geometry-expression.ST_SnapToGrid(origin,cell-size-x,cell-size-y,cell-size-z,cell-size-m)

The ST_SnapToGrid method can be used to reduce the precision of data by snapping all points in a geometry to a grid defined by an origin and cell size.

You can specify a different cell size for each dimension. If you do not wish to snap the points of one dimension, you can use a cell size of zero.

• How snap-to-grid and tolerance impact spatial calculations

The following example returns the result LineString(1.010101 20.20202, 1.015625 20.203125, 1.01 20.2).

SELECT NEW ST_LineString( 
   NEW ST_Point( 1.010101, 20.202020 ),
   TREAT( NEW ST_Point( 1.010101, 20.202020 ).ST_SnapToGrid( NEW ST_Point( 0.0, 0.0 ), POWER( 2, -6 ), POWER( 2, -7 ), 0.0, 0.0 ) AS ST_Point ),
   TREAT( NEW ST_Point( 1.010101, 20.202020 ).ST_SnapToGrid( NEW ST_Point( 1.01, 20.2 ), POWER( 2, -6 ), POWER( 2, -7 ), 0.0, 0.0 ) AS ST_Point ) )

The first point of the linestring is the point ST_Point( 1.010101, 20.202020 ), snapped to the grid defined for SRID 0.

The second point of the linestring is the same point snapped to a grid defined with its origin at point ( 0.0 0.0 ), where cell size x is POWER( 2, -6 ) and cell size y is POWER( 2, -7 ).

The third point of the linestring is the same point snapped to a grid defined with its origin at point ( 1.01, 20.2 ), where cell size x is POWER( 2, -6 ) and cell size y is POWER( 2, -7 ).