Go to content Go to navigation and search

Home

Current Oracle Spatial Blog Articles

    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
    Implementation Of Travelling Salesman Problem
    Create Polygon From Bearings And Distances
    Function That Returns a Compass Point From a Whole Circle Bearing
    Playing around with Centroids by using different seed values
    GeoRaptor 4.x Update 2
    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
    Applying And Extending Oracle Spatial - Book Released
    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
    Useful Package of Wrapper Functions for Sdo_Util.AffineTransforms
    Compute Location from known Lat/Long point using delta easting and northing in miles
    SDO_AGGR_SET_UNION
    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
    SDO2GeoJSON
    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
    SDO_GEOM.VALIDATE_GEOMETRY_WITH_CONTEXT - 13356 Issues
    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
    Making Sdo Geometry Metadata Update Generic Code
    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

Search

    Browse

RSS / Atom

Email me

textpattern

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.

Loading and Processing GPX 1.1 files using Oracle XMLDB

Friday March 06 2009 at 06:21

There are a large number of geospatial data storage, delivery and interchange formats around nowadays. Including (I limit this discussion to vector data formats only):

  • Geography Markup Language (GML)
  • Keyhole Markup Language
  • GPS eXchange Format (GPX)
  • Vector Markup Language (VML)
  • Scalable Vector Graphics (SVG)
  • Victorian Government’s (Aust) Incremental Update Format (IUF)
  • New South Wales Government’s (Aust) Spatial Data Exchange (“SIX”) (and XML incremental update data stream)
  • LandXML
  • X3D (successor to Virtual Reality Modelling Language – VRML)

Each has multiple versions and the list do including all the GML Application Schemas like Geoscience Markup Language (GeoSciML), CityGML, LandGML, Climate Science Modelling Language (CSML) etc.

So what does all this mean? Certainly that the use of XML for geospatial purposes is firmly in place and likely to increase rather than decrease. And for the Oracle Spatial data practitioner? That they are, inevitably, be exposed to these formats and the need to load new, and update existing, Sdo_Geometry based data.

Over on Oracle Technet’s Spatial forum a user asked the following question :

“I have a GPX data that is XML based I know about FME and convert to shape then to oracle spatial, But what I want exactly to develop a small J2EE application to read the data from GPX file then load the data to database direct without third party software. Please if any one knows how to do it please help me.”

Now, this question cuts to the nub of the alternate way of approaching the processing of geospatial data. Why use an external, geospatial specific, tool when there are perfectly good, generic, integrated tools to do a job? The issues with using external tools are:

  • Need for a separately installed and configured tool either on the same server as the database (frowned upon in most organisations) – why purchase/install a separate tool if the existing database has the functionality?;
  • Cost of purchasing/learning external tool;
  • Need to re-test integration as external tool is upgraded (eg version 1 to version 2);
  • Need for specific expertise in a tool other than the database – what happens if the external tool specialist – who has written a special (idiosyncratic) script (in a non standard language) to implement the load/update – goes on leave or leaves the organisation entirely and the load script fails?;
  • Need for network/database connection – if the external application is on a separate server (or client PC) then a network connection is required when inserting/updating. If a batch process (via crontab or Windows Sheduled Task), what happens if the network goes down?

A lot of these issues are real as I have experienced them myself over the years as a consultant, a GIS Manager and an IT programmer.

Because all the above formats are XML, and Oracle Database (and its competitors) support XML processing inside the database, I thought I would write a short article on loading a GPX 1.1 file into Oracle and then extracting and generating Sdo_Geometry objects from it.

While I have given a presentation on the use of Oracle’s XMLDB before, I have not written a blog article showing, step by step, how to process a GPX file. Here is the article.

Instance Data and Schema

Firstly, the instance dataset. Late last year i downloaded GPX2SHP. Included with it is a file, pinatest2.gpx. This file forms the basis of my work.

Secondly, the GPX file is based on verison 1.1 of an XML Schema which was designed and is hosted by
Topographix. I downloaded and stored this xsd file with my GPX file.

Lots of programs support GPX and there are lots of examples of GPX instance documents available on the web. One source documenting programs and data is at the GISWiki.

There are other sample instance documents at the actual Topographix website but I chose not to use them as some include more complex extensions (which I didn’t want “clouding” the simplicity of this article) or were for GPX version 1.0 (the person asking the question on the Oracle forum has a version 1.1 document).

After having processed the GPX2SHP GPX file I found a great GPX document on the 2005 Tour de France. I wish I had found it earlier as it looks like a great dataset to process (except it too has a lot of complicating extensions holding additional data)!

Checking the data

One of the things about XML data is that often it is constructed informally (no XML Schema or Document Type Definition – DTD ) or is constructed and not checked against its XML Schema in order to ensure validity. Since I will be loading the data using XMLDB’s schema validation capabilties I thought I had best check the dataset I would be using. For this I used Altova’s XMLSpy 2009.

When I opened the pinatest2.gpx document in XMLSpy and validated it, XMLSpy indicated a range of errors in the document.

  1. The metadata section was incorrectly organised
  2. The WayPoint (wpt), Track (trk) and Route (rte) data were incorrectly ordered.

The metadata had to be corrected as follows.

