[postgis-users] Computing the lenght of a building's edges looking on a direction

[Paolo Crosato]

Thank you very much! I'll try with this approach.

Regards,

Paolo

Il 17/06/2015 18:24, Rémi Cura ha scritto:
> Hm,
> quite easy normally (method proposed above won't work).
> First break your polygon into segment, for instance with
> https://github.com/Remi-C/PPPP_utilities/blob/master/postgis/rc_DumpSegments.sql
> Then, for each segment, compute the angle between first and last 
> point, using |ST_Azimuth, and st_pointN.
>
> |
> |Now, keep the segment where the abs(angle) is between pi/2
>  -tolerancy and pi/2+tolerancy
> ( you should add a tolerancy , nobody will be facing exactly north)*.
> *|
> |*Now simply sum the st_length of found segments.
>
> *|
> |*Cheers,
> *|
> |*Rémi-C
> *|
>
> 2015-06-17 17:40 GMT+02:00 Komяpa <me at komzpa.net <mailto:me at komzpa.net>>:
>
>     Hello,
>
>     you can apply ST_ForceRHR, break your polygons into segments and
>     sum length of the ones that go from right to left, that is, where
>     ST_X(ST_StartPoint(geom)) < ST_X(ST_StartPoint(geom)).
>
>     That's basically visibility problem, been there somewhere around
>     https://github.com/Komzpa/Mapnik-Sheets/blob/master/3d-buildings/3dbuil.xml#L95
>
>     2015-06-17 18:12 GMT+03:00 Paolo Crosato
>     <paolo.crosato at targaubiest.com
>     <mailto:paolo.crosato at targaubiest.com>>:
>
>         Hi,
>
>         I have a set of 2d polygons representing buildings. For each
>         one, I have to find the lenght of the edges that look towards
>         north.
>
>         Here http://imgur.com/HgpO2yH there is a small picture with a
>         test case, I have to compute the lenght of the red edges.
>
>         Has anybody any suggestion on how to do this in postgis?
>
>         Thanks for any input,
>
>         Regards
>
>         -- 
>         Paolo Crosato
>         Software engineer/Custom Solutions
>         e-mail: paolo.crosato at targaubiest.com
>         <mailto:paolo.crosato at targaubiest.com>
>
>         _______________________________________________
>         postgis-users mailing list
>         postgis-users at lists.osgeo.org
>         <mailto:postgis-users at lists.osgeo.org>
>         http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users
>
>
>
>
>     -- 
>     Darafei "Komяpa" Praliaskouski
>     OSM BY Team - http://openstreetmap.by/
>     xmpp:me at komzpa.net <mailto:xmpp%3Ame at komzpa.net>
>     mailto:me at komzpa.net <mailto:me at komzpa.net>
>
>     _______________________________________________
>     postgis-users mailing list
>     postgis-users at lists.osgeo.org <mailto:postgis-users at lists.osgeo.org>
>     http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users
>
>
>
>
> _______________________________________________
> postgis-users mailing list
> postgis-users at lists.osgeo.org
> http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users


-- 
Paolo Crosato
Software engineer/Custom Solutions

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/postgis-users/attachments/20150618/dcf68cf7/attachment.html>