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    Making Sdo Geometry Metadata
    SC4O Test log
    The Frontage Problem: Creating references from land parcel street frontage boundary to point in street
    Scheduling the Export of Spatial Data in Oracle to a Shapefile each night
    Oracle CENTROID package update
    Book: "Applying And Extending Oracle Spatial"
    Create Polygons and Linestrings From Bearings And Distances (COGO)
    Simple Implementation Of Travelling Salesman Problem
    ST_Densify for Object PLSQL
    PLSQL ST_AsEWKT and ST_FromWKT Functions For Oracle (any version)
    Useful Package of Wrapper Functions for Sdo_Util.AffineTransforms
    GeoRaptor 4.x Update 2 (Project has Stalled)
    Tip: Drop that Spatial Index!
    Convert Single Geometry to Multi-part Geometry in Oracle Spatial
    Optimized Rectangle to 5 Point Polygon
    Centroid Package now supports Y ordinate seeding
    Convert GeoJSON document to Sdo_Geometry objects
    Function That Returns a Compass Point From a Whole Circle Bearing
    Playing around with Centroids by using different seed values
    Simple Oracle C Sprintf or Java String.format
    Some Oriented Point Functions
    Extracting Inner Rings Changed Ordinate Ordering: A Trap For Players Who Don't Read Documentation!
    PLS-00306: wrong number or types of arguments in call to 'SDO_GEOMETRY'
    Converting Google Earth Formatted Longitude/Latitude points to decimal degrees
    Oracle Business Intelligence Warehousing and Analytics - Spatial Summit
    How far inside, is inside? Measuring actual distance.
    Noding and building a polygon from single, overlapping linestrings
    Analyzing Spatial Query Performance Improvements in Oracle Spatial and Graph 12c Through Cross-Vendor Comparison
    ST_VertexN / ST_PointN - Extracting a specific point from any geometry
    Convert Single Point stored in SDO_ORDINATES to SDO_POINT_TYPE
    Aggregate APPEND Islands and XOR polygons
    Circular Arcs in Geodetic Polygons
    Some SDO_GEOMETRY/DIMINFO handling functions
    Changing all DIMINFO sdo_tolerance values for all metadata records in one go.
    Building Polygons from Incomplete Linestrings using ST_PolygonBuilder
    Computing Cardinal Directions to nearby geometries
    Intersecting two aggregated polygon layers with SC4O
    Spatial and Oracle 12c
    Update Triggers and SDO_GEOMETRY Equality
    Duplicate Geometry data and Data Models
    CENTROID package update
    How to calculate cumulative length of a linestring
    Compute Location from known Lat/Long point using delta easting and northing in miles
    Sorting SDO_GEOMETRY data using the ORDER BY clause of a SELECT statement
    Creating linestrings from points
    Rounding Coordinates or Ordinates in SDO_GEOMETRY
    Effects of Sdo_Geometry Ordinate Precision on Performance
    Effects of Sdo_Geometry Ordinate Precision on Storage
    The Spatial filtering of geometries: The effect of tolerances on relationships
    Application of Delaunay Triangulation and Inverse Distance Weighting (IDW) in Oracle for Soils Interpolation
    Selecting all SDO_GTYPE values for all tables/sdo_geometry columns in a schema
    CENTROID package - Tips for Use
    Announcing the Spatial Companion For Oracle (SC4O)
    Filtering Rings (Oracle Spatial)
    Splitting a polygon using one or more linestrings
    isValid, isSimple, Dimension and CoordDim methods for SDO_Geometry
    Line Merging or Collecting lines together: ST_LineMerger
    ST_DeleteVertex for Oracle SDO_Geometry based on Jaspa/JTS
    3D/4D and SRID aware Conversion functions for SDO_Geometry: WKT and EWKT
    Topological vs Non-Topological Simplification/Generalization of Aggregated Area Geometies in Oracle
    Filtering very short linestrings via bitmap function index
    CENTROID For Oracle
    Gridding a sdo_geometry line/polygon object (Oracle)
    Finding centre and radius of a circular geometry
    Constraining geometry type for sdo_geometry column in a table.
    CASE Statements and SDO_GEOMETRY
    The Power of Constraints and Indexes for Spatial Constraints: stopping duplicate points
    Replacement for SDO_GEOM.RELATE - ST_Relate based on JTS
    Changing Oracle Spatial Index Parameters on existing index
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    Writing xSV (eg csv) files from within the Oracle database using Java and PL/SQL
    A simple spike finder for Spatial/Locator
    JTS Java class compilation for 11g and above
    Random Spatial Search Procedure
    Geometry Snapping using JTS in Oracle
    Exposing JTS's MinimumBoundingCircle functionality
    Exposing JTS's Densifier functionality
    Using JTS's Comparison Functions - HausdorffSimilarityMeasure & AreaSimilarityMeasure with SDO_GEOMETRY
    Free JTS-based Area/Length Functions
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    Standalone CENTROID package now available for download
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    Free Union, Intersection, Xor and Difference Functions for Oracle Locator - Part 2
    Free Union, Intersection, Xor and Difference Functions for Oracle Locator - Part 1
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    Finding Intersection Points between Line and Polygon
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    layer_gtype keyword issue when indexing linear data on 11g
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    Oracle Spatial DISJOINT search/filtering
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    Performance of PL/SQL Functions using SQL vs Pure Code
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    Detecting sdo_geometries with compound (3-point Arcs) segments
    GEOMETRY_COLUMNS for Oracle Spatial
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    Calling the Oracle Spatial shapefile loader from within the Oracle database itself
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    Implementing SDO_RemovePoint/ST_RemovePoint for Oracle
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    Funky Fix Ordinates By Formula
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    Oracle Spatial Centroid Shootout
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    Spatial Pipelining
    Using Oracle's SDO_NN Operator - Some examples
    Converting distances and units of measure in Oracle Locator
    Split Sdo_Geometry Linestring at a known point
    Forcing an Sdo_Geometry object to contain only points, lines or areas
    Unpacking USER_SDO_GEOM_METADATA's DIMINFO structure using SQL
    Generating multi-points from single point records in Oracle Spatial
    Object Tables of Sdo_Geometry
    Oracle Locator vs Oracle Spatial: A Reflection on Oracle Licensing of the SDO_GEOM Package
    FAST REFRESHing of Oracle Materialized Views containing Sdo_Geometry columns
    Australian MGA/AMG Zone Calculation from geographic (longitude/latitude) data
    Loading Shapefiles (SHP) into Oracle Spatial
    Oracle Spatial Mapping and Map Rendering Performance Tips
    The significance of sdo_lb/sdo_ub in USER_SDO_GEOM_METDATA: Do I need it?
    Oracle Spatial Forum - Melbourne April 2007
    Layer_GTypes for spatial indexes
    Oracle's SQL/MM Compliant Types
    Tips and Tricks



