Hi,
I have a 1-band raster representing the surface of a road - the pixels hold the z-values/elevation.
I have loaded it into QGIS and used "contours" as renedering method. The result looks good, I additionally have the same raster with hillshading as rendering - very pleasent - see
https://imgur.com/XMmMmdj
the fuzzy black lines are the contours, the light area is the hillshaded z-raster.
 
One drawback of the on-the-fly contours is that they are limited to a minimum interval of 0.1 m. As the surface is very flat (a road), I would like to have a more dense set of contours (0.02 m, e.g.).
 
I tried the contours function (GDAL > Raster extraction > contours) from the processing toolbox. It created a new layer with a plausible number of lines, but the lines are not visible, no matter what I try. The log of Contour is below - I do not see anything special.
I tried to calculate the length of the geometries, but I get "nan" for each.
 
Any ideas why the contours function does not produce meaningful output while the rendering as contours works beautifully?
 
Kind regards,
Roland
 
 

QGIS version: 3.32.1-Lima

QGIS code revision: 4a078ecf63

Qt version: 5.15.3

Python version: 3.9.5

GDAL version: 3.7.1

GEOS version: 3.12.0-CAPI-1.18.0

PROJ version: Rel. 9.2.1, June 1st, 2023

PDAL version: 2.5.5 (git-version: a7569c)

Algorithm started at: 2023-10-04T16:39:30

Algorithm 'Contour' starting…

Input parameters:

{ 'BAND' : 1, 'CREATE_3D' : False, 'EXTRA' : '', 'FIELD_NAME' : 'ELEV', 'IGNORE_NODATA' : False, 'INPUT' : 'Q:/RoadSTAR/Archiv/_Diverses ohne Proj.Nr/A02_Detailauswertung/A02_2-1_km28,080_km27,694___230713_1758/A02_2-1_KM28,147_KM27,957_230713_1758/GeoTIFF/A02_2-1_KM28,147_KM27,957_230713_1758_PPS_1_0000_Z.tif', 'INTERVAL' : 0.1, 'NODATA' : None, 'OFFSET' : 0, 'OUTPUT' : 'TEMPORARY_OUTPUT' }

 

GDAL command:

gdal_contour -b 1 -a ELEV -i 0.1 -f "GPKG" "Q:\\RoadSTAR\\Archiv\\_Diverses ohne Proj.Nr\\A02_Detailauswertung\\A02_2-1_km28,080_km27,694___230713_1758\\A02_2-1_KM28,147_KM27,957_230713_1758\\GeoTIFF\\A02_2-1_KM28,147_KM27,957_230713_1758_PPS_1_0000_Z.tif" C:/Users/lokaladmin/AppData/Local/Temp/processing_lqTuzZ/d902fb853ce246a59f2768d2f0607ba6/OUTPUT.gpkg

GDAL command output:

0...10...20...30...40...50...60...70...80...90...100 - done.

Process completed successfully

Execution completed in 0.39 seconds

Results:

{'OUTPUT': 'C:/Users/lokaladmin/AppData/Local/Temp/processing_lqTuzZ/d902fb853ce246a59f2768d2f0607ba6/OUTPUT.gpkg'}

 

Loading resulting layers

Algorithm 'Contour' finished

 
 
https://imgur.com/XMmMmdjhttps://imgur.com/XMmMmdjhttps://imgur.com/XMmMmdjhttps://imgur.com/XMmMmdjhttps://imgur.com/XMmMmdjhttps://imgur.com/XMmMmdj
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