Re: [Qgis-user] Create contours algorithm does not work

Roland Spielhofer via QGIS-User Thu, 05 Oct 2023 03:23:27 -0700

Just wanted to add that I also tried the latest gdal_contour CLI command - with the same result.

gdalinfo of the raster-tif says:

Driver: GTiff/GeoTIFF
Files: Axx_PPS_1_0000_Z.tif
Size is 1291, 3701
Origin = (590694.146499999915250,5311061.004799999296665)
Pixel Size = (0.050000000000000,-0.050000000000000)
Image Structure Metadata:
INTERLEAVE=BAND
Corner Coordinates:
Upper Left ( 590694.146, 5311061.005)
Lower Left ( 590694.146, 5310875.955)
Upper Right ( 590758.696, 5311061.005)
Lower Right ( 590758.696, 5310875.955)
Center      ( 590726.421, 5310968.480)
Band 1 Block=1291x1 Type=Float32, ColorInterp=Gray
Min=312.351 Max=314.506
Minimum=312.351, Maximum=314.506, Mean=313.375, StdDev=0.602
NoData Value=-99999
Metadata:
    STATISTICS_MAXIMUM=314.50564575195
    STATISTICS_MEAN=313.37469987748
    STATISTICS_MINIMUM=312.35101318359
    STATISTICS_STDDEV=0.60238892993285

Anything wrong with it?

It has been generated by SAGA by rastering a pointcloud.

Regards,

Roland

Gesendet: Mittwoch, 04. Oktober 2023 um 16:44 Uhr
Von: "Roland Spielhofer via QGIS-User" <[email protected]>
An: "QGIS User" <[email protected]>
Betreff: [Qgis-user] Create contours algorithm does not work

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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Re: [Qgis-user] Create contours algorithm does not work

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