GeoTools

Extract the authority code from an unidentified CRS

Details

  • Type: Improvement Improvement
  • Status: Closed Closed
  • Priority: Major Major
  • Resolution: Fixed
  • Affects Version/s: 2.3.0, 2.4.0
  • Fix Version/s: 2.4-M3
  • Component/s: referencing
  • Labels:
    None

Description

There is a demand for a way to get the EPSG authority code for an unidentified CRS. "Unidentified" means a CRS without identifiers. In Well Known Text (WKT) terms, this means a CRS without AUTHORITY[...] element.

One possible approach is to scan over the full EPSG database, instantiate every CRS and compare them with the unidentified CRS until a match is found. The comparaison is done with CRS.equalsIgnoreMetadata(...). However this approach is slow and consume a lot of resources. For some factory like the SQL-backed EPSG factory, it is possible to reduce the set of CRS to instantiate.

This request for enhancement is about defining an API for CRS lookup which provides a opportunity for optimisation in some authority factories like the EPSG one.

Issue Links

duplicates

Sub-task - The sub-task of the issue GEOT-511 Determine Authority code from CRS

  • Minor - Minor loss of function, or other problem where easy workaround is present.
  • Closed - The issue is considered finished, the resolution is correct. Issues which are not closed can be reopened.

Activity

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Martin Desruisseaux added a comment -
Andrea commited a first version in the CRS class as of revision 24275. This code has been partially refactored as of revision 24384 with a few optimisations in EPSG FactoryUsingSQL factory case. A simple test suggests that this implementation is 4 times faster than a full scan over the full EPSG database. It would probably be possible to do better than that, if we happen to have more time to spend on this work.

There is some remaining work to do in AllAuthorityFactory before we can use the new API in CRS.lookupIdentifier.
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Martin Desruisseaux added a comment - Andrea commited a first version in the CRS class as of revision 24275. This code has been partially refactored as of revision 24384 with a few optimisations in EPSG FactoryUsingSQL factory case. A simple test suggests that this implementation is 4 times faster than a full scan over the full EPSG database. It would probably be possible to do better than that, if we happen to have more time to spend on this work. There is some remaining work to do in AllAuthorityFactory before we can use the new API in CRS.lookupIdentifier.
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Martin Desruisseaux added a comment -
First working version commited on trunk as of revision 25397. A new method has been added in the CRS utilities class:

    String lookupIdentifier(IdentifiedObject object, boolean fullScan);

The previous method has been deprecated (its implementation has been left unchanged in order to avoid breaking existing code, since the "lookupIdentifier" implementation is non-trivial):

    @Deprecated
    String lookupIdentifier(IdentifiedObject object, Set authorities, boolean fullScan);

Note: if a user wants to scan only over some specific authorities (like what the old method allows), he can do that by using the new IdentifiedObjectFinder class explicitly. The new CRS.lookupIdentifier(...) method is just a convenience wrapper for making use of this new class.

The new method should be faster in two ways:

   * Use some SQL queries in order to get a smaller set of CRS candidates to instantiate from the EPSG database, instead of trying all CRS returned by AuthorityFactory.getAuthorityCodes().

   * Avoid some duplicated CRS instantiations. For example (x,y) and (y,x) axis order are tried in the same pass over EPSG code candidates, instead of making one pass for (x,y) and a second pass for (y,x) with CRS instantiations on each pass.

Waiting confirmation that the new method work as expected before to close this RFE.
Show
Martin Desruisseaux added a comment - First working version commited on trunk as of revision 25397. A new method has been added in the CRS utilities class:     String lookupIdentifier(IdentifiedObject object, boolean fullScan); The previous method has been deprecated (its implementation has been left unchanged in order to avoid breaking existing code, since the "lookupIdentifier" implementation is non-trivial):     @Deprecated     String lookupIdentifier(IdentifiedObject object, Set authorities, boolean fullScan); Note: if a user wants to scan only over some specific authorities (like what the old method allows), he can do that by using the new IdentifiedObjectFinder class explicitly. The new CRS.lookupIdentifier(...) method is just a convenience wrapper for making use of this new class. The new method should be faster in two ways:    * Use some SQL queries in order to get a smaller set of CRS candidates to instantiate from the EPSG database, instead of trying all CRS returned by AuthorityFactory.getAuthorityCodes().    * Avoid some duplicated CRS instantiations. For example (x,y) and (y,x) axis order are tried in the same pass over EPSG code candidates, instead of making one pass for (x,y) and a second pass for (y,x) with CRS instantiations on each pass. Waiting confirmation that the new method work as expected before to close this RFE.
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Andrea Aime added a comment -
I've tried this and when it works, it's fast. Yet I found some CRS with a strange behaviour, and when I tried to investigate I was welcomed by a very nasty exception.