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All Blog Articles, Data Models and Free Source Code by Simon Greener, The SpatialDB Advisor is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.

Rounding Coordinates or Ordinates in SDO_GEOMETRY

Wednesday April 18 2012 at 02:23

Keywordsround ordinates coordinates tolerance sdo_geometry

This article presents a function that can be used to round the individual ordinates of the coordinates of an sdo_geometry.

Often Oracle Locator/Spatial users want to know how to round the individual ordinates of the coordinates of an sdo_geometry. This article shows how this can be done.


Oracle imposes no precision limit on the NUMBER that records an ordinate of a coordinate except that imposed by the NUMBER datatype itself.

Also, while one associates metadata with an SDO_GEOMETRY column in a table that describes a tolerance for each ordinate (see the SDO_TOLERANCE field in an SDO_DIM_ELEMENT of an SDO_DIM_ARRAY stored in xxxx_sdo_geom_metadata), it does not enforce it as INSERTs or UPDATEs are applied against the sdo_geometry column. The SDO_TOLERANCE value just mentioned, as also the tolerance or diminfo parameters of many of Oracle’s sdo_geometry functions (eg SDO_GEOM.SDO_AREA(geometry,tolerance) are only used to ensure computations are done to a specified precision. At no stage are ordinate values rounded to a specific precision.

One must also note that sdo_tolerance is not a statement of the precision of a specific ordinate: it is a statement of how close two coordinates can be to be considered to be the same!

Finally, when loading data from an external source such as a shapefile, there is often a mismatch between the way the ordinates are described depending on whether the external data source stores its values in double precision, float, integer etc.

What is a suitable precision of an Ordinate?

