Go to content Go to navigation and search


Current Oracle Spatial Blog Articles

    Using Oracle's ST_GEOMETRY type hierarchy with SDO_GEOMETRY: ST_PointN and ST_NumPoints
    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
    Writing Excel Spreadsheets files from within the Oracle database using Java and PL/SQL
    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
    Handy way of systematically fixing polygon geometries with 13349 and other errors
    Standalone CENTROID package now available for download
    Free Union, Intersection, Xor and Difference Functions for Oracle Locator - Part 4 Processing Geodetic data
    Configurable Buffer: JTS and Oracle
    Free Union, Intersection, Xor and Difference Functions for Oracle Locator - Part 3
    Free Union, Intersection, Xor and Difference Functions for Oracle Locator - Part 2
    Free Union, Intersection, Xor and Difference Functions for Oracle Locator - Part 1
    Building Lines into Polygons in Oracle Locator / Spatial
    Finding Intersection Points between Line and Polygon
    Free version of sdo_length
    Alternative to my SQL based GetNumRings function
    External Tables and SDO_Geometry data.
    layer_gtype keyword issue when indexing linear data on 11g
    String Tokenizer for Oracle
    Free Aggregate Method for Concatenating 2D Lines in Oracle Locator 10g
    Reducing 5 Vertex Polygon to Optimized Rectangle
    Square Buffer
    Converting decimal seconds to string
    Valid conversion unit values for Oracle sdo_geom.sdo_length()
    Removing Steps in Gridded Vector Data - SmoothGrid for Oracle
    Oracle Spatial DISJOINT search/filtering
    Creating SDO_Geometry from geometric data recorded in the columns of a table
    Concave Hull Geometries in Oracle 11gR2
    Projecting SDO_GEOM_METADATA DIMINFO XY ordinates
    Instantiating MDSYS.VERTEX_TYPE
    New PL/SQL Packages - Rotate oriented point
    GeoRaptor Development Team
    Fast Refreshing Materialized View Containing SDO_GEOMETRY and SDO_GEOM.SDO_AREA function
    Performance of PL/SQL Functions using SQL vs Pure Code
    Implementing the BEST VicGrid Projection in Oracle 10gR2
    ORA-13011 errors when using SDO_GEOM.VALIDATE_LAYER_WITH_CONTEXT()
    Extract Polygons from Compound Polygon
    Detecting sdo_geometries with compound (3-point Arcs) segments
    GEOMETRY_COLUMNS for Oracle Spatial
    Convert GML to SDO_Geometry in Oracle 10gR2
    Spatial Sorting of Data via Morton Key
    Swapping Ordinates in an SDO_GEOMETRY object
    New To_3D Function
    Extend (Reduce/Contract/Skrink) Function for Oracle
    Loading and Processing GPX 1.1 files using Oracle XMLDB
    Loading Spatial Data from an external CSV file in Oracle
    Calling the Oracle Spatial shapefile loader from within the Oracle database itself
    Implementing SDO_VertexUpdate/ST_VertexUpdate for Oracle
    Implementing SDO_RemovePoint/ST_RemovePoint for Oracle
    Implementing SDO_AddPoint/ST_AddPoint for Oracle
    ESRI ArcSDE Exverted and Inverted Polygons and Oracle Spatial
    Funky Fix Ordinates By Formula
    Implementing a SetPoint/ST_SetPoint function in Oracle
    Implementing an ST_SnapToGrid (PostGIS) function for Oracle Spatial
    Generating random point data
    Implementing an Affine/ST_Affine function for Oracle Spatial
    Implementing a Scale/ST_Scale function for Oracle Spatial
    Implementing a Parallel/ST_Parallel function for linestring data for Oracle Spatial
    Implementing a Rotate/ST_Rotate function for Oracle Spatial
    Limiting table list returned when connecting to Oracle Database using ODBC
    ST_Azimuth for Oracle: AKA Cogo.Bearing
    Implementing a Translate/ST_Translate/Move function for Oracle Spatial
    Elem_Info_Array Processing: An alternative to SDO_UTIL.GetNumRings and querying SDO_ELEM_INFO itself
    Minumum Bounding Rectangle (MBR) Object Type for Oracle
    How to extract elements from the result of an sdo_intersection of two polygons.
    How to restart a database after failed parameter change
    Fixing failed spatial indexes after import using data pump
    generate_series: an Oracle implementation in light of SQL Design Patterns
    Multi-Centroid Shootout
    Oracle Spatial Centroid Shootout
    On the use of ROLLUP in Oracle SELECT statements
    Surrounding Parcels
    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



RSS / Atom

Email me


Creative Commons License
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.

A simple spike finder for Spatial/Locator

Tuesday October 11 2011 at 23:35

When investigating geometric or topological errors for linear or polygonal geometry objects, a range of tools are needed. Oracle has basic tools which can be used as the building blocks for additional tests. These are:

One test that is not clearly provided for is the discovery of “spikes” in the linestring defining an outer or inner ring of a polygon (or any linestring).