Basically , the following little program:

public static void main(String[] args) throws NoSuchAuthorityCodeException, FactoryException {
        System.out.println(CRS.decode("EPSG:4326"));
}

dropped directly in the espg-hsql test directory (so classpath is fine) throws the following exception.

org.opengis.referencing.NoSuchAuthorityCodeException: Authority "EPSG" is unknown or doesn't match the supplied hints. Maybe it is defined in an unreachable JAR file?
at org.geotools.referencing.factory.ManyAuthoritiesFactory.noSuchAuthority(ManyAuthoritiesFactory.java:545)
at org.geotools.referencing.factory.ManyAuthoritiesFactory.getAuthorityFactory(ManyAuthoritiesFactory.java:523)
at org.geotools.referencing.factory.ManyAuthoritiesFactory.getCRSAuthorityFactory(ManyAuthoritiesFactory.java:606)
at org.geotools.referencing.factory.AuthorityFactoryAdapter.createCoordinateReferenceSystem(AuthorityFactoryAdapter.java:657)
at org.geotools.referencing.factory.BufferedAuthorityFactory.createCoordinateReferenceSystem(BufferedAuthorityFactory.java:685)
at org.geotools.referencing.CRS.decode(CRS.java:362)
at org.geotools.referencing.CRS.decode(CRS.java:297)
at org.vfny.geoserver.jetty.CRSTest.main(CRSTest.java:16)
Caused by: org.geotools.factory.FactoryNotFoundException: No factory of kind "CRSAuthorityFactory" found.
at org.geotools.factory.FactoryRegistry.getServiceProvider(FactoryRegistry.java:354)
at org.geotools.factory.FactoryCreator.getServiceProvider(FactoryCreator.java:115)
at org.geotools.referencing.ReferencingFactoryFinder.getAuthorityFactory(ReferencingFactoryFinder.java:239)
at org.geotools.referencing.ReferencingFactoryFinder.getCRSAuthorityFactory(ReferencingFactoryFinder.java:449)
at org.geotools.referencing.factory.AllAuthoritiesFactory.fromFactoryRegistry(AllAuthoritiesFactory.java:136)
at org.geotools.referencing.factory.ManyAuthoritiesFactory.getAuthorityFactory(ManyAuthoritiesFactory.java:507)
... 6 more
Exception in thread "main"

I also tried on the command line from withing the binaries directory:

ava -Dorg.geotools.referencing.forceXY=true -classpath gt2-epsg-hsql-2.4-SNAPSHOT.jar org.geotools.referencing.CRS "EPSG:4326"
Authority "EPSG" is unknown or doesn't match the supplied hints. Maybe it is defined in an unreachable JAR file?

Whilst the following works:

C:\progetti\geotools\trunk\target\binaries>java -Dorg.geotools.referencing.forceXY=true -classpath gt2-epsg-hsql-2.4-SNAPSHOT.jar org.geotools.referencing.CRS -authority=EPSG 4326
GEOGCS["WGS 84",
  DATUM["World Geodetic System 1984",
    SPHEROID["WGS 84", 6378137.0, 298.257223563, AUTHORITY["EPSG","7030"]],
    AUTHORITY["EPSG","6326"]],
  PRIMEM["Greenwich", 0.0, AUTHORITY["EPSG","8901"]],
  UNIT["degree", 0.017453292519943295],
  AXIS["Geodetic latitude", NORTH],
  AXIS["Geodetic longitude", EAST],
  AUTHORITY["EPSG","4326"]]

