SDO_UTIL.SIMPLIFYVW

Format

SDO_UTIL.SIMPLIFYVW(
     geometry         IN SDO_GEOMETRY, 
     vertex_threshold IN NUMBER, 
     tolerance        IN NUMBER DEFAULT 0.0000005, 
     remove_loops     IN NUMBER DEFAULT 0 
     ) RETURN SDO_GEOMETRY;

Description

Simplifies the input geometry, based on a threshold value, using the Visvalingham-Whyatt algorithm.

Parameters

geometry

Geometry to be simplified.

vertex_threshold

Threshold value to be used for the geometry simplification, expressed as a percentage value between 0 and 100. As the value is decreased, the returned geometry is likely to be closer to the input geometry; as the value is increased, fewer points are likely to be in the returned geometry.

You may want to experiment with different values to get the desired level of simplification.

tolerance

Tolerance value (see Tolerance). If you do not specify a value, the default value is 0.0000005.

remove_loops

For some line geometries, when the line is simplified, it might end up with self-crossing loops in the middle. While this is a valid geometry (for lines), in some cases it is not desirable to have these loops in the result of the simplify operation. A value of 0 (the default) does not remove such loops; a value of 1 (or any other nonzero positive number) removes any such loops and always returns simple line segments.

Usage Notes

Note:

SDO_UTIL.SIMPLIFYVW function is not supported in Oracle Autonomous Database Serverless deployments.

See the Usage Notes for the SDO_UTIL.SIMPLIFY function, which also simplifies an input geometry but uses a different algorithm (Douglas-Peucker).

Examples

The following example simplifies the same line string geometry used in the example for SDO_UTIL.SIMPLIFY.

SELECT SDO_UTIL.SIMPLIFYVW(
  SDO_GEOMETRY(
    2002,  -- line string, 2 dimensions (X,Y)
    NULL,
    NULL,
    SDO_ELEM_INFO_ARRAY(1,2,1), -- one line string, straight segments
    SDO_ORDINATE_ARRAY(
      2,2,   -- Starting point
      2,4,
      8,4,
      12,4,
      12,10,
      8,10,
      5,14)  -- Ending point
  ),
  80, -- threshold "percentage" value for geometry simplification
  0.5  -- tolerance
) FROM DUAL;

SDO_UTIL.SIMPLIFYVW(SDO_GEOMETRY(2002,--LINESTRING,2DIMENSIONS(X,Y)NULL,NULL,SDO
--------------------------------------------------------------------------------
SDO_GEOMETRY(2002, NULL, NULL, SDO_ELEM_INFO_ARRAY(1, 2, 1), SDO_ORDINATE_ARRAY(
2, 2, 12, 4, 5, 14))

Note that the resulting geometry in this case, using 80 as the vertex_threshold value, has the same points as the example for SDO_UTIL.SIMPLIFY, but without any measure dimension information (that is, the vertices are 2,2, 12,4, and 5,14). A significantly lower vertex_threshold value would probably result in a geometry with more vertices.