This depends on the “sensor” that recorded the original value:

  • Manually surveyed (with theodolite + surveyor) may be both accurate and precise recording observations down to millimeters;
  • High precision differential GPS may record ordinate values down to 1cm;
  • Cheap hand-held GPS may record a specific coordinate to a few meters precision);
  • Data scanned from an old paper/mylar map may be only accurate to +/-10-20meters!
  • Satellite data is variable in precision.

Case 1

But let’s assume we have some road centreline data that is claimed to be accurate to 0.1 of a meter or 1 digit of decimal precision. And our data was loaded from an external source and has lots of imprecise decimal digits of precision.

  2.                     SDO_ELEM_INFO_ARRAY(1,2,1),
  3.                     SDO_ORDINATE_ARRAY(-816008.499528741,-1071166.1245046,-815846.43719259,-1071166.1245046)) AS oGeom
  4.   FROM dual;
  5. -- Results
  6. --
  7. OGEOM
  8. ------------------------------------------------------------------------------------------------------------------------------------------------------------------
  9. MDSYS.SDO_GEOMETRY(2002,NULL,NULL,MDSYS.SDO_ELEM_INFO_ARRAY(1,2,1),MDSYS.SDO_ORDINATE_ARRAY(-816008.499528741,-1071166.1245046,-815846.43719259,-1071166.1245046))

Note that, given its stated observational accuracy, it has way too many digits of supposed precision when one (1 decimeter) would be sufficient.

Case 2

I mentioned above that some Oracle functions can take a tolerance value while some do not. Let’s assume we have a long/lat value (via a click on a map) and we want the Google Mercator Map coordinates for that point.

For this we can use the SDO_CS.TRANSFORM function:

  1. SELECT sdo_cs.transform(sdo_geometry(2002,8311,NULL,
  2.                                      sdo_elem_info_array(1,2,1),
  3.                                      sdo_ordinate_array(147.123,-32.456,147.672,-33.739)),3785) AS geom
  4.   FROM dual;
  5. -- Results
  6. --
  7. GEOM
  8. -------------------------------------------------------------------------------------------------------------------
  10.                    MDSYS.SDO_ELEM_INFO_ARRAY(1,2,1),
  11.                    MDSYS.SDO_ORDINATE_ARRAY(16377657.4439788,-3800381.82007675,16438771.8444243,-3970070.49100647))

Being that the input data was only specified to 0.001 of a degree, an output – in meters – specified to 8 decimal places seems somewhat excessive.

Applying a Precision to the Ordinates of a Coordinate

To apply a specific precision to the numbers in an SDO_ORDINATE array requires a relatively simply PL/SQL function. I created just such a function a long time ago which is available in my GEOM PL/SQL package available for free on this website. But here is a standalone version of it:

