<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto">Hi,<div><br><div>If you’re comfortable with python you can always follow the introduction here.</div><div><br></div><div><a href="https://pcjericks.github.io/py-gdalogr-cookbook/raster_layers.html#polygonize-a-raster-band">https://pcjericks.github.io/py-gdalogr-cookbook/raster_layers.html#polygonize-a-raster-band</a></div><div><br></div><div>You can also send me a link to the file and I could try on a windows box. You could check bug reports to see if it’s been reported also.<br><br><div dir="ltr">Nicolas Cadieux<div><a href="https://gitlab.com/njacadieux">https://gitlab.com/njacadieux</a></div></div><div dir="ltr"><br><blockquote type="cite">Le 29 mars 2022 à 21:04, Shinoto, PD Dr. Maria <maria.shinoto@zaw.uni-heidelberg.de> a écrit :<br><br></blockquote></div><blockquote type="cite"><div dir="ltr"><span>Nicolas, </span><br><span></span><br><span>Tried it once again, short names and reasonable paths do not work. I am on Mac, QGIS 3.24, will test some reasons for the failure tomorrow again and report. Thanks for your advice, </span><br><span></span><br><span>Maria</span><br><span></span><br><span></span><br><span></span><br><blockquote type="cite"><span>Am 30.03.2022 um 09:34 schrieb Nicolas Cadieux via Qgis-user <qgis-user@lists.osgeo.org>:</span><br></blockquote><blockquote type="cite"><span></span><br></blockquote><blockquote type="cite"><span>Hi,</span><br></blockquote><blockquote type="cite"><span></span><br></blockquote><blockquote type="cite"><span>"Polygonize" should work well to vectorize the raster classes. If you have problems with the file name, try simplifying the file name to the bare minimun like c:\temp\toto.shp if you're on Windows. Make sure you have no spaces or accents in the path (this includes the user path of your operation system). Notice that there are two polygonize algorithm. One is from QGIS and one is from GDAL. Try both. They are probably both based on GDAL but one (probably the QGIS one) may have an easier time with accents, spaces or special characters like '\n'.</span><br></blockquote><blockquote type="cite"><span></span><br></blockquote><blockquote type="cite"><span>Good luck</span><br></blockquote><blockquote type="cite"><span></span><br></blockquote><blockquote type="cite"><span>Nicolas</span><br></blockquote><blockquote type="cite"><span></span><br></blockquote><blockquote type="cite"><span>On 2022-03-29 7:51 p.m., Shinoto, PD Dr. Maria via Qgis-user wrote:</span><br></blockquote><blockquote type="cite"><blockquote type="cite"><span>Hi Kirk,</span><br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><span></span><br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><span>that was helpful, thank you.</span><br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><span></span><br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><span>I am not yet where I need to be, but so far I could create two classes with the formula found in the docs (https://docs.qgis.org/3.10/en/docs/user_manual/working_with_raster/raster_analysis.html) along this line:</span><br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><span></span><br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><span> `("slope@1" < 50) * 1 + ("slope@1" >= 50) * 2`</span><br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><span></span><br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><span>At this moment, my biggest problem is creating the vector file, the window claims that the file name is too long. This cannot be the case, and the directory itself should be OK. So now I am trying to get this done, and then I will test three classes, which I did not get working up to now either.</span><br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><span></span><br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><span>If there are easy answers to these two questions, I would be pleased, otherwise, I will try tomorrow.</span><br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><span></span><br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><span>Thanks a lot,</span><br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><span>Maria</span><br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><span></span><br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><span></span><br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><span></span><br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><span>Am 30.03.2022 um 07:14 schrieb kirk <kirk@nortekresources.com>:</span><br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><span></span><br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><span>Hi Maria.</span><br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><span>The symbology does not reclassify the underlying raster, it just changes the way it is displayed. Use the raster calculator to generate a new raster with the Classes you require. The native qgis calculator works well. You can find it in the upper word menu under raster. Once you have your raster reclassified, you can then convert it to a vector format</span><br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><span></span><br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><span>Kirk Schmidt</span><br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><span></span><br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><span></span><br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><span></span><br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><span>Sent from my Galaxy</span><br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><span></span><br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><span></span><br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><span>-------- Original message --------</span><br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><span>From: "Shinoto, PD Dr. Maria via Qgis-user" <qgis-user@lists.osgeo.org></span><br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><span>Date: 2022-03-29 6:32 p.m. (GMT-04:00)</span><br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><span>To: qgis forum <qgis-user@lists.osgeo.org></span><br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><span>Subject: [Qgis-user] creating vector layer from slope map with few classes</span><br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><span></span><br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><span>Hi,</span><br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><span></span><br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><span>I have created a slope map from a DTM.</span><br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><span></span><br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><span>I have limited the symbology to three meaningful classes and wish to create a vector layer with polygons of three classes from that. The conditions are One-Channel-Pseudocolor, Channel1 (Gray), interpolation discrete, modus "fortlaufend" -- not identical interval or quantile, 3 classes with values <=20, 20 - 40, > 40.</span><br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><span></span><br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><span>The classes show up in the layer design panel symbology tab, but the layer browser still (thankfully!) shows the greyscale ramp.</span><br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><span></span><br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><span>I wish to create a vector layer with polygons from the 3 classes.</span><br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><span></span><br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><span>All solutions I have looked up work under slightly different condition. After all I do not know how to get the data of the DTM into three classes like "Flat-Gentle-Steep"; I think the vectorization should work easily then.</span><br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><span></span><br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><span>Can anybody hint me to a solution?</span><br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><span></span><br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><span></span><br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><span>Thanks and best wishes,</span><br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><span>Maria</span><br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><span>_______________________________________________</span><br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><span>Qgis-user mailing list</span><br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><span>Qgis-user@lists.osgeo.org</span><br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><span>List info: https://lists.osgeo.org/mailman/listinfo/qgis-user</span><br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><span>Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user</span><br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><blockquote type="cite"><span></span><br></blockquote></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><span>_______________________________________________</span><br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><span>Qgis-user mailing list</span><br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><span>Qgis-user@lists.osgeo.org</span><br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><span>List info: https://lists.osgeo.org/mailman/listinfo/qgis-user</span><br></blockquote></blockquote><blockquote type="cite"><blockquote type="cite"><span>Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user</span><br></blockquote></blockquote><blockquote type="cite"><span></span><br></blockquote><blockquote type="cite"><span>-- </span><br></blockquote><blockquote type="cite"><span>Nicolas Cadieux</span><br></blockquote><blockquote type="cite"><span>https://gitlab.com/njacadieux</span><br></blockquote><blockquote type="cite"><span></span><br></blockquote><blockquote type="cite"><span>_______________________________________________</span><br></blockquote><blockquote type="cite"><span>Qgis-user mailing list</span><br></blockquote><blockquote type="cite"><span>Qgis-user@lists.osgeo.org</span><br></blockquote><blockquote type="cite"><span>List info: https://lists.osgeo.org/mailman/listinfo/qgis-user</span><br></blockquote><blockquote type="cite"><span>Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user</span><br></blockquote><span></span><br></div></blockquote></div></div></body></html>