Curve di livello "perfette" da nuvola di punti SLAM in QGIS

Contour lines from a point cloud can be a disaster: curls, pyramids, and spikes that don't represent anything real. The problem is almost always not the cloud itself, but the DTM you build on top of it, which carries classification outliers and amplifies them in the interpolation. In this episode of "QGIS in Action," I start with a point cloud acquired with SLAM, already classified as terrain-only, and show you step-by-step how to create clean, meaningful contour lines using QGIS 3.44 LTR. The workflow I follow is this: Import the LAS point cloud into QGIS and assign the reference system (it's always better to work in UTM than a geographic system); Subsampling to adjust the density to the desired equidistance; Creation of the DTM via triangulation with clipping to a polygon mask; First generation of contour lines (the spike problem becomes immediately evident) Median filter with GRASS's R.NEIGHBORS to smooth spikes without damaging the morphology Direct before/after comparison and optional vector smoothing on curves Some things to note: QGIS does not propagate the CRS during point cloud processing; it must be reassigned at each step. The median filter, if pushed too far, also smooths the morphological details you need (paths, slopes, slope variations). The result is not perfect, but it makes cartographic sense. Even with a less than clean starting cloud, this process produces a readable product that is representative of the terrain. 🎓 GTER TRAINING QGIS in Action is a project developed together with @GterGeomatica, trainers specializing in QGIS and geographic information systems. If you'd like to learn more about QGIS (basic, advanced, Python) or other geospatial topics, you can find their training offerings here: 👉 https://www.gter.it/formazione With the code 3DMETRICAGTER, you get a €30 discount on any course. Gter Telegram Channel → Updates and Geobreak (free events): https://t.me/geobreak 📢 SUGGESTED CONTENT? If you're working with QGIS and have a recurring problem or a workflow that isn't working for you, let us know in the comments. Let's get inspired for future episodes. 📬 CONTACTS LinkedIn → paolo.corradeghini Telegram → https://t.me/paolocorradeghini Email → [email protected] If you'd like to support 3DMetrica and its free content, you can do so on Patreon: www.patreon.com/3dmetrica 0:00 Intro 0:47 Importing the Point Cloud 2:00 3D View 3:17 QGIS Tools for Point Clouds 3:59 Subsampling 6:41 From Point Cloud to Raster DTM 8:20 Raster Clipping 10:32 First Contour Lines 11:50 DTM Filtering 13:03 Before/After Comparison 16:31 Vector Smoothing 17:40 QGIS in Action and GTER 19:37 Outro