  2. FUNCTION RoundOrdinates(P_Geometry        IN Mdsys.Sdo_Geometry,
  3.                         P_X_Round_Factor  IN NUMBER,
  4.                         p_y_round_factor  IN NUMBER DEFAULT NULL,
  5.                         P_Z_Round_Factor  IN NUMBER DEFAULT NULL,
  6.                         p_m_round_factor  IN NUMBER DEFAULT NULL)
  8.   IS
  9.    C_I_Null_Geometry  Constant INTEGER       := -20120;
  10.    C_S_Null_Geometry  Constant Varchar2(100) := 'Input geometry must not be null';
  11.    C_I_Null_Tolerance Constant INTEGER       := -20119;
  12.    C_S_Null_Tolerance Constant Varchar2(100) := 'Input tolerance/dimarray must not be null';
  13.    v_ismeasured       BOOLEAN;
  14.    v_dim              pls_integer;
  15.    v_gtype            pls_integer;
  16.    v_measure_ord      pls_integer;
  17.    v_ord              pls_integer;
  18.    v_geometry         mdsys.sdo_geometry := p_geometry;
  19.    V_Ordinates        mdsys.Sdo_Ordinate_Array;
  20.    V_X_Round_Factor   NUMBER := P_X_Round_Factor;
  21.    V_Y_Round_Factor   NUMBER := Nvl(P_Y_Round_Factor,P_X_Round_Factor);
  22.    V_Z_Round_Factor   NUMBER := Nvl(P_z_Round_Factor,P_X_Round_Factor);
  23.    V_W_Round_Factor   NUMBER := NVL(p_m_round_factor,p_x_round_factor);
  24. BEGIN
  25.   IF ( p_x_round_factor IS NULL ) THEN
  26.     raise_application_error(c_i_null_tolerance,c_s_null_tolerance,TRUE);
  27.    END IF;
  28.   IF ( p_geometry IS NULL ) THEN
  29.      raise_application_error(c_i_null_geometry,c_s_null_geometry,TRUE);
  30.   END IF;
  31.   V_Ismeasured := CASE WHEN MOD(Trunc(p_geometry.Sdo_Gtype/100),10) = 0 THEN FALSE ELSE TRUE END;
  32.   v_gtype := MOD(p_geometry.sdo_gtype,10);
  33.   v_dim   := p_geometry.get_dims(); -- IF 9i then .... TRUNC(p_geometry.sdo_gtype/1000,0);
  34.   -- If point update differently to other shapes...
  35.   --
  36.   IF ( V_Geometry.Sdo_Point IS NOT NULL ) THEN
  37.     v_geometry.sdo_point.X := round(v_geometry.sdo_point.x,v_x_round_factor);
  38.     V_Geometry.Sdo_Point.Y := Round(V_Geometry.Sdo_Point.Y,V_Y_Round_Factor);
  39.     IF ( v_dim > 2 ) THEN
  40.       v_geometry.sdo_point.z := round(v_geometry.sdo_point.z,v_z_round_factor);
  41.     END IF;
  42.   END IF;
  43.   IF ( p_geometry.sdo_ordinates IS NOT NULL ) THEN
  44.     v_measure_ord := MOD(trunc(p_geometry.sdo_gtype/100),10);
  45.     v_ordinates := NEW mdsys.sdo_ordinate_array(1);
  46.     v_ordinates.DELETE;
  47.     v_ordinates.EXTEND(p_geometry.sdo_ordinates.COUNT);
  48.     -- Process all coordinates
  49.     <<while_vertex_to_process>>
  50.     FOR v_i IN 1..(v_ordinates.COUNT/v_dim) LOOP
  51.        v_ord := (v_i-1)*v_dim + 1;
  52.        v_ordinates(v_ord) := round(p_geometry.sdo_ordinates(v_ord),v_x_round_factor);
  53.        v_ord := v_ord + 1;
  54.        v_ordinates(v_ord) := round(p_geometry.sdo_ordinates(v_ord),v_y_round_factor);
  55.        IF ( v_dim >= 3 ) THEN
  56.           v_ord := v_ord + 1;
  57.           V_Ordinates(v_ord) := CASE WHEN V_Ismeasured
  58.                                      THEN round(p_geometry.sdo_ordinates(v_ord),v_w_round_factor)
  59.                                      ELSE round(p_geometry.sdo_ordinates(v_ord),v_z_round_factor)
  60.                                   END;
  61.           IF ( v_dim > 3 ) THEN
  62.              v_ord := v_ord + 1;
  63.              v_ordinates(v_ord) := round(p_geometry.sdo_ordinates(v_ord),v_w_round_factor);
  64.           END IF;
  65.        END IF;
  66.     END LOOP while_vertex_to_process;
  67.   END IF;
  68.   RETURN mdsys.sdo_geometry(v_geometry.sdo_gtype,
  69.                             v_geometry.sdo_srid,
  70.                             v_geometry.sdo_point,
  71.                             v_geometry.sdo_elem_info,
  72.                             V_Ordinates);
  73. END RoundOrdinates;

This function can be used in any internal Oracle processing. Let’s apply it first to our imaginary centreline:

  1. SELECT RoundOrdinates(
  2.             SDO_GEOMETRY(2002,NULL,NULL,
  3.                          SDO_ELEM_INFO_ARRAY(1,2,1),
  4.                          SDO_ORDINATE_ARRAY(-816008.499528741,-1071166.1245046,-815846.43719259,-1071166.1245046)),
  5.             1) AS rGeom
  6.   FROM dual;
  7. -- Results
  8. --
  9. RGEOM
  10. ---------------------------------------------------------------------------------------------------------------------------------------
  11. MDSYS.SDO_GEOMETRY(2002,NULL,NULL,MDSYS.SDO_ELEM_INFO_ARRAY(1,2,1),MDSYS.SDO_ORDINATE_ARRAY(-816008.5,-1071166.1,-815846.4,-1071166.1))

Similarly in conjunction with the Google Maps transform above:

