Perito, I don't know where you are getting your points file. But here are some suggestions.
Often stepped DEMs are a result of someone starting with a scanned or vector contour map and then transforming that to a DEM using somewhat unsophisticated algorithms. So how to get rid of these. You can create a a file of points by generating random points (v.random) and assigning them elevation values from your DEM. Then you can use an interpolation algorithm like v.surf.rst or v.surf.bspline. Random points can help get rid of the steps. The fewer points, the smoother the DEM. More points will provide more topographic detail but may also show up some steps. Michael _____________________________ C. Michael Barton Associate Director, School of Complex Adaptive Systems (https://scas.asu.edu<https://scas.asu.edu/>) Professor, School of Human Evolution & Social Change (https://shesc.asu.edu) Director, Center for Social Dynamics & Complexity (https://complexity.asu.edu) Arizona State University Tempe, AZ 85287-2701 USA Executive Director, Open Modeling Foundation (https://openmodelingfoundation.github.io<https://openmodelingfoundation.github.io/>) Director, Network for Computational Modeling in Social & Ecological Sciences (https://comses.net) personal website: http://www.public.asu.edu/~cmbarton Message: 1 Date: Mon, 14 Aug 2023 13:12:06 +0200 From: bonushenricus <bonushenricu...@gmail.com> To: grass-user@lists.osgeo.org Cc: Corey White <corey.wh...@openplains.com> Subject: [GRASS-user] How can I remove steps artefacts in digital elevation model? Message-ID: <858b21a54b3a408cb954aa95af6fc417d8845936.ca...@gmail.com> Content-Type: text/plain; charset="UTF-8" Hello everyone I have a problem with an artefact in the dem I build from the data as a geopackage here https://urldefense.com/v3/__https://www.dropbox.com/scl/fi/7vzgupxszpg2sw7ib08p4/point_survey.gpkg?rlkey=7u1bv3rx8vcvkruq6z8zeezf0&dl=0__;!!IKRxdwAv5BmarQ!dDwnto4XTrla3t-Qm6io55iEpTu0vsDyIToUu1CfbK_lJOAaKZSQ7PZKdKEpGiP2nz-7FV0ZOR_HNX9Kn85pcW48Awtkw3dOGWE$ the problem has already described here https://urldefense.com/v3/__https://www.mail-archive.com/grass-user@lists.osgeo.org/msg40869.html__;!!IKRxdwAv5BmarQ!dDwnto4XTrla3t-Qm6io55iEpTu0vsDyIToUu1CfbK_lJOAaKZSQ7PZKdKEpGiP2nz-7FV0ZOR_HNX9Kn85pcW48AwtkUhCwWsE$ in which I had operated with "v.surf.rst --overwrite input=point_survey zcolumn=z elevation=dem mask=MASK tension=36. smooth_column=rms segmax=500 npmin=600 dmin=0.5 dmax=5" First of all I deleted dmax from v.surf.rst. Now I have tried raising the tension, even by a lot, but it does not change. I tried lowering the tension, but the steps still occur. Then I tried v.surf.rst on a higher resolution, at 5 cm, and then resample to 20 cm. I tried with r.resample.interpol, r.resample.rst and r.resample.tsp, with various parameters, various interpolation methods, various tensions or various smoothness indices, but I was unable to create a profile without these artefacts, which are in the order of only a few centimetres, but enough to create problems in the simulation with r.sim.water. I finally tried another approach: I created the contours, transformed the vector to raster, at a resolution of 5 cm (to get thin contours) and then used r.fillnulls to a 20 cm resolution region. With method=rst (which is the default) it gives me an error: "Growing NULL areas Assigning IDs to NULL areas Processing 1 map holes Filling hole 1 of 1 ERROR: Invalid input <n=n+0>" With method=bicubic it works but makes the steps. r.resample.bspline create other artefacts at the limit of the calculation regions. I should probably try anisotropy in v.surf.rst? Anyone have a solution? Thank you thank you!! -- -- Perito agrario Enrico Gabrielli progetto F.A.R.M. https://urldefense.com/v3/__http://www.farm-agroecologia.it__;!!IKRxdwAv5BmarQ!dDwnto4XTrla3t-Qm6io55iEpTu0vsDyIToUu1CfbK_lJOAaKZSQ7PZKdKEpGiP2nz-7FV0ZOR_HNX9Kn85pcW48AwtkWH0kupA$ Tessera n. 633 Collegio Periti agrari prov. Di Modena Biblioteca agricoltura: https://urldefense.com/v3/__https://www.zotero.org/groups/aplomb/__;!!IKRxdwAv5BmarQ!dDwnto4XTrla3t-Qm6io55iEpTu0vsDyIToUu1CfbK_lJOAaKZSQ7PZKdKEpGiP2nz-7FV0ZOR_HNX9Kn85pcW48AwtkXUVnt_I$ https://urldefense.com/v3/__https://www.inaturalist.org/observations/bonushenricus__;!!IKRxdwAv5BmarQ!dDwnto4XTrla3t-Qm6io55iEpTu0vsDyIToUu1CfbK_lJOAaKZSQ7PZKdKEpGiP2nz-7FV0ZOR_HNX9Kn85pcW48Awtk8hUdvyA$ ------------------------------ Subject: Digest Footer _______________________________________________ grass-user mailing list grass-user@lists.osgeo.org https://urldefense.com/v3/__https://lists.osgeo.org/mailman/listinfo/grass-user__;!!IKRxdwAv5BmarQ!dDwnto4XTrla3t-Qm6io55iEpTu0vsDyIToUu1CfbK_lJOAaKZSQ7PZKdKEpGiP2nz-7FV0ZOR_HNX9Kn85pcW48AwtkXgPmqO0$ ------------------------------ End of grass-user Digest, Vol 208, Issue 12 *******************************************
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