You can use the method that I outline here: http://woostuff.wordpress.com/2011/02/23/total-length-of-selected-objects-qgis-via-python/
- Nathan On Wed, Jun 20, 2012 at 8:14 PM, Zoltan Szecsei <[email protected]> wrote: > Hi, > I've opened a DGN file of contours, and would like to calculate the sum of > the lengths of all the contours. > > Using Vector->Analysis Tools->Sum Line Lengths is totally counter intuitive > (OK, for me!). > > Why do I have to have a polygon in order to sum line lengths - In SHAPE file > methodology those geometries are even in separate files! > And then to create a new poly layer in order to see the calculated value > seems kind of arb. > Is the polygon perimeter also added to the calculated length? > > If said polygon is purely for creating a selection subset of the > line-lengths to be summed, then why not use the selection tool instead? > > When querying an individual line, its length is shown as a derived field. If > there was a way to put derived fields into the attribute tables, then at > least that column could be summed. > > Anyway, it seems like I have missed the point of summing line lengths in > this way, so please can someone enlighten me why this methodology is useful. > > Thanks & regards, > Zoltan > > > -- > > =========================================== > Zoltan Szecsei PrGISc [PGP0031] > Geograph (Pty) Ltd. > P.O. Box 7, Muizenberg 7950, South Africa. > > 65 Main Road, Muizenberg 7945 > Western Cape, South Africa. > > 34° 6'16.35"S 18°28'5.62"E > > Tel: +27-21-7884897 Mobile: +27-83-6004028 > Fax: +27-86-6115323 www.geograph.co.za > =========================================== > > _______________________________________________ > Qgis-user mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/qgis-user _______________________________________________ Qgis-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/qgis-user
