Yes.. as far as i know JTS has no optimization, but.. * I implemented in the mapgen toolbox an union based on attributes that utilizes the jts quadtree. * recently Michael improved the JUMP deliverd union to speed up (can't remember how) and added as well an option for unioning only when attributes are similar.
it may be an option to call Michaels optimized code for the post-unioning in the buffer method stefan Larry Becker schrieb: > Hi Martin, > > The union operation is implemented by buffering the union of the > input, rather than the union of the input buffered, if you see the > distinction. I was hoping JTS had already optimized this, but from > what you are saying, I would guess not. > > Larry > > On 8/31/07, Martin Davis <[EMAIL PROTECTED]> wrote: >> Cool... >> >> I think that one way around the "slow union" problem is to develop a >> "Cascading Union" function. This will build up a union of multiple >> geometries by forming them into a tree, and recursively unioning the >> branches of the tree from the leaves to the root. In theory this >> should provide a fairly optimal balance between performance and memory use. >> >> A nice way to form the tree would be to add the input geometries to a >> JTS Quadtree or STRtree and then traverse the tree in depth-first >> order. Unfortunately currently the implementations don't support the >> ability to traverse the tree in any order - this wouldn't be too hard to >> add, though. >> >> Thoughts? Anyone keen on trying this out? >> >> Martin >> >> >> >> Larry Becker wrote: >>> I have committed the improved buffer plugin. Three sample screens are >>> attached in english, french, and german. It now supports buffering >>> the selection. It provides a convenience union option. The sidebar >>> picture now previews the current options. It copies attributes by >>> default, even from selections on multiple layers, but this can be >>> turned off. It supports setting the number of segments in a quarter >>> circle. >>> >>> Be careful with the union operation. With large selections, it can >>> take a long time. For instance using Uwe's GeoCity project, I tried >>> to buffer everything by 1000 meters. Without union it completed in >>> about 20 seconds, and with union I finally killed it after 5 minutes. >>> >>> regards, >>> Larry Becker >>> >>> >>> ------------------------------------------------------------------------ >>> >>> >>> ------------------------------------------------------------------------ >>> >>> >>> ------------------------------------------------------------------------ >>> >>> ------------------------------------------------------------------------ >>> >>> ------------------------------------------------------------------------- >>> This SF.net email is sponsored by: Splunk Inc. >>> Still grepping through log files to find problems? Stop. >>> Now Search log events and configuration files using AJAX and a browser. >>> Download your FREE copy of Splunk now >> http://get.splunk.com/ >>> ------------------------------------------------------------------------ >>> >>> _______________________________________________ >>> Jump-pilot-devel mailing list >>> Jump-pilot-devel@lists.sourceforge.net >>> https://lists.sourceforge.net/lists/listinfo/jump-pilot-devel >>> >> -- >> Martin Davis >> Senior Technical Architect >> Refractions Research, Inc. >> (250) 383-3022 >> >> >> ------------------------------------------------------------------------- >> This SF.net email is sponsored by: Splunk Inc. >> Still grepping through log files to find problems? Stop. >> Now Search log events and configuration files using AJAX and a browser. >> Download your FREE copy of Splunk now >> http://get.splunk.com/ >> _______________________________________________ >> Jump-pilot-devel mailing list >> Jump-pilot-devel@lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/jump-pilot-devel >> > > ------------------------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/ _______________________________________________ Jump-pilot-devel mailing list Jump-pilot-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/jump-pilot-devel
