[postgis-users] Clarification on PostGIS/JTS?

[Paul Ramsey]

OK, in the style of assertions-in-point-form:

- PostGIS as it stands lacks binary predicates (Relate(), Touches(), 
Contains(), Inside(), Disjoint(), etc) and spatial operators (Buffer(), 
Intersection(), Union(), etc).
- JTS (the Java Topology Suite, 
http://www.vividsolutions.com/jts/jtshome.htm) is an open source library 
which implements all of the above functions, but in Java. PostGIS needs 
a C or C++ library in order to take advantage of the JTS algorithms.
- Refractions Research (http://www.refractions.net) and Vivid Solutions 
(http://www.vividsolutions.com) have taken it onto themselves to fund a 
graduate student at the University of Victoria to port the JTS 
algorithms from Java to C++.
- The result of this Java to C++ porting project will be C++ library 
named GEOS (Geometry Engine, Open Source). The project site is at 
http://geos.refractions.net
- The graduate student (Yury Bychkov) has been working for about 3 
months, and has completed the GEOS object framework, and the binary 
predicates.
- The GEOS binary predicates have been tested against the JTS test 
harness and have passed all the JTS test cases (which include degenerate 
cases capable of mortally confusing ArdSDE).
- Dave Blasby has recently completed an integration of GEOS into the 
PostGIS framework, and has run all the JTS test cases inside of PostGIS, 
  with a 100% success rate. There are some changes to be made in object 
instantiation and in the make files and then the changes will be 
committed to CVS.
- At that point, PostGIS will support all the binary predicate 
operators, if you have the GEOS library installed.  In much the same 
way, PostGIS supports coordinate transformation if you have Proj4 installed.
- There are still some performance and coding style improvements to be 
made to the binary predicates which will probably keep Yury occupied 
until Christmas. After that he will start on the spatial operators, 
which are somewhat harder.
- Having done the GEOS integration, Dave will be able to add support to 
further GEOS functionality (like the spatial operators) very very easily 
as Yury completes them. With luck we should have all the operators 
completed before the end of the funded project in the summer of 2003.
- The next formal release of PostGIS will be version 0.8.0 and will 
include the binary predicate support. It will occur before Christmas. 
CVS access to these capabilities should be available within a couple weeks.

Paul

C F wrote:
> Instead of asking the millions of 
> questions I have, maybe I could just prod someone to write a 
> comprehensive message about the near-future of PostGIS....

-- 
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      /
      | Paul Ramsey
      | Refractions Research
      | Email: pramsey at refractions.net
      | Phone: (250) 885-0632
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