MetadataBefore

	<metadata>
		<name>Manila to Mt. Pinatubo</name>
		<copyright>Toshihiro Hiraoka</copyright>
		<author>Toshihiro Hiraoka</author>
		<keyword>Manila Mt. Pinatubo gpx2shp</keyword>
		<link>http://gpx2shp.sourceforge.jp</link>
		<description>This is test data for gpx2shp.</description>
		<time>2004-12-29T08:23:55Z</time>
	</metadata>

MetadataAfter

	<metadata>
		<name>Manila to Mt. Pinatubo</name>
		<desc>This is test data for gpx2shp.</desc>
		<copyright author="Toshihiro Hiraoka">
			<year>2004</year>
			<license>http://gpx2shp.sourceforge.jp</license>
		</copyright>
		<link href="http://gpx2shp.sourceforge.jp">
			<text>Toshihiro Hiraoka</text>
		</link>
		<time>2004-12-29T08:23:55</time>
		<keywords>Manila Mt. Pinatubo gpx2shp</keywords>
		<bounds maxlat="90.0" maxlon="179.9" minlat="-90.0" minlon="-180.0"/>
	</metadata>

The ordering of the geospatial components in the original file was:

<gpx ....>
  <metadata>
  <trk>
  <rte>
  <wpt>
</gpx>

Whereas, the XML Schema requires the following order:

<gpx ....>
  <metadata>
  <wpt>
  <rte>
  <trk>
</gpx>

After correction I saved the file to a new name called gpxtest.gpx which you can download from this website.

Loading in to Oracle

After having corrected the GPX file I then proceeded to load it in to Oracle.

First off I needed to grant my schema some additional privileges:

connect system/******@gisdb
grant XDBADMIN to gis;
grant alter session to gis;

Then I need to create an Oracle Directory so that I can access and load the GPX instance data and schema.

connect gis/*****@gisdb
CREATE DIRECTORY gpxdir AS 'E:\BlogBits\TipsTricks\GPX';
GRANT READ ON gpxdir TO PUBLIC;

While not strictly speaking needed, the following function I have found useful as a simple method of loading XML documents from a file in a directory easier.

create or replace function getClobDocument(
    p_directoryname In varchar2,
    p_filename      In varchar2,
    p_charset       In varchar2 default NULL)
    return          CLOB deterministic
is
  v_file          bfile := bfilename(p_directoryname,p_filename);
  v_charContent   CLOB := ' ';
  v_targetFile    bfile;
  v_lang_ctx      number := DBMS_LOB.default_lang_ctx;
  v_charset_id    number := 0;
  v_src_offset    number := 1 ;
  v_dst_offset    number := 1 ;
  v_warning       number;
begin
  if p_charset is not null then
    v_charset_id := NLS_CHARSET_ID(p_charset);
  end if;
  v_targetFile := v_file;
  DBMS_LOB.fileopen(v_targetFile, DBMS_LOB.file_readonly);
  DBMS_LOB.LOADCLOBFROMFILE(v_charContent, 
                            v_targetFile,
                            DBMS_LOB.getLength(v_targetFile), 
                            v_src_offset, 
                            v_dst_offset,
                            v_charset_id, 
                            v_lang_ctx,
                            v_warning);
  DBMS_LOB.fileclose(v_targetFile);
  return v_charContent;
end;
/

Before loading our GPX XML data we need to register the XML Schema that describes the XML content using DBMS_XMLSCHEMA.REGISTERSCHEMA. This is done via a two-step process of creating a resource and then registering the actual schema.

-- Create some useful variable for use in the whole script
var schemaURL varchar2(256)
var schemaDoc varchar2(256)

begin
  :schemaURL := 'http://www.topografix.com/GPX/1/1/gpx.xsd';
  :schemaDoc := 'gpx.xsd';
end;
/

declare
  xmlSchema xmlType;
  res       boolean;
begin
  xmlSchema := XMLTYPE(getCLOBDocument('GPXDIR',:schemaDoc,'AL32UTF8'));
  if (dbms_xdb.existsResource(:schemaDoc)) then
      dbms_xdb.deleteResource(:schemaDoc);
  end if;
  res := dbms_xdb.createResource(:schemaDoc,xmlSchema);
end;
/

-- May not exist, but attempt to delete anyway.
execute dbms_xmlSchema.deleteSchema(:schemaURL,DBMS_XMLSCHEMA.DELETE_CASCADE_FORCE);

-- Now register the schema
begin
  dbms_xmlschema.registerSchema
  (
    :schemaURL,
    XMLTYPE(getCLOBDocument('GPXDIR',:schemaDoc,'AL32UTF8')),
    TRUE,TRUE,FALSE,FALSE
  );
end;
/

-- Queries to see if it exists
select * 
  from user_xml_schemas
 where schema_url = :schemaURL;

SCHEMA_URL                                LOCAL SCHEMA      INT_OBJNAME                QUAL_SCHEMA_URL                                                            HIER_TYPE   
----------------------------------------- ----- ----------- -------------------------- -------------------------------------------------------------------------- ---------
http://www.topografix.com/GPX/1/1/gpx.xsd YES   SYS.XMLTYPE XD79rS1GmSRMqW2gvRg8ufhQ== http://xmlns.oracle.com/xdb/schemas/GIS/www.topografix.com/GPX/1/1/gpx.xsd CONTENTS

1 rows selected

SELECT PATH,
       extract(LINK, 
               '/LINK/Name/text()').getstringval() as linkName,
       extract(LINK,
               '/LINK/ParentName/text()').getstringval() as ParentName,
       extract(LINK,
               '/LINK/ChildName/text()').getstringval() as ChildName,
       extract(RES, 
               '/Resource/DisplayName/text()').getstringval() as DisplayName
  FROM PATH_VIEW
 WHERE PATH like '/sys/schemas/GIS/www.topo%';

PATH                                                LINKNAME           PARENTNAME         CHILDNAME          DISPLAYNAME
--------------------------------------------------- ------------------ ------------------ ------------------ ------------------
/sys/schemas/GIS/www.topografix.com                 www.topografix.com GIS                www.topografix.com www.topografix.com 
/sys/schemas/GIS/www.topografix.com/GPX             GPX                www.topografix.com GPX                GPX
/sys/schemas/GIS/www.topografix.com/GPX/1           1                  GPX                1                  1
/sys/schemas/GIS/www.topografix.com/GPX/1/1         1                  1                  1                  1 
/sys/schemas/GIS/www.topografix.com/GPX/1/1/gpx.xsd gpx.xsd            1                  gpx.xsd            gpx.xsd 

5 rows selected

Now that the schema is loaded and registered, we can create a table to hold the GPX XML data. (I will not discuss the different types of XML storage that XMLDB provides, sufficeth to say that we will create a table of XMLType object type. That is, we will create an object-table.)