What puzzles me is that org.geotools.referencing.CRSTest does work and it exercises CRS.decode... but I can't see the difference (it works both in mvn install and in my Eclipse environment).
Show
Andrea Aime added a comment - I've tried this and when it works, it's fast. Yet I found some CRS with a strange behaviour, and when I tried to investigate I was welcomed by a very nasty exception. Basically , the following little program: public static void main(String[] args) throws NoSuchAuthorityCodeException, FactoryException {         System.out.println(CRS.decode("EPSG:4326")); } dropped directly in the espg-hsql test directory (so classpath is fine) throws the following exception. org.opengis.referencing.NoSuchAuthorityCodeException: Authority "EPSG" is unknown or doesn't match the supplied hints. Maybe it is defined in an unreachable JAR file? at org.geotools.referencing.factory.ManyAuthoritiesFactory.noSuchAuthority(ManyAuthoritiesFactory.java:545) at org.geotools.referencing.factory.ManyAuthoritiesFactory.getAuthorityFactory(ManyAuthoritiesFactory.java:523) at org.geotools.referencing.factory.ManyAuthoritiesFactory.getCRSAuthorityFactory(ManyAuthoritiesFactory.java:606) at org.geotools.referencing.factory.AuthorityFactoryAdapter.createCoordinateReferenceSystem(AuthorityFactoryAdapter.java:657) at org.geotools.referencing.factory.BufferedAuthorityFactory.createCoordinateReferenceSystem(BufferedAuthorityFactory.java:685) at org.geotools.referencing.CRS.decode(CRS.java:362) at org.geotools.referencing.CRS.decode(CRS.java:297) at org.vfny.geoserver.jetty.CRSTest.main(CRSTest.java:16) Caused by: org.geotools.factory.FactoryNotFoundException: No factory of kind "CRSAuthorityFactory" found. at org.geotools.factory.FactoryRegistry.getServiceProvider(FactoryRegistry.java:354) at org.geotools.factory.FactoryCreator.getServiceProvider(FactoryCreator.java:115) at org.geotools.referencing.ReferencingFactoryFinder.getAuthorityFactory(ReferencingFactoryFinder.java:239) at org.geotools.referencing.ReferencingFactoryFinder.getCRSAuthorityFactory(ReferencingFactoryFinder.java:449) at org.geotools.referencing.factory.AllAuthoritiesFactory.fromFactoryRegistry(AllAuthoritiesFactory.java:136) at org.geotools.referencing.factory.ManyAuthoritiesFactory.getAuthorityFactory(ManyAuthoritiesFactory.java:507) ... 6 more Exception in thread "main" I also tried on the command line from withing the binaries directory: ava -Dorg.geotools.referencing.forceXY=true -classpath gt2-epsg-hsql-2.4-SNAPSHOT.jar org.geotools.referencing.CRS "EPSG:4326" Authority "EPSG" is unknown or doesn't match the supplied hints. Maybe it is defined in an unreachable JAR file? Whilst the following works: C:\progetti\geotools\trunk\target\binaries>java -Dorg.geotools.referencing.forceXY=true -classpath gt2-epsg-hsql-2.4-SNAPSHOT.jar org.geotools.referencing.CRS -authority=EPSG 4326 GEOGCS["WGS 84",   DATUM["World Geodetic System 1984",     SPHEROID["WGS 84", 6378137.0, 298.257223563, AUTHORITY["EPSG","7030"]],     AUTHORITY["EPSG","6326"]],   PRIMEM["Greenwich", 0.0, AUTHORITY["EPSG","8901"]],   UNIT["degree", 0.017453292519943295],   AXIS["Geodetic latitude", NORTH],   AXIS["Geodetic longitude", EAST],   AUTHORITY["EPSG","4326"]] What puzzles me is that org.geotools.referencing.CRSTest does work and it exercises CRS.decode... but I can't see the difference (it works both in mvn install and in my Eclipse environment).
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Andrea Aime added a comment -
Oh, I've found what's wrong. In my launch configuration I had set -Dorg.geotools.referencing.forceXY=true.
Removing it makes the program work!
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Andrea Aime added a comment - Oh, I've found what's wrong. In my launch configuration I had set -Dorg.geotools.referencing.forceXY=true. Removing it makes the program work!
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Andrea Aime added a comment -
And the same goes for the command line version, removing axis forcing makes the decode work
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Andrea Aime added a comment - And the same goes for the command line version, removing axis forcing makes the decode work
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Martin Desruisseaux added a comment -
If CRS.decode("EPSG:4326") fails with -Dorg.geotools.referencing.forceXY=true, then we have a bug that need to be fixed...
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Martin Desruisseaux added a comment - If CRS.decode("EPSG:4326") fails with -Dorg.geotools.referencing.forceXY=true, then we have a bug that need to be fixed...
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Martin Desruisseaux added a comment -
Created GEOT-1263 for the "-Dorg.geotools.referencing.forceXY=true" issue.
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Martin Desruisseaux added a comment - Created GEOT-1263 for the "-Dorg.geotools.referencing.forceXY=true" issue.
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Andrea Aime added a comment -
Mass closing all issues that have been in "resolved" state for 2 months or more without any feedback or update
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Andrea Aime added a comment - Mass closing all issues that have been in "resolved" state for 2 months or more without any feedback or update

People

  • Assignee:
    Martin Desruisseaux
    Reporter:
    Martin Desruisseaux
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Dates

  • Created:
    Updated:
    Resolved: