Re: [JPP-Devel] new OffsetCurve plugin for OpenJUMP

[Michaël Michaud]

Hi   One quick question: PostGIS and Spatialite ST_OffsetCurve function is turning the line direction with right hand offset ST_OffsetCurve(GEOMETRY,15,0) Just read PostGIS documentation today (I'd better have read it before, but better late than never ;-)   This is not always a good behavior. User is perhaps willing to create parallel pipelines or roads and maintain the original line direction both with  the left and right side offsets. How does your plugin work by default with right side offset? If it is also turning the direction, how about having an option “maintain line direction”? What is good in PostGIS behaviour is that it is consistent. Not sure I can assume anything about line orientation with my plugin. But you're right, orientation is an important point. IMHO, having the same orientation as the source or the opposite one is not so important as it is easy to reverse lines, (but it will be easy to add an option if you have a use case, easier than making final orientation consistent with the initial orientation). Also, it would be good to compare postgis results and oj results for every non-trivial case. Thanks for your valuable input, Michaël   -Jukka Rahkonen-   Michaël Michaud wrote:   Hi all, Just added this plugin (should be available in next NB). Firstly, I thought it was available in JTS, but the JTS OffsetCurveBuilder produce a rough offset curve often containing self-intersection and needs to be post-processed to get something more usable. Here is the process : - compute rough offset curve (distance=d) - node the result (with UnaryUnionOp) - remove components located at a distance < d from the source   (this is the tricky part as the computed offset curve itself may    be slightly inside the distance - I estimated the error and took    1 more percent to be sur no valid component are discarded,    but it may still fails in some situations like using join mitre    with a small limit or using a fixed precision model) - merge the remaining linestrings Here are some results   ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Jump-pilot-devel mailing list Jump-pilot-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/jump-pilot-devel

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Live Security Virtual Conference
Exclusive live event will cover all the ways today's security and 
threat landscape has changed and how IT managers can respond. Discussions 
will include endpoint security, mobile security and the latest in malware 
threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/
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