Prompt Create table to hold the sample GPX document
drop table GPX;

CREATE TABLE gpx
    OF XMLType 
    XMLSCHEMA "http://www.topografix.com/GPX/1/1/gpx.xsd" ELEMENT "gpx";

-- Now we can load the data itself
INSERT INTO GPX 
       VALUES (XMLTYPE(getCLOBDocument('GPXDIR','gpxtest.gpx')));
commit;

Additional Editing

When loading XML data into a table attributed with its XMLSCHEMA using the above, XMLDB will validate the data as it is loaded. The first-time I loaded the data Oracle XMLDB informed me that

ORA-01830: date format picture ends before converting entire input string xsd:dateTime

Upon investigation, the GPX file contains dateTime values like the following:

<time>2004-12-29T08:23:55Z</time>

With Schema-based XML with nodes of type xsd:dateTime, if an instance document contains dates with TimeZone information (ie the “Z” at the end of the time value above), then the XML schema must be annotated with xsd:SQLType=“TIMESTAMP WITH TIME ZONE” in order to tell XMLDB to expect Time Zone info.

While this is not that difficult to do it would entail changing both the XSD and XML. Something I don’t think my readers would want to do to their GPX documents. So, in order to get around XMLDB I simply removed the “Z” suffix from the end of all time values in the GPX document.

Checking the table creation and load we get.

select *
  from user_xml_tables 
 where table_name = 'GPX';

TABLE_NAME XMLSCHEMA                                 SCHEMA_OWNER ELEMENT_NAME  STORAGE_TYPE
---------- ----------------------------------------- ------------ ------------- -----------------
GPX        http://www.topografix.com/GPX/1/1/gpx.xsd GIS          gpx           OBJECT-RELATIONAL

1 rows selected

And, an additional check of the validity of the loaded XML shows all is well.

SELECT XMLIsValid(g.OBJECT_VALUE,'http://www.topografix.com/GPX/1/1/gpx.xsd') 
  FROM gpx g;

XMLISVALID(G.OBJECT_VALUE,'HTTP://WWW.TOPOGRAFIX.COM/GPX/1/1/GPX.XSD') 
---------------------------------------------------------------------- 
1                                                                      

1 rows selected

Note that it is possible to define the table to have a CHECk constraint as follows:

CREATE TABLE gpx
    OF XMLType 
   (CHECK (XMLIsValid(object_value) = 1))
    XMLSCHEMA "http://www.topografix.com/GPX/1/1/gpx.xsd" ELEMENT "gpx";

Querying

Let’s start our querying with a very simple request to see the name of the GPX file.

SELECT extractValue(g.object_value,'/gpx/metadata/name','xmlns="http://www.topografix.com/GPX/1/1"') metadataName
 FROM GPX g;

METADATANAME
-------------------------
Manila to Mt. Pinatubo

1 rows selected

Let’s now see the full metadata.

SELECT extractValue(g.object_value,'/gpx/metadata/name','xmlns="http://www.topografix.com/GPX/1/1"') as Name,
       extractValue(g.object_value,'/gpx/metadata/desc','xmlns="http://www.topografix.com/GPX/1/1"') as Description,
       extractValue(g.object_value,'/gpx/metadata/copyright/year','xmlns="http://www.topografix.com/GPX/1/1"') as Copyright_Year,
       extractValue(g.object_value,'/gpx/metadata/copyright/license','xmlns="http://www.topografix.com/GPX/1/1"') as Copyright_License,
       extractValue(g.object_value,'/gpx/metadata/link/@href','xmlns="http://www.topografix.com/GPX/1/1"') as Hyperlink,
       extractValue(g.object_value,'/gpx/metadata/link/text','xmlns="http://www.topografix.com/GPX/1/1"') as Hyperlink_Text,
       extractValue(g.object_value,'/gpx/metadata/time','xmlns="http://www.topografix.com/GPX/1/1"') as Document_DateTime,
       extractValue(g.object_value,'/gpx/metadata/keywords','xmlns="http://www.topografix.com/GPX/1/1"') as keywords,
       extractValue(g.object_value,'/gpx/metadata/bounds/@minlon','xmlns="http://www.topografix.com/GPX/1/1"') as MinLong,
       extractValue(g.object_value,'/gpx/metadata/bounds/@minlat','xmlns="http://www.topografix.com/GPX/1/1"') as MinLat,
       extractValue(g.object_value,'/gpx/metadata/bounds/@maxlon','xmlns="http://www.topografix.com/GPX/1/1"') as MaxLong,
       extractValue(g.object_value,'/gpx/metadata/bounds/@maxlat','xmlns="http://www.topografix.com/GPX/1/1"') as MaxLat
 FROM GPX g;

NAME                   DESCRIPTION                    COPYRIGHT_YEAR COPYRIGHT_LICENSE             HYPERLINK                     HYPERLINK_TEXT    DOCUMENT_DATETIME               KEYWORDS                    MINLONG MINLAT MAXLONG MAXLAT
---------------------- ------------------------------ -------------- ----------------------------- ----------------------------- ----------------- ------------------------------- --------------------------- ------- ------ ------- ------
Manila to Mt. Pinatubo This is test data for gpx2shp. 01/JAN/04      http://gpx2shp.sourceforge.jp http://gpx2shp.sourceforge.jp Toshihiro Hiraoka 29/DEC/04 08:23:55.000000000 AM Manila Mt. Pinatubo gpx2shp    -180    -90   179.9     90

1 rows selected

Now let’s extract our waypoints (only name and coordinates).

SELECT SUBSTR(EXTRACTVALUE(VALUE(t), 'wpt/name'),1,20) as Name,
       TO_NUMBER(EXTRACTVALUE(VALUE(t), 'wpt/@lon')) as longitude,
       TO_NUMBER(EXTRACTVALUE(VALUE(t), 'wpt/@lat')) as latitude,
       TO_NUMBER(EXTRACTVALUE(VALUE(t), 'wpt/ele'))  as Elevation
 FROM GPX g,
      TABLE(XMLSequence(extract(g.OBJECT_VALUE,'/gpx/wpt','xmlns="http://www.topografix.com/GPX/1/1"'))) t;

NAME                 LONGITUDE              LATITUDE               ELEVATION
-------------------- ---------------------- ---------------------- ----------
001                  121.043382715          14.636015547           45.307495
002                  121.042653322          14.637198653           50.594727
003                  121.043165457          14.640581002           46.989868
004                  120.155537082          14.975596117           38.097656
...
111                  120.917379661          14.474465596           5.172729
112                  120.938029736          14.942621375           28.965332
113                  124.379444299          12.255321192           21.995728
GARMIN               -94.799016668          38.855549991           325.049072
GRMEUR               -1.463899976           50.982883293           35.934692
GRMPHX               -111.946110008         33.330189949           361.098145
GRMTWN               121.640266674          25.061783362           38.097656
NEDA4                121.043607602          14.636060139           8.296997

118 rows selected

Since our target is SDO_Geometry let’s re-do the above query and make it generate Oracle Spatial data.

SELECT SUBSTR(EXTRACTVALUE(VALUE(t), 'wpt/name'),1,20) as Name,
       SDO_GEOMETRY(3001,
                    8307,
                    SDO_POINT_TYPE(TO_NUMBER(EXTRACTVALUE(VALUE(t), 'wpt/@lon')),
                                   TO_NUMBER(EXTRACTVALUE(VALUE(t), 'wpt/@lat')),
                                   TO_NUMBER(EXTRACTVALUE(VALUE(t), 'wpt/ele'))),
	            NULL,
		NULL) as geom
 FROM GPX g,
      TABLE(XMLSequence(extract(g.OBJECT_VALUE,'/gpx/wpt','xmlns="http://www.topografix.com/GPX/1/1"'))) t;

NAME                 GEOM
------ --------------------------------------------------------------------------------------------------
001    MDSYS.SDO_GEOMETRY(3001,8307,MDSYS.SDO_POINT_TYPE(121.043382715,14.636015547,45.307495),null,null)
002    MDSYS.SDO_GEOMETRY(3001,8307,MDSYS.SDO_POINT_TYPE(121.042653322,14.637198653,50.594727),null,null)
003    MDSYS.SDO_GEOMETRY(3001,8307,MDSYS.SDO_POINT_TYPE(121.043165457,14.640581002,46.989868),null,null)
004    MDSYS.SDO_GEOMETRY(3001,8307,MDSYS.SDO_POINT_TYPE(120.155537082,14.975596117,38.097656),null,null)
...
111    MDSYS.SDO_GEOMETRY(3001,8307,MDSYS.SDO_POINT_TYPE(120.917379661,14.474465596,5.172729),null,null)
112    MDSYS.SDO_GEOMETRY(3001,8307,MDSYS.SDO_POINT_TYPE(120.938029736,14.942621375,28.965332),null,null)
113    MDSYS.SDO_GEOMETRY(3001,8307,MDSYS.SDO_POINT_TYPE(124.379444299,12.255321192,21.995728),null,null)
GARMIN MDSYS.SDO_GEOMETRY(3001,8307,MDSYS.SDO_POINT_TYPE(-94.799016668,38.855549991,325.049072),null,null)
GRMEUR MDSYS.SDO_GEOMETRY(3001,8307,MDSYS.SDO_POINT_TYPE(-1.463899976,50.982883293,35.934692),null,null)
GRMPHX MDSYS.SDO_GEOMETRY(3001,8307,MDSYS.SDO_POINT_TYPE(-111.946110008,33.330189949,361.098145),null,null)
GRMTWN MDSYS.SDO_GEOMETRY(3001,8307,MDSYS.SDO_POINT_TYPE(121.640266674,25.061783362,38.097656),null,null)
NEDA4  MDSYS.SDO_GEOMETRY(3001,8307,MDSYS.SDO_POINT_TYPE(121.043607602,14.636060139,8.296997),null,null)

118 rows selected

Now waypoints are the bread and butter of most GPS use, but we also find tracks and sometimes routes. Both of these are linear elements so we need to see how to process them.

First, let’s look at the routes in the GPX file.

-- Show all routes
SELECT SUBSTR(   EXTRACTVALUE(VALUE(t1), 'rte/name'),1,10) as route_name,
       TO_NUMBER(EXTRACTVALUE(VALUE(t1), 'rte/number'))    as route_number
  FROM GPX g,
       TABLE(XMLSequence(extract(g.OBJECT_VALUE,'/gpx/rte','xmlns="http://www.topografix.com/GPX/1/1"'))) t1;

ROUTE_NAME ROUTE_NUMBER
---------- ------------
10-SEP-04  4

1 rows selected

-- Show the route and all its points (as XML)
SELECT SUBSTR(   EXTRACTVALUE(VALUE(t1), 'rte/name'),1,10) as route_name,
       TO_NUMBER(EXTRACTVALUE(VALUE(t1), 'rte/number'))    as route_number,
       EXTRACT(g.OBJECT_VALUE,'/gpx/rte/rtept','xmlns="http://www.topografix.com/GPX/1/1"') as route_pts
  FROM GPX g,
       TABLE(XMLSequence(extract(g.OBJECT_VALUE,'/gpx/rte[number=4]','xmlns="http://www.topografix.com/GPX/1/1"'))) t1;

