD=2;VOMESH(VERTEX(COORDS(116.012 39 0,116 39.009 0,115.988 39 0,116 38.991 0,116 39 1000)),
FACE(INDEX((0,1,2,3),(1,0,4),(2,1,4),(3,2,4),(0,3,4))),
CELL(INDEX((0,1,2,3,4)),DIRECTION((0,1,1,1,0))))'),15, true));
st_astext
---------------------------------------------------------------------------------------
------------------------------------------------------------
{GZ002620462666066,GZ002620466222022,GZ002620640444044,GZ002620644000000,GZ402620462666066,
GZ402620466222022,GZ402620640444044,GZ402620644000000}