Hi, If you’re comfortable with python you can always follow the introduction here.
https://pcjericks.github.io/py-gdalogr-cookbook/raster_layers.html#polygonize-a-raster-band 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. Nicolas Cadieux https://gitlab.com/njacadieux > Le 29 mars 2022 à 21:04, Shinoto, PD Dr. Maria > <[email protected]> a écrit : > > Nicolas, > > 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, > > Maria > > > >> Am 30.03.2022 um 09:34 schrieb Nicolas Cadieux via Qgis-user >> <[email protected]>: >> >> Hi, >> >> "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'. >> >> Good luck >> >> Nicolas >> >>> On 2022-03-29 7:51 p.m., Shinoto, PD Dr. Maria via Qgis-user wrote: >>> Hi Kirk, >>> >>> that was helpful, thank you. >>> >>> 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: >>> >>> `("slope@1" < 50) * 1 + ("slope@1" >= 50) * 2` >>> >>> 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. >>> >>> If there are easy answers to these two questions, I would be pleased, >>> otherwise, I will try tomorrow. >>> >>> Thanks a lot, >>> Maria >>> >>> >>> >>>> Am 30.03.2022 um 07:14 schrieb kirk <[email protected]>: >>>> >>>> Hi Maria. >>>> 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 >>>> >>>> Kirk Schmidt >>>> >>>> >>>> >>>> Sent from my Galaxy >>>> >>>> >>>> -------- Original message -------- >>>> From: "Shinoto, PD Dr. Maria via Qgis-user" <[email protected]> >>>> Date: 2022-03-29 6:32 p.m. (GMT-04:00) >>>> To: qgis forum <[email protected]> >>>> Subject: [Qgis-user] creating vector layer from slope map with few classes >>>> >>>> Hi, >>>> >>>> I have created a slope map from a DTM. >>>> >>>> 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. >>>> >>>> The classes show up in the layer design panel symbology tab, but the layer >>>> browser still (thankfully!) shows the greyscale ramp. >>>> >>>> I wish to create a vector layer with polygons from the 3 classes. >>>> >>>> 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. >>>> >>>> Can anybody hint me to a solution? >>>> >>>> >>>> Thanks and best wishes, >>>> Maria >>>> _______________________________________________ >>>> Qgis-user mailing list >>>> [email protected] >>>> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user >>>> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user >>>> >>> _______________________________________________ >>> Qgis-user mailing list >>> [email protected] >>> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user >>> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user >> >> -- >> Nicolas Cadieux >> https://gitlab.com/njacadieux >> >> _______________________________________________ >> Qgis-user mailing list >> [email protected] >> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user >> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user >
_______________________________________________ Qgis-user mailing list [email protected] List info: https://lists.osgeo.org/mailman/listinfo/qgis-user Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