ROUTE_NAME ROUTE_NUMBER           ROUTE_PTS
---------- ------------ ---------------------------------------------------------------------------------
10-SEP-04  4            <rtept xmlns="http://www.topografix.com/GPX/1/1" lat="15.044639" lon="120.25491">
                          <ele>209.704834</ele>
                          <time>2004-09-09T01:57:08.000000</time>
                        </rtept>
..
                        <rtept xmlns="http://www.topografix.com/GPX/1/1" lat="14.980567" lon="120.193627">
                          <ele>68.871582</ele>
                          <time>2004-09-10T00:51:48.000000</time>
                        </rtept>

1 rows selected

-- Finally, show the route with its point objects (same definition as a waypoint point object)
SELECT SUBSTR(   EXTRACTVALUE(VALUE(t1), 'rte/name'),1,10) as route_name,
       TO_NUMBER(EXTRACTVALUE(VALUE(t1), 'rte/number'))    as route_number,
       TO_NUMBER(EXTRACTVALUE(VALUE(t), 'rtept/@lon','xmlns="http://www.topografix.com/GPX/1/1"')) as longitude,
       TO_NUMBER(EXTRACTVALUE(VALUE(t), 'rtept/@lat','xmlns="http://www.topografix.com/GPX/1/1"')) as latitude,
       TO_NUMBER(EXTRACTVALUE(VALUE(t), 'rtept/ele','xmlns="http://www.topografix.com/GPX/1/1"')) as elevation
 FROM GPX g,
      TABLE(XMLSequence(extract(g.OBJECT_VALUE,'/gpx/rte[number=4]','xmlns="http://www.topografix.com/GPX/1/1"'))) t1,
      TABLE(XMLSequence(extract(g.OBJECT_VALUE,'/gpx/rte[number=4]/rtept','xmlns="http://www.topografix.com/GPX/1/1"'))) t;

ROUTE_NAME ROUTE_NUMBER LONGITUDE  LATITUDE   ELEVATION
---------- ------------ ---------- ---------- ----------
10-SEP-04  4            120.25491  15.044639  209.704834
10-SEP-04  4            120.25491  15.044446  206.340088
10-SEP-04  4            120.254931 15.044231  206.340088
10-SEP-04  4            120.255103 15.043373  207.782104
10-SEP-04  4            120.25506  15.04333   206.820679
.....
10-SEP-04  4            120.193799 14.980609  69.832886
10-SEP-04  4            120.193627 14.980567  68.871582

323 rows selected

Finally, let’s use some SQL trickery to turn this single route into a linear SDO_Geometry object.

-- Turn (Single) Route into geometry
SELECT mdsys.sdo_geometry(3002,8307,null,mdsys.sdo_elem_info_array(1,2,1),
CAST(MULTISET( 
 SELECT case when r.rin = 1 then longitude
             when r.rin = 2 then latitude
             when r.rin = 3 then elevation
         end as ordinate
   FROM (select level rin from dual connect by level < 4) r,
        (SELECT rownum as pt,
                TO_NUMBER(EXTRACTVALUE(VALUE(t), 'rtept/@lon','xmlns="http://www.topografix.com/GPX/1/1"')) as longitude,
                TO_NUMBER(EXTRACTVALUE(VALUE(t), 'rtept/@lat','xmlns="http://www.topografix.com/GPX/1/1"')) as latitude,
                TO_NUMBER(EXTRACTVALUE(VALUE(t), 'rtept/ele','xmlns="http://www.topografix.com/GPX/1/1"'))  as elevation
           FROM GPX g,
                TABLE(XMLSequence(extract(g.OBJECT_VALUE,'/gpx/rte/rtept','xmlns="http://www.topografix.com/GPX/1/1"'))) t
        ) x
   order by x.pt, r.rin
) AS mdsys.sdo_ordinate_array)) as geom
  FROM DUAL ;

GEOM
--------------------------------------------
MDSYS.SDO_GEOMETRY(3002,8307,null,
      MDSYS.SDO_ELEM_INFO_ARRAY(1,2,1),
      MDSYS.SDO_ORDINATE_ARRAY(
            120.25491,15.044639,209.704834,
            120.25491,15.044446,206.340088,
            120.254931,15.044231,206.340088,
            120.255103,15.043373,207.782104,
            120.25506,15.04333,206.820679,
            ...
            120.193799,14.980609,69.832886,
            120.193627,14.980567,68.871582))

1 rows selected

The above geometry (which also passed SDO_GEOM.VALIDATE_GEOMETRY testing) was edited to aid presentation as it contains 323 3D coordinates.

Note you cannot use SDO_AGGR_UNION with point objects to generate a linestring (change the 3005 to 2002 and change the SDO_ELEM_INFO_ARRAY). The reason is that, at 10gR2, the resultant aggregated points can only be 2D.

Now the above approach is fine if the file contains a single route: what if it contains many?

The GPX file I loaded contains a number of tracks. Let’s look at them.

-- Get all tracks
SELECT TO_NUMBER(EXTRACTVALUE(VALUE(t1), 'trk/number')) as track_number,
       SUBSTR(EXTRACTVALUE(VALUE(t1), 'trk/name'),1,10)  as track_name
  FROM GPX g,
       TABLE(XMLSequence(extract(g.OBJECT_VALUE,'/gpx/trk','xmlns="http://www.topografix.com/GPX/1/1"'))) t1;

TRACK_NUMBER           TRACK_NAME 
---------------------- ---------- 
1                      07-SEP-04  
2                      08-SEP-04  
3                      08-SEP-04  
7                      Only 5 poi 

4 rows selected

We have 4 tracks.

