Cross-points in exported roughness Wasp map-QGIS Wasp scripting

[Truong Sinh]

Hi all,

I am currently working with Wasp scripting in QGIS and utilizing the “Get Worldcover land cover process” tool, followed by “Polygons to roughness lines” and “Save WasP roughness lines.” Upon reviewing the exported roughness WAsP map file, I have encountered several cross points errors. It appears these errors occur at points where two polygons with the same z0 value intersect.

I have a few questions regarding this issue:

Should we validate the roughness WAsP map using the WAsP Map Editor for dead-ends, cross points, and LFR-errors, or is this validation only necessary when importing a Rough-ASC map (*.asc)?
If validation is recommended and cross points errors are detected in the WME, what steps can we take in QGIS to resolve these errors before exporting?

Best regards,

[Rogier]

Yes we recommend always checking with the map editor, but in principle there should be no errors. Could you share your map? Sometimes errors can be solved with "snap geometries to layer" in qgis.

[Truong Sinh]

Hi Rogier, 

Please see map in this link: https://drive.google.com/drive/folders/19XUF6dFftUT-LeOY1R8szx7LWpnkqsIJ?usp=sharing

Many thanks

[Rogier]

I tried to open your map, but I can see you have used 50 m resolution, so it takes hours to open in the map editor. I would recommend just using the default 100 m resolution, because it will be much faster to open and it will likely make very small differences only for WAsP, which is anyway simplifying the roughness map afterwards. I couldn't detect any errors in the map editor though, see below. Maybe make sure you use the latests version of the map editor and the QGIS plugin?

[Truong Sinh]

When I load the roughness WAsP map, a popup window appears with the following information:
"A "twin-line node" - with a pair of matching roughness lines - is encountered, at: (.....)
It can readily be resolved by joining the two lines. 
It is recommended to resolve twin-nodes automatically.
Do you accept auto twin-line node resolving by joining the matching roughness lines?"
When I clicked “No,” it displayed the Cross points error. When I clicked “Yes,” I saw the same result as in your previous capture. 

Thank you for your clarification and suggestion on resolving this issue.