Re: [Qgis-user] Stream to feature problem
On 28/02/2020 2:12, ming han wrote: Hi all Is qgis has a function like "stream link" in Arcgis which can convert the stream raster to feature. I tried with raster to vector function in grass and qgis. it has following errors. Using GRASS, the way to do this involves two steps: first you want to "thin" the raster streams using the module "r.thin". This insures that there will not be adjacent pixels. Then, when you convert to stream lines, specify the type as line feature. So here are the commands (if you have a raster stream network called "streams"): r.thin streams output=streams_thin r.to.vect streams_thin output=streams_vector type=line In addition, I should mention that GRASS offers a set of plugins for hydrology: r.stream.*. Among them is the module r.stream.order. Using this plugin you can create a stream vector directly from the flow direction and flow accumulation grids, and you get the stream order and upstream flow accumulation area "for free". HTH Cheers Ming ___ Qgis-user mailing list Qgis-user@lists.osgeo.org List info: https://lists.osgeo.org/mailman/listinfo/qgis-user Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user -- Micha Silver Ben Gurion Univ. Sde Boker, Remote Sensing Lab cell: +972-523-665918 https://orcid.org/-0002-1128-1325 ___ Qgis-user mailing list Qgis-user@lists.osgeo.org List info: https://lists.osgeo.org/mailman/listinfo/qgis-user Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
Re: [Qgis-user] Stream to feature problem
Sorry, this message got messed up - trying again... Hi Ming, There is a place where your raster "line" is two pixels wide, and this is also where the "errors" occurs. I guess that the raster "line" needs to be properly thinned (to a one pixel wide skeleton) before running this algorithm. Håvard On 28.02.2020 09:09, Håvard Tveite wrote: > Hi Ming, > > The errors occur where raster "line" is two pixels wide, and > that is also where you find the "errors". > (to a one pixel wide skeleton) before running this algorithm. > > Håvard > > On 28.02.2020 01:13, ming han wrote: >> Hi all >> Is qgis has a function like "stream link" in Arcgis which can >> convert the stream raster to feature. >> I tried with raster to vector function in grass and qgis. it has >> following errors. >> >> Cheers >> Ming >> >> image.png > ___ Qgis-user mailing list Qgis-user@lists.osgeo.org List info: https://lists.osgeo.org/mailman/listinfo/qgis-user Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
Re: [Qgis-user] Stream to feature problem
Hi Ming, The errors occur where raster "line" is two pixels wide, and that is also where you find the "errors". (to a one pixel wide skeleton) before running this algorithm. Håvard On 28.02.2020 01:13, ming han wrote: > Hi all > Is qgis has a function like "stream link" in Arcgis which can > convert the stream raster to feature. > I tried with raster to vector function in grass and qgis. it has > following errors. > > Cheers > Ming > > image.png ___ Qgis-user mailing list Qgis-user@lists.osgeo.org List info: https://lists.osgeo.org/mailman/listinfo/qgis-user Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
