Do you have to maintain the data in vector? Grass has a viewshed tool for raster inputs, which I believe ships with QGIS.
http://grass.itc.it/grass62/manuals/html62_user/r.los.html -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of diplonics Sent: 14 May 2009 19:10 To: [email protected] Subject: [postgis-users] Viewshed Isovist Hi All, Just wondering if this can be done in PostGIS and if not does anyone know of the simplest method to get it done. I have 2 PostGIS polygon geometry tables and I want to basically do is an isovist/viewshed/line of sigth operation. I know an intersection operation can isolate where the polys are spatially equal but what I want is some sort of set complement operation where it will also remove all polygon sections without direct line of sight. Image 1 is a sample of my two data sets. The purple polys are building outlines while the yellow poly is an unobstructed viewshed from a line. http://www.nabble.com/file/p23546020/ViewShed01.png Image 2 is a sample of the desired result. Using a PostGIS intersection operation I can isolate the green sections, but I want to return a geometry that is the yellow section with the green and red sections removed. http://www.nabble.com/file/p23546020/ViewShed02.png Any advice on this problem, or links to help, would be greatly appreciated. Thanks -- View this message in context: http://www.nabble.com/Viewshed-Isovist-tp23546020p23546020.html Sent from the PostGIS - User mailing list archive at Nabble.com. _______________________________________________ postgis-users mailing list [email protected] http://postgis.refractions.net/mailman/listinfo/postgis-users This e-mail message and any attached file is the property of the sender and is sent in confidence to the addressee only. The contents are not to be disclosed to anyone other than the addressee. Unauthorised recipients are requested to preserve this confidentiality and to advise the sender immediately of any error in transmission. If you experience difficulty with opening any attachments to this message, or with sending a reply by email, please telephone on + 44-(0)1235 438151 or fax on + 44-(0)1235 438188. Any advice contained in this e-mail or any accompanying file attached hereto is for information purposes only. RPS do not take any responsibility for differences between the original and the transmission copy or any amendments made thereafter. If the addressee requires RPS to be responsible for the contents of this e-mail, RPS will be pleased to issue a signed hard copy of the document upon request. RPS Planning and Development Limited, company number: 02947164 (England). Registered office: Centurion Court, 85 Milton Park Abingdon Oxfordshire OX14 4RY. RPS Group Plc web link: <http://www.rpsgroup.com> _______________________________________________ postgis-users mailing list [email protected] http://postgis.refractions.net/mailman/listinfo/postgis-users
