Last week’s discussions in the GIS community revolved around practical applications and emerging challenges. Members shared experiences and resources for tackling peak-hour traffic calibration, ensuring models reflect real-world conditions. There was a keen interest in courses that enhance skills in spatial crime analysis, a growing field that blends GIS with criminology. Additionally, converting CityGML to 3D Tiles was a hot topic, with discussions focusing on reliable methods for maintaining data integrity during the transformation process.
This Week’s Hot Topics
Practical resources for peak-hour route calibration
This conversation centers on tools and techniques to fine-tune models for peak-hour traffic. It’s essential for those