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Using JTS's Comparison Functions - HausdorffSimilarityMeasure & AreaSimilarityMeasure with SDO_GEOMETRY
Saturday September 10 2011 at 21:25
There is often a need to compare SDO_GEOMETRYs to see if a geometry has changed or not. The SDO_GEOM.RELATE function is useful in this regards where two geometries are EQUAL but it is not fine-grained enough to help understand how different two things are. The Java Topology Suite (JTS) has two very useful match algorithms in its com.vividsolutions.jts.algorithm.match package.
I have extended my JTS package and installer to expose the two methods JTS makes available:
- HausdorffSimilarityMeasure (Supports lines and polygons)
- AreaSimilarityMeasure (Supports only areas)
Martin Davis has a good article on the HausdorffSimilarityMeasure on his website.
Here are some examples.
1. Call to both functions using two identical area sdo_geometry
WITH myGeoms AS ( SELECT MDSYS.SDO_GEOMETRY(2003, NULL, NULL, MDSYS.SDO_ELEM_INFO_ARRAY(1,1003,3), MDSYS.SDO_ORDINATE_ARRAY(100.0, 100.0, 500.0, 500.0)) AS area1, geom.rectangle2polygon(MDSYS.SDO_GEOMETRY(2003, NULL, NULL, MDSYS.SDO_ELEM_INFO_ARRAY(1,1003,3), MDSYS.SDO_ORDINATE_ARRAY(100.0, 100.0, 500.0, 500.0))) AS area2 FROM dual ) SELECT JTS.ST_HausdorffSimilarityMeasure(area1,area2,3) AS HSM, JTS.ST_AreaSimilarityMeasure(area1,area2,3) AS ASM FROM myGeoms; . HSM ASM --- --- 1 1
2. Call to both functions using two slightly different area sdo_geometrys
WITH myGeoms AS ( SELECT MDSYS.SDO_GEOMETRY(2003, NULL, NULL, MDSYS.SDO_ELEM_INFO_ARRAY(1,1003,3), MDSYS.SDO_ORDINATE_ARRAY(100.0, 100.0, 500.0, 500.0)) AS area1, geom.rectangle2polygon(MDSYS.SDO_GEOMETRY(2003, NULL, NULL, MDSYS.SDO_ELEM_INFO_ARRAY(1,1003,3), MDSYS.SDO_ORDINATE_ARRAY(100.0, 100.0, 500.01, 500.01))) AS area2 FROM dual ) SELECT JTS.ST_HausdorffSimilarityMeasure(area1,area2,3) AS HSM, JTS.ST_AreaSimilarityMeasure(area1,area2,3) AS ASM FROM myGeoms; . HSM ASM ----------------- ----------------- 0.999975000624984 0.999950001874937
3. Call to HausdorffSimilarityMeasure function only using two slightly different line sdo_geometrys
WITH myGeoms AS ( SELECT MDSYS.SDO_GEOMETRY(2002, NULL, NULL, MDSYS.SDO_ELEM_INFO_ARRAY(1,2,1), MDSYS.SDO_ORDINATE_ARRAY(0,0, 10,10, 20,0, 30,30)) AS line1, MDSYS.SDO_GEOMETRY(2002, NULL, NULL, MDSYS.SDO_ELEM_INFO_ARRAY(1,2,1), MDSYS.SDO_ORDINATE_ARRAY(0,0, 10.01,10, 20,0.1, 30,30.07)) AS line2 FROM dual ) SELECT JTS.ST_HausdorffSimilarityMeasure(line1,line2,3) AS HSM FROM myGeoms; . HSM --------------- 0.9976457256498
See my JTS package header description for the call signatures for these functions.
        
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