Hi Richard, this was great, a big thanks to you as well. Classifying was the first problem, and thanks to your step by step explanation, it worked well, easy, quick, producing exactly the results I wished for.
Cheers to you and the community, Maria > Am 30.03.2022 um 20:36 schrieb Richard McDonnell <[email protected]>: > > Hi Maria, > There is an option to reclassify a raster called Reclassify by Table, which > should create the classified raster you are looking for. > > You can find the Reclassify by Table in the Processing Toolbox, you can then > do the following. > 1. Select the Raster you want > 2. Under Reclassification table click on the button with the three dots. > a. You need to add a row for each class you want, by clicking Add Row > b. For each row set the Minimum and Maximum pixel Values and the new > Value > c. Click OK once you are happy > 3. Set your output no data value, in your case it can be zero > 4. Set Range boundaries as you require > 5. Set your Output data type, I would, based on your description select > Byte > 6. Set location to which you want to save your Raster. > > To polygonise the data then is just a simple matter of using the QGIS > Polygonize tool, which again can be accessed from the Processing Toolbar. Its > default settings should create the output you are looking for. > Hope the above goes some way to helping you. > > Regards, > > Richard > > > > —— > Richard McDonnell MSc GIS, FME Certified Professional > FRM Data Management > > —— > Oifig na nOibreacha Poiblí > Office of Public Works > > Sráid Jonathan Swift, Baile Átha Troim, Co na Mí, C15 NX36 > Jonathan Swift Street, Trim, Co Meath, C15 NX36 > —— > M +353 87 688 5964 T +353 46 942 2409 > https://gov.ie/opw > > —— > To send me files larger than 30MB, please use the link below > https://filetransfer.opw.ie/filedrop/[email protected] > > Email Disclaimer: > https://www.gov.ie/en/organisation-information/439daf-email-disclaimer/ > > —— > MSc GIS, FME Certified Professional > > —— > Oifig na nOibreacha Poiblí > Office of Public Works > > Sráid Jonathan Swift, Baile Átha Troim, Co na Mí, C15 NX36 > Jonathan Swift Street, Trim, Co Meath, C15 NX36 > —— > M +353 87 688 5964 T +353 46 942 2409 > https://www.opw.ie > > —— > Email Disclaimer: https://www.opw.ie/en/disclaimer/ >> -----Original Message----- >> From: Qgis-user <[email protected]> On Behalf Of Shinoto, PD >> Dr. Maria via Qgis-user >> Sent: 29 March 2022 22:25 >> 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