  1. SELECT RoundOrdinates(
  2.             sdo_cs.transform(sdo_geometry(2002,8311,NULL,
  3.                                           sdo_elem_info_array(1,2,1),
  4.                                           sdo_ordinate_array(147.123,-32.456,147.672,-33.739)),3785),
  5.             1) AS geom
  6.   FROM dual;
  7. -- Results
  8. --
  9. GEOM
  10. --------------------------------------------------------------------------------------------------------
  12.                                   MDSYS.SDO_ORDINATE_ARRAY(16377657.4,-3800381.8,16438771.8,-3970070.5))


I have had a suggested change from a reader which is very clever. The clever idea used is:

We use to change the precision to “mm” (fix), so we hope to speed up the function by BULK COLLECT into a decreased precision array, instead of rounding rwo by row…

Here is the approach as an anonymous block (I changed some of the ordinate values to display the rounding):

  4.    sdoa3 SDO_ORDINATE_ARRAY3;
  6.                                       SDO_ELEM_INFO_ARRAY(1,2,1),
  7.                                       SDO_ORDINATE_ARRAY(3310000.12345,5620000.12345, 3310010.3456789,5620000.23456789));
  8. BEGIN
  9.   SELECT x.column_value BULK COLLECT
  10.     INTO sdoa3
  11.     FROM TABLE(tg.sdo_ordinates) x;
  12.   FOR i IN sdoa3.FIRST .. sdoa3.LAST
  13.   LOOP
  14.     dbms_output.put_line('SDO3('||i||')='||sdoa3(i));
  15.   END LOOP;
  16. END;
  17. /
  18. -- Results
  19. anonymous block completed
  20. SDO3(1)=3310000.123
  21. SDO3(2)=5620000.123
  22. SDO3(3)=3310010.346
  23. SDO3(4)=5620000.235

A few comments on this approach.

Speed: I expect that it will perform faster than my longer, pure PL/SQL approach but I have not yet tested it. (Perhaps another day.)

Parameterisation: When put into a function with the rounding value being a parameter, one cannot declare the reduced precision array using a parameter as can be seen in the following code:

  1. CREATE FUNCTION roundOrdinates(p_geom sdo_geometry, p_round_value pls_integer)
  2. RETURN sdo_geometry deterministic
  3. AS
  4.    v_round_value pls_integer := 3;
  5.    TYPE  SDO_ORDINATE_ARRAY3 IS VARRAY(1048576) OF NUMBER(11,v_round_value);
  6.   ...
  7. Error report:
  8. ORA-06550: line 6, COLUMN 62:
  9. PLS-00491: NUMERIC literal required
  10. 06550. 00000 -  "line %s, column %s:\n%s"
  11. *Cause:    Usually a PL/SQL compilation error.

Flexible Rounding: Following on from the previous point, the suggested approach does not allow the application of different rounding values for X, Y or Z. One cannot use the BULK COLLECTINTO reduced precision array trick. Though it has the benefit of the ability to write straight back to an sdo_geometry compliant sdo_ordinate_array as follows.

  3.    v_dims    pls_integer;
  4.    v_x_round pls_integer := 3;
  5.    v_y_round pls_integer := 2;
  6.    v_z_round pls_integer := 1;
  7.    sdoa  SDO_ORDINATE_ARRAY;
  9.                                       SDO_ELEM_INFO_ARRAY(1,2,1),
  10.                                       SDO_ORDINATE_ARRAY(3310000.12345,5620000.12345, 3310010.3456789,5620000.23456789));
  11. BEGIN
  12.   v_dims := tg.get_dims();
  13.   SELECT CASE MOD(rownum,v_dims)
  14.               WHEN 0 THEN ROUND(x.column_value,v_x_round)
  15.               WHEN 1 THEN ROUND(x.column_value,v_y_round)
  16.               WHEN 2 THEN ROUND(x.column_value,v_z_round)
  17.           END
  18.     BULK COLLECT
  19.     INTO sdoa
  20.     FROM TABLE(tg.sdo_ordinates) x;
  21.   FOR i IN sdoa.FIRST .. sdoa.LAST
  22.   LOOP
  23.     dbms_output.put_line('SDO('||i||')='||sdoa(i));
  24.   END LOOP;
  25. END;
  26. /
  27. -- Results
  28. anonymous block completed
  29. SDO(1)=3310000.12
  30. SDO(2)=5620000.123
  31. SDO(3)=3310010.35
  32. SDO(4)=5620000.235

I hope that either my function and/or the user suggested trick will be useful to someone.

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