Dictionary definitions of a spike include:

1. a naillike fastener, 3 to 12 inches (7.6 to 30.5 cm) long and proportionately thicker than a common nail, for fastening together heavy timbers or railroad track.
2. something resembling such a nail; a stiff, sharp-pointed piece or part: to set spikes in the top of a cement wall.
3. a sharp-pointed piece of metal set with the point outward, as on a weapon.
4. an abrupt increase or rise: a chart showing a spike of unusual activity in the stock market; a sudden spike of electrical current.
5. a rectangular or naillike metal projection on the heel and sole of a shoe for improving traction, as of a baseball player or a runner.

9. a pointed portion of a continuous curve or graph, usually rising above the adjacent portion: a spike in the value of the voltage.

Applying these to geographic/geometric linear objects we could say that a “spike” is:

is a sharp, abrupt and narrow deviation from the normal course of a linestring


However, in the context of this article, the spike being discussed is in no way related to Mr Milligan!:

How can we detect spikes?

One simple (the point of this article) method for finding a spike is to see if the gap between the two “vectors” that compose the spike collapse at the specified tolerance of a table’s geometry column (user_sdo_geom_metadata) causing a topological error (often 13349). Here are two examples of spikes.

Spike 1 Spike 2

A simple algorithm for finding spikes is to walk all the adjacent “vectors” of a linestring and send each pair into SDO_GEOM.RELATE with a “determine” mask. If the result is anything other than TOUCH we must have an error.

  1.    /** ----------------------------------------------------------------------------------------
  2.     * @function   : FindSpikes
  3.     * @precis     : Function that implements a simple "spike" finder.
  4.     * @version    : 1.0
  5.     * @usage      : SELECT b.* FROM test a, TABLE(FindSpikes(a.geom,0.005) b;
  6.     * @param      : p_geometry  : MDSYS.SDO_GEOMETRY : An sdo_geometry line or polygon object.
  7.     * @param      : p_tolerance : NUMBER             : Oracle sdo_tolerance value eg 0.005 meters for geodetic.
  8.     * @history    : Simon Greener - October 2011 - Original coding.
  9.     * @copyright  : Licensed under a Creative Commons Attribution-Share Alike 2.5 Australia License.
  10.     *               http://creativecommons.org/licenses/by-sa/2.5/au/
  11.    **/
  13.    FUNCTION FindSpikes(p_geometry    IN mdsys.sdo_geometry,
  14.                        p_tolerance   IN NUMBER DEFAULT 0.005)
  15.     RETURN CODESYS.SDO_ERROR.T_VectorSet pipelined
  16.   AS
  17.     v_vector       CODESYS.t_vector;
  18.     v_vectors      CODESYS.SDO_ERROR.T_VectorSet;
  19.     v_num_elements pls_integer;
  20.     v_element_no   pls_integer;
  21.     v_element      mdsys.sdo_geometry;
  22.     v_num_rings    pls_integer;
  23.     v_ring_no      pls_integer;
  24.     v_ring         mdsys.sdo_geometry;
  25.     v_relate       varchar2(100);
  28.   BEGIN
  29.      IF ( p_geometry IS NULL ) THEN
  30.        Raise NULL_GEOMETRY;
  31.      ElsIf ( p_geometry.get_gtype() NOT IN (2,5,3,7) ) THEN
  32.         RAISE NOT_LINE_POLY;
  33.      END IF;
  34.      -- Process Line/Multiline and Polygon/Multipolygon
  35.      --
  36.      v_num_elements := MDSYS.SDO_UTIL.GETNUMELEM(p_geometry);
  37.      <<Process_All_Elements>>
  38.      FOR v_element_no IN 1..v_num_elements LOOP
  39.          v_element := MDSYS.SDO_UTIL.EXTRACT(p_geometry,v_element_no,0);
  40.          IF ( v_element IS NOT NULL ) THEN
  41.              -- Polygons
  42.              -- Need to check for inner rings
  43.              --
  44.              IF ( v_element.get_gtype() = 3) THEN
  45.                 -- Process all rings in this single polygon have?
  46.                 v_num_rings := GetNumRings(v_element);
  47.                 <<All_Rings>>
  48.                 FOR v_ring_no IN 1..v_num_rings LOOP
  49.                     v_ring            := MDSYS.SDO_UTIL.EXTRACT(p_geometry,v_element_no,v_ring_no);                    
  50.                     -- Now walk ring's vectors
  51.                     --
  52.                     IF ( v_ring IS NOT NULL ) THEN
  53.                        -- Process 1st/2rd vectors looking for spike
  54.                       SELECT CODESYS.T_Vector(v.id,V.Startcoord,V.Endcoord) AS vector
  55.                         BULK COLLECT INTO V_Vectors
  56.                         FROM TABLE(CODESYS.Sdo_Error.GetVector(v_ring)) V
  57.                        ORDER BY v.id;
  58.                       IF NOT ( V_Vectors IS NULL OR V_Vectors.COUNT = 0 ) THEN
  59.                          FOR I IN V_Vectors.FIRST..V_Vectors.LAST Loop
  60.                              IF ( i = V_Vectors.LAST ) THEN
  61.                                  v_vector := v_vectors(1);
  62.                              ELSE
  63.                                  v_vector := v_vectors(i+1);
  64.                              END IF;
  65.                              -- Check if the interact in a way other than TOUCH
  66.                              --
  67.                              v_relate := mdsys.sdo_geom.relate(Vector2Geom(v_vectors(i),p_geometry.sdo_srid),'DETERMINE',Vector2Geom(v_vector,p_geometry.sdo_srid),p_tolerance);
  68.                              IF ( v_relate <> 'TOUCH' ) THEN
  69.                                 PIPE ROW ( CODESYS.T_Vector(v_vectors(i).id,v_vectors(i).startCoord,v_vectors(i).endCoord)  );
  70.                                 PIPE ROW ( CODESYS.T_Vector(v_vector.id,v_vector.startCoord,v_vector.endCoord) );
  71.                              END IF;
  72.                          END Loop;
  73.                       END IF;
  74.                     END IF;
  75.                 END LOOP All_Rings;
  76.              -- Linestrings
  77.              --
  78.              ElsIf ( v_element.get_gtype() = 2) THEN
  79.                    -- Process 1st/2rd vectors looking for spike
  80.                   SELECT CODESYS.T_Vector(v.id,V.Startcoord,V.Endcoord) AS vector
  81.                     BULK COLLECT INTO V_Vectors
  82.                     FROM TABLE(CODESYS.Sdo_Error.GetVector(v_element)) V
  83.                    ORDER BY v.id;
  84.                   IF NOT ( V_Vectors IS NULL OR V_Vectors.COUNT = 0 ) THEN
  85.                      FOR I IN V_Vectors.FIRST..(V_Vectors.Last-1) Loop
  86.                          v_vector := v_vectors(i+1);
  87.                          -- Check if the interact in a way other than TOUCH
  88.                          --
  89.                          v_relate := mdsys.sdo_geom.relate(Vector2Geom(v_vectors(i),p_geometry.sdo_srid),'DETERMINE',Vector2Geom(v_vector,p_geometry.sdo_srid),p_tolerance);
  90.                          IF ( v_relate <> 'TOUCH' ) THEN
  91.                              PIPE ROW ( CODESYS.T_Vector(v_vectors(i).id,v_vectors(i).startCoord,v_vectors(i).endCoord)  );
  92.                              PIPE ROW ( CODESYS.T_Vector(v_vector.id,v_vector.startCoord,v_vector.endCoord) );
  93.                          END IF;
  94.                      END Loop;
  95.                   END IF;            
  96.              END IF;
  97.          END IF;
  98.      END LOOP;
  99.     RETURN ;
  100.     EXCEPTION
  102.         raise_application_error(c_i_null_geometry, c_s_null_geometry,TRUE);
  103.         RETURN;
  105.         raise_application_error(c_i_not_line_poly,   c_s_not_line_poly,TRUE);
  106.        RETURN ;
  107.   END FindSpikes;

