Hi Carson, indeed it does. As mentioned in my previous mail, i've solved the problem by simply exporting the lines into a new projection (in this case: british national grid). Although it is possible doing it this way, i really would apreciate if there would be a much smarter behaviour for this in qGIS in the future ;) Thanks,Freddy
Frederick Löbig Röderichstraße 59 60489 Frankfurt am Main --- E:: frederick.loe...@grunsnid.de P: +49 (0) 69 - 78 99 52 41 M: +49 (0) 174 - 70 89 296 --- Office: euNetworks GmbH Ludwig-Landmann-Straße 40560486 Frankfurt am MainP: +49 (0) 69 - 90 554 - 532 E: frederick.loe...@eunetworks.com S: floebig This email and any attachments may contain confidential and/or legally privileged information. If you are not the intended recipient, please delete the email without reading it and notify the sender. > Date: Fri, 4 Mar 2011 18:49:32 +0000 > Subject: Re: [Qgis-user] Incorrect Results in Buffer > From: carson.far...@gmail.com > To: frederick.loe...@grunsnid.de > CC: frederick.loe...@live.de; qgis-user@lists.osgeo.org > > Hi Frederick, > > > The situation: I have my project SRS set to EPSG:900913 (web mercator). As a > > layer I have a line-layer also with EPSG:900913 as a projection. The > > project-wide units are meters. I now want to add a 250m buffer around the > > lines so i click vector->geoprocessing tools->Buffer(s), select my > > line-layer, type in 250 for 250 meters, check dissolve buffer results ans > > set a filename. Then the buffer is created, but unfortunately, when I export > > the buffer as kml and check the buffer width in Google Earth it is around > > 150-160 meters, so far off my 250meters. I also checked the distance with > > the qGIS measurement-tool - same result. > By 'same result' here, do you mean it measures 150-160 metres in QGIS as well? > > The lines are located in London. I have tried to use simple WGS84 and the > > british nationale grind, but none of them worked. > What does this mean? No output was created, or they produced similarly > 'wrong' results? > > This has to do something with differente base-ellipsoids I think, but I did > > not get to the bottom of the problem. > > Could anybody please help me with this? > Well one possible issue could be due to the fact that fTools (i.e. the > vector menu), does not take into account the project CRS _or_ 'on the > fly projection'. In fact, it only considers the CRS of the unput > layer. This being the case, if the units for your input layer aren't > in metres, then neither will your output. There are several reasons > for why fTools does this, though it's possible that this will be > changed in the future. > > Does that shed any light on the error? > > Carson > > -- > Carson J. Q. Farmer > ISSP Doctoral Fellow > National Centre for Geocomputation > National University of Ireland, Maynooth, > http://www.carsonfarmer.com/
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