Nice to know you got it! Nicolas Cadieux Ça va bien aller!
> Le 16 mai 2020 à 06:13, Priv.-Doz. Dr. Maria Shinoto > <maria.shin...@zaw.uni-heidelberg.de> a écrit : > > Hi, > > I had some intensive learning during the last days, and thanks again for your > help. > > After all it turns out that it is something Nicolas wrote, it is a matter of > the projection. The Japanese software just exported to a projected format, > but the original data seem to be in lat long. I found a way to get the > unprojected data and now can create a beautiful hillshade in an unprojected > lat long layer. And it even looks good in a projected project (EPSG:6670) > with on the fly projection. > > For hydrological analyses I need to use the projected data, but the artifacts > do not matter here. While binge-watching YouTube videos I realized that these > artifacts occur with the pros as well when they use the projected layers for > their analyses. Now everything much better and "in place". > > Best, > Maria > > >> Am 15.05.2020 um 13:21 schrieb Nicolas Cadieux >> <nicolas.cadi...@archeotec.ca>: >> >> >> >> Nicolas Cadieux >> Ça va bien aller! >> >>>> Le 14 mai 2020 à 23:12, Nicolas Cadieux <nicolas.cadi...@archeotec.ca> a >>>> écrit : >>> >>> Hi, >>> >>> >>> See below for comments. >>> >>> Nicolas Cadieux >>> Ça va bien aller! >>> >>>> Le 14 mai 2020 à 22:21, Priv.-Doz. Dr. Maria Shinoto >>>> <maria.shin...@zaw.uni-heidelberg.de> a écrit : >>>> >>>> Hi again, >>>> >>>> and sorry for the ongoing discussion. >>>> >>>> Today I exported a selection of the DEM data to a shapefile, just 9MB for >>>> the main file, and this makes testing very fast. >>>> >>>> (A) TINs did not work. >>> >>> TIn interpolation has memory problems with large data sets. Same problem >>> since QGIS 2x at least. It was cool features but is not made to handle >>> today’s data sets. >>>> >>>> (B) I tried all steps carefully again, but even the GDAL raster is >>>> horrible now. >>>> >>>> Here are some screenshots with my explanation and the protocol for >>>> rasterization and filling nodata. >>>> >>>> It seems that the artifacts are due to no data fields that evolve during >>>> rasterization as a pattern. These nodata fields may be due to a slight >>>> inclination of the grid from the export of the data with the Japanese >>>> software. >>>> >>>> 1) The point grid, one can see the inclination >>>> >>> <01.jpeg> >>>> >>>> >>>> 2) The raster of the same area, one can see the points of the vector point >>>> grid along the white empty space; this is NODATA. >>>> >>> <02.jpeg> >>>> >>>> >>> I would use gdal_grid not rasterize. Use Gdal grid with a larger search >>> circle will solve this problem. Use nearest neighborhood with a search >>> radius larger than the pixel (like 7m). That will reduce the no data. >>> Click on the help or go to the gdal website. That will help you add the >>> missing parameters like the -txe and -tye. (The extent) and the -outsize >>> for the number of pixels. >>> >>>> I add the protocol >>> <2020-05-15-rasterize-protocol-for-selection.txt> >>>> >>>> >>>> >>>> 3) Using the Fill NODATA from the Raster menu makes a beautiful looking >>>> raster, there seem to be no flaws. >>>> >>> <03.jpeg> >>>> >>>> >>> >>> That fixes things but adds new data to the raster. This may be unwanted. >>> >>>> I add the protocol. >>>> >>> <2020-05-15-fill-nodata-protocol-for-selection.txt> >>>> >>>> >>>> 4) This is the same area as in (3), but instead of a pseudocolor ramp >>>> shown as hillshade. >>>> >>> <04.jpeg> >>>> >>>> >>> This is normal if you select a bad z factor (probably not the case here). >>> You will have the same thing if you zoom in and have nearest neighbour in >>> the “zoomed in” under “resampling“ in the hillshade symbology window. >>>> >>>> 5) This is the impression from a larger area. >>>> >>> <05.jpeg> >>>> >>>> >>>> >>>> 6) This is the same small area hillshaded with the GDAL tools. Looks good, >>>> but suffers from the same artifacts. >>>> >>> >>> No this is way it should look like (Image under). You can see the pixels >>> because you are zoomed in. Again, select the correct z factor (if x,y are >>> in long -lat and z is in meters or feet.) (probably ok here). >>> >>> <06.jpeg> >>>> >>>> >>>> >>> Play with the resampling zoomed out parameters in symbology >>> >>> >>>> 7) The larger area from hillshade in GDAL tools. >>>> >>> <07.jpeg> >>>> >>>> >>>> >>>> >>>> >>>> I sorry to be so insisting on the problem, I think it is not the problem >>>> of QGIS, but perhaps there are solutions to such a case. -- The projection >>>> is OK, and the base map fits perfectly. >>>> >>>> Best and Thanks to anyone trying to help, >>>> Maria >>>> >>>> >>>> >>>> > _______________________________________________ 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