Now, tracks are organised a little differently than routes. Tracks can contain multiple segments (trkseg) each of which can have multiple points (trkpt).

-- Get each track's segments
SELECT TO_NUMBER(EXTRACTVALUE(VALUE(t1), 'trk/number')) as track_number,
       SUBSTR(EXTRACTVALUE(VALUE(t1), 'trk/name'),1,10)  as track_name,
       EXTRACT(g.OBJECT_VALUE,'/gpx/trk[number=' || EXTRACTVALUE(VALUE(t1), 'trk/number') || ']/trkseg','xmlns="http://www.topografix.com/GPX/1/1"') as trackSeg
  FROM GPX g,
       TABLE(XMLSequence(extract(g.OBJECT_VALUE,'/gpx/trk','xmlns="http://www.topografix.com/GPX/1/1"'))) t1;

TRACK_NUMBER           TRACK_NAME TRACKSEG 
---------------------- ---------- -----------------------------------------------------------------------------------------------------------------------------
1                      07-SEP-04  <trkseg xmlns="http://www.topografix.com/GPX/1/1"><trkpt lat="14.585381" lon="121.056118"><ele>42.916016</ele>  ... </trkseg>
2                      08-SEP-04  <trkseg xmlns="http://www.topografix.com/GPX/1/1"><trkpt lat="15.043309" lon="120.254095"><ele>206.340088</ele> ... </trkseg>
3                      08-SEP-04  <trkseg xmlns="http://www.topografix.com/GPX/1/1"><trkpt lat="15.043309" lon="120.254095"><ele>206.340088</ele> ... </trkseg>
7                      Only 5 poi <trkseg xmlns="http://www.topografix.com/GPX/1/1"><trkpt lat="14.907889" lon="120.558472"><ele>28.976929</ele>  ... </trkseg>

4 rows selected

Of course I have edited and truncated the trkseg data.

Now, let’s turn these tracks into linestring geometries.

-- Turn (Multiple) Tracks into geometry
-- Note, all can only have one track segment
-- (If more than one track segment would need to handle by generating more than one row per track and group output below by SDO_AGGR_UNION)
-- 
WITH tracks As (
SELECT TO_NUMBER(EXTRACTVALUE(VALUE(t1), 'trk/number')) as track_number,
       SUBSTR(EXTRACTVALUE(VALUE(t1), 'trk/name'),1,10)  as track_name,
       EXTRACT(g.OBJECT_VALUE,'/gpx/trk[number=' || EXTRACTVALUE(VALUE(t1), 'trk/number') || ']/trkseg','xmlns="http://www.topografix.com/GPX/1/1"') as trackSeg
  FROM GPX g,
       TABLE(XMLSequence(extract(g.OBJECT_VALUE,'/gpx/trk','xmlns="http://www.topografix.com/GPX/1/1"'))) t1
)
SELECT trk.track_number,
       trk.track_name,
       sdo_geom.validate_geometry(mdsys.sdo_geometry(3002,8307,null,sdo_elem_info_array(1,2,1),
       CAST(MULTISET(SELECT case when mod(rownum,3) = 1 then TO_NUMBER(EXTRACT(VALUE(t), '/trkpt/@lon','xmlns="http://www.topografix.com/GPX/1/1"'))
                                 when mod(rownum,3) = 2 then TO_NUMBER(EXTRACT(VALUE(t), '/trkpt/@lat','xmlns="http://www.topografix.com/GPX/1/1"'))
                                 when mod(rownum,3) = 0 then TO_NUMBER(EXTRACT(VALUE(t), '/trkpt/ele/text()','xmlns="http://www.topografix.com/GPX/1/1"'))
                             end ordinate
                       FROM (select level as rin from dual connect by level < 4) r,
                             TABLE(XMLSequence(EXTRACT(trk.trackSeg,'/trkseg/trkpt','xmlns="http://www.topografix.com/GPX/1/1"'))) t
                    ) as mdsys.sdo_ordinate_array
           )),0.05) as geom
  FROM tracks trk;

TRACK_NUMBER           TRACK_NAME GEOM
---------------------- ---------- ----
1                      07-SEP-04  TRUE
2                      08-SEP-04  TRUE
3                      08-SEP-04  TRUE
7                      Only 5 poi TRUE

4 rows selected

Luckily, each of these tracks only has one track segment. If a track had more than one track segment we would have to generate MULTILINESTRINGS and not LINESTRINGS. For me that was slightly more involved as I ran in difficulties pursuing an pure-SQL based approach.

MultiLineStrings

The above SQL works because it splits out each trkseg that is associated with a track via a separate line. One could use SDO_AGGR_UNION or SDO_AGGR_CONCAT_LINES on the resultant geometry objects but I have found, after modifying the above SQL with a suitable GROUP BY clause that I could not generate the correct answer with either spatial aggregate (the main problem is the generation of the SDO_ELEM_INFO_ARRAY).

In the end I decided that I would have to do the geometry generation myself.

Firstly, I modified the gpxtest.gpx file merging the last two tracks:

Tracks and SegmentsBefore

			<trkpt lat="15.044639" lon="120.254910">
				<ele>209.704834</ele>
				<time>2004-09-09T01:56:51</time>
			</trkpt>
		</trkseg>
	</trk>
	<trk>
		<name>Only 5 points</name>
		<number>7</number>
		<trkseg>
			<trkpt lat="14.907889" lon="120.558472">
				<ele>28.976929</ele>
				<time>2004-09-10T08:35:38</time>
			</trkpt>

Tracks and SegmentsAfter

			<trkpt lat="15.044639" lon="120.254910">
				<ele>209.704834</ele>
				<time>2004-09-09T01:56:51</time>
			</trkpt>
		</trkseg>
		<trkseg>
			<trkpt lat="14.907889" lon="120.558472">
				<ele>28.976929</ele>
				<time>2004-09-10T08:35:38</time>
			</trkpt>

Then I loaded the modified GPX file into a new table.

drop table GPX2;
purge recyclebin;
create table GPX2
    of xmltype
    XMLSCHEMA "http://www.topografix.com/GPX/1/1/gpx.xsd" ELEMENT "gpx";
INSERT INTO GPX2 VALUES (XMLTYPE(getCLOBDocument('GPXDIR','gpxtest2.gpx')));
commit;

Now let’s query out the number of segments per track.