Applying this function to the two spikes above we get.

Linestring with Spike 1 Linestring with Spike 2

I hope this is of use to someone.

Creative Commons License

post this at del.icio.uspost this at Diggpost this at Technoratipost this at Redditpost this at Farkpost this at Yahoo! my webpost this at Windows Livepost this at Google Bookmarkspost this to Twitter

Comment [1]

Hi Simon;

I try to compile your ‘FindSpikes’, but get the following errors:

[Error] PLS-00201 (14: 12): PLS-00201: ‘GREG2.SDO_ERROR’ must be declared (this one actually complained about ‘greg2.SDO_ERROR.T_VectorSet’. I don’t have CODESYS in my 11.2 db, but I do have the ‘GEOM’ package, so I changed ‘GREG2.SDO_ERROR’ to ‘GREG2.GEOM’ and this one error was gone, allowing the rest to appear:)
[Error] PLS-00201 (66: 64): PLS-00201: ‘VECTOR2GEOM’ must be declared
[Error] PLS-00201 (66: 64): PLS-00201: ‘VECTOR2GEOM’ must be declared
[Error] PLS-00201 (101: 33): PLS-00201: ‘C_I_NULL_GEOMETRY’ must be declared
[Error] PLS-00201 (104: 33): PLS-00201: ‘C_I_NOT_LINE_POLY’ must be declared

Your guidance would be much appreciated…

PS1: I had quite a few difficulties in installing your packages (had to eventually bypass the install.bat and do it manually), so I’ve undertaken the task to attempt to correct it and send it to you – fingers crossed.

PS2: I’m also a GeoRaptor addict. I hope, and wish, that the project will not go down the drain!

Gregory Stefanakos 7 February 2012, 16:17 #