PostGIS
Synopsis
geometry +`*`+ST_SnapToGrid*(`geometry `geomA, float
originX, float originY, float sizeX, float sizeY`)`;
geometry +`*`+ST_SnapToGrid*(`geometry `geomA, float
sizeX, float sizeY`)`;
geometry +`*`+ST_SnapToGrid*(`geometry `geomA, float
size`)`;
geometry +`*`+ST_SnapToGrid*(`geometry `geomA, geometry
pointOrigin, float sizeX, float sizeY, float sizeZ,
float sizeM`)`;
Description
Variant 1,2,3: Snap all points of the input geometry to the grid defined by its origin and cell size. Remove consecutive points falling on the same cell, eventually returning NULL if output points are not enough to define a geometry of the given type. Collapsed geometries in a collection are stripped from it. Useful for reducing precision.
Variant 4: Introduced 1.1.0 - Snap all points of the input geometry to the grid defined by its origin (the second argument, must be a point) and cell sizes. Specify 0 as size for any dimension you don’t want to snap to a grid.
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Availability: 1.0.0RC1
Availability: 1.1.0 - Z and M support
This
function supports 3d and will not drop the z-index.
Examples
--Snap your geometries to a precision grid of 10^-3
UPDATE mytable
SET geom = ST_SnapToGrid(geom, 0.001);
SELECT ST_AsText(ST_SnapToGrid(
ST_GeomFromText('LINESTRING(1.1115678 2.123, 4.111111 3.2374897, 4.11112 3.23748667)'),
0.001)
);
st_astext
-------------------------------------
LINESTRING(1.112 2.123,4.111 3.237)
--Snap a 4d geometry
SELECT ST_AsEWKT(ST_SnapToGrid(
ST_GeomFromEWKT('LINESTRING(-1.1115678 2.123 2.3456 1.11111,
4.111111 3.2374897 3.1234 1.1111, -1.11111112 2.123 2.3456 1.1111112)'),
ST_GeomFromEWKT('POINT(1.12 2.22 3.2 4.4444)'),
0.1, 0.1, 0.1, 0.01) );
st_asewkt
------------------------------------------------------------------------------
LINESTRING(-1.08 2.12 2.3 1.1144,4.12 3.22 3.1 1.1144,-1.08 2.12 2.3 1.1144)
--With a 4d geometry - the ST_SnapToGrid(geom,size) only touches x and y coords but keeps m and z the same
SELECT ST_AsEWKT(ST_SnapToGrid(ST_GeomFromEWKT('LINESTRING(-1.1115678 2.123 3 2.3456,
4.111111 3.2374897 3.1234 1.1111)'),
0.01) );
st_asewkt
---------------------------------------------------------
LINESTRING(-1.11 2.12 3 2.3456,4.11 3.24 3.1234 1.1111)