SELECT TO_NUMBER(EXTRACTVALUE(VALUE(t1), 'trk/number')) as track_number,
       SUBSTR(EXTRACTVALUE(VALUE(t1), 'trk/name'),1,10)  as track_name,
       count(*) as segments
  FROM GPX2 g,
       TABLE(XMLSequence(EXTRACT(g.OBJECT_VALUE,'/gpx/trk','xmlns="http://www.topografix.com/GPX/1/1"'))) t1,
       TABLE(XMLSequence(EXTRACT(VALUE(t1),'trk[number=' || EXTRACTVALUE(VALUE(t1), 'trk/number') || ']/trkseg','xmlns="http://www.topografix.com/GPX/1/1"'))) t2
 GROUP BY TO_NUMBER(EXTRACTVALUE(VALUE(t1), 'trk/number')),
          SUBSTR(EXTRACTVALUE(VALUE(t1), 'trk/name'),1,10)  
 order by 1;

TRACK_NUMBER           TRACK_NAME SEGMENTS
---------------------- ---------- ----------------------
1                      07-SEP-04  1
2                      08-SEP-04  1
3                      08-SEP-04  2

3 rows selected

You will note that I have to make extensive use of standard SQL’s COUNT function while, in many cases, use of XPath’s COUNT function would be far neater. However, XMLDB does not support the XPath COUNT function at 10gR2. It is, however, supported at 11gR1.

Now, to generate a single geometry for all segments in a track one must, of course, ensure that the SDO_ELEM_INFO_ARRAY is correctly generated. I looked at different ways to do this in pure SQL but I could not get a base SQL statement that I could to extend to work. For example, the following SQL statement, which tries to use the CAST(MULTISET approach that worked successfully for generating the SDO_ORDINATE_ARRAY, simply refused to terminate. I could get elements of the SQL to work via a “divide-and-conquery” approach but I was thwarted at every turn.

-- This doesn't work as its execution never returns
WITH tracks As (
SELECT TO_NUMBER(EXTRACTVALUE(VALUE(t1), 'trk/number')) as track_number,
       SUBSTR(EXTRACTVALUE(VALUE(t1), 'trk/name'),1,10)  as track_name,
       (SELECT count(*)
          FROM TABLE(XMLSequence(EXTRACT(VALUE(t1),
                                         'trk[number=' || EXTRACTVALUE(VALUE(t1), 'trk/number') || ']/trkseg',
                                         'xmlns="http://www.topografix.com/GPX/1/1"')))) as SegCount,
       EXTRACT(VALUE(t1),
               'trk[number=' || EXTRACTVALUE(VALUE(t1), 'trk/number') || ']/trkseg',
               'xmlns="http://www.topografix.com/GPX/1/1"') as allSegments
  FROM GPX2 g,
       TABLE(XMLSequence(EXTRACT(g.OBJECT_VALUE,'/gpx/trk','xmlns="http://www.topografix.com/GPX/1/1"'))) t1
)
SELECT trk.track_number,
       trk.track_name,
       CASE WHEN trk.segcount = 1 
            THEN mdsys.sdo_elem_info_array(1,2,1) 
            ELSE 
       CAST(MULTISET(SELECT count(*)
                       FROM TABLE(codesys.geom.generate_series(1,trk.segCount,1)) gs,
                            TABLE(XMLSequence(EXTRACT(trk.allSegments,'/trkseg['||gs.column_value||']/trkpt','xmlns="http://www.topografix.com/GPX/1/1"'))) t
                      GROUP BY gs.column_value
                     ) AS mdsys.sdo_elem_info_array ) 
        END as coordarray,
       mdsys.sdo_geometry(3002,8307,null,
         mdsys.sdo_elem_info_array(1,2,1),
         /* mdsys.sdo_ordinate_array */
         CAST(MULTISET(SELECT case when mod(rownum,3) = 1 then TO_NUMBER(EXTRACT(VALUE(t), '/trkpt/@lon','xmlns="http://www.topografix.com/GPX/1/1"'))
                                   when mod(rownum,3) = 2 then TO_NUMBER(EXTRACT(VALUE(t), '/trkpt/@lat','xmlns="http://www.topografix.com/GPX/1/1"'))
                                   when mod(rownum,3) = 0 then TO_NUMBER(EXTRACT(VALUE(t), '/trkpt/ele/text()','xmlns="http://www.topografix.com/GPX/1/1"'))
                               end ordinate
                         FROM (select level as rin from dual connect by level < 4) r,
                               TABLE(XMLSequence(EXTRACT(trk.allSegments,'/trkseg/trkpt','xmlns="http://www.topografix.com/GPX/1/1"'))) t
                      ) as mdsys.sdo_ordinate_array
             )) as geom
  FROM tracks trk;
-- Does not terminate

In the end, I decided to encapsulate the SDO_ELEM_INFO_ARRAY processing into a PL/SQL Function.

