Returns a copy of the geometry with all points snapped to the specified grid.
geometry-expression.ST_SnapToGrid(origin,cell-size-x,cell-size-y,cell-size-z,cell-size-m)
Name | Type | Description |
---|---|---|
origin |
ST_Point |
The origin of the grid. |
cell-size-x |
DOUBLE |
The cell size for the grid in the X dimension. |
cell-size-y |
DOUBLE |
The cell size for the grid in the Y dimension. |
cell-size-z |
DOUBLE |
The cell size for the grid in the Z dimension. |
cell-size-m |
DOUBLE |
The cell size for the grid in the M dimension. |
ST_Geometry Returns the geometry with all points snapped to the grid.
The spatial reference system identifier of the result is the same as the spatial reference system of the geometry-expression.
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.
Reducing precision may cause the resulting geometry to have different properties. For example, it may cause a simple linestring to cross itself, or it may generate an invalid geometry.
Each spatial reference system defines a grid that all geometries are automatically snapped to. You can not store more precision than this predefined grid.
By default, ST_SnapToGrid uses the original format for a geometry, if it is available. Otherwise, the internal format is used. For more information about internal and original formats, see STORAGE FORMAT clause, CREATE SPATIAL REFERENCE SYSTEM statement.
SQL/MM (ISO/IEC 13249-3: 2006) Vendor extension
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 ).
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