CREATE OR REPLACE FUNCTION GetElemInfoFromXML ( p_trkseg_xml IN XMLType
) RETURN mdsys.Sdo_Elem_Info_Array 
AS
  v_seg_count number;
  v_array     mdsys.sdo_ordinate_array;
  v_elem_info mdsys.Sdo_Elem_Info_Array := new mdsys.Sdo_Elem_Info_Array(1,2,1);
BEGIN
  SELECT count(*)
    INTO v_seg_count
    FROM TABLE(XMLSequence(EXTRACT(p_trkseg_xml,
                                   'trkseg',
                                   'xmlns="http://www.topografix.com/GPX/1/1"')));
  If ( v_seg_count > 0 ) Then
    SELECT count(*)
      BULK COLLECT INTO v_array
      FROM TABLE(codesys.geom.generate_series(1,v_seg_count,1)) gs,
           TABLE(XMLSequence(EXTRACT(p_trkseg_xml,
                                             '/trkseg['||gs.column_value||']/trkpt',
                                             'xmlns="http://www.topografix.com/GPX/1/1"'))) t
     GROUP BY gs.column_value
     ORDER BY gs.column_value;
  
    IF ( v_array is not null AND v_array.COUNT > 1 ) THEN
      FOR i IN v_array.FIRST..(v_array.LAST-1) LOOP
        v_elem_info.EXTEND(3);
        v_elem_info(v_elem_info.COUNT-2) := ( v_array(i) * 3 ) + v_elem_info(v_elem_info.COUNT-5);
        v_elem_info(v_elem_info.COUNT-1) := 2;
        v_elem_info(v_elem_info.COUNT  ) := 1;
      END LOOP;
    END IF;
  END IF;
  RETURN v_elem_info;
END GetElemInfoFromXML;
/
show errors

Which I then used as follows:

SELECT TO_NUMBER(EXTRACTVALUE(VALUE(t1), 'trk/number')) as track_number,
       SUBSTR(EXTRACTVALUE(VALUE(t1), 'trk/name'),1,10)  as track_name,
       mdsys.sdo_geometry(CASE WHEN (SELECT COUNT(*) 
                                       FROM TABLE(XMLSequence(EXTRACT(VALUE(allSegments),
                                                                     'trk/trkseg',
                                                                     'xmlns="http://www.topografix.com/GPX/1/1"')))) > 1
                               THEN 3006
                               ELSE 3002
                           END,
                          8307,
                          NULL,
         GetElemInfoFromXML(EXTRACT(VALUE(allSegments),'trk/trkseg','xmlns="http://www.topografix.com/GPX/1/1"')),
         CAST(MULTISET(SELECT case when mod(rownum,3) = 1 then TO_NUMBER(EXTRACT(VALUE(t), '/trkpt/@lon','xmlns="http://www.topografix.com/GPX/1/1"'))
                                   when mod(rownum,3) = 2 then TO_NUMBER(EXTRACT(VALUE(t), '/trkpt/@lat','xmlns="http://www.topografix.com/GPX/1/1"'))
                                   when mod(rownum,3) = 0 then TO_NUMBER(EXTRACT(VALUE(t), '/trkpt/ele/text()','xmlns="http://www.topografix.com/GPX/1/1"'))
                               end ordinate
                         FROM (select level as rin from dual connect by level < 4) r,
                               TABLE(XMLSequence(EXTRACT(VALUE(allSegments),'trk/trkseg/trkpt','xmlns="http://www.topografix.com/GPX/1/1"'))) t
                      ) as mdsys.sdo_ordinate_array
             )) as geom
  FROM GPX2 g,
       TABLE(XMLSequence(EXTRACT(g.OBJECT_VALUE,'/gpx/trk','xmlns="http://www.topografix.com/GPX/1/1"'))) t1, 
       TABLE(XMLSequence(EXTRACT(VALUE(t1),'trk[number=' || EXTRACTVALUE(VALUE(t1), 'trk/number') || ']','xmlns="http://www.topografix.com/GPX/1/1"'))) allSegments;
  
TRACK_NUMBER TRACK_NAME GEOM
------------ ---------- ------------------------------------------------------------------------------------------------------------------------------------------------------------------------
1            07-SEP-04  MDSYS.SDO_GEOMETRY(3002,8307,null,MDSYS.SDO_ELEM_INFO_ARRAY(1,2,1),MDSYS.SDO_ORDINATE_ARRAY(121.056118,14.595809,49.645264,...,120.246134,15.043287,209.224121)) 
2            08-SEP-04  MDSYS.SDO_GEOMETRY(3002,8307,null,MDSYS.SDO_ELEM_INFO_ARRAY(1,2,1),MDSYS.SDO_ORDINATE_ARRAY(120.254095,15.043309,210.666016,...,120.236864,15.034811,114.053589)) 
3            08-SEP-04  MDSYS.SDO_GEOMETRY(3006,8307,null,MDSYS.SDO_ELEM_INFO_ARRAY(1,2,1,478,2,1),MDSYS.SDO_ORDINATE_ARRAY(120.254095,15.043309,210.666016,...,120.558879,14.908383,28.015503)) 
  
3 rows selected

So, a combination of SQL and PL/SQL solved the problem of how to generate MULTILINESTRINGS for tracks with multiple segments. Once I upgrade to 11gR1 I will re-look at this problem again to see if use of XPath’s COUNT function can help me implement a solution based on pure SQL.

Conclusion

XMLDB (or even any “horizontal market” XML processing tool) is an excellent tool for handling and processing GPX and other geospatial XML formats. The benefits for use of XMLDB include:

  • Fully integrated into the Oracle database;
  • A powerful, generic tool not limited to geospatial data processing;
  • No additional licensing cost;
  • No need for a separate application or application server;
  • Updates and processing can be executed by Oracle’s DBMS_JOB or DBMS_SCHEDULER queues.

I don’t profess to be an XML or XMLDB expert. If you find any errors in what I have written, please write to me and let me know and I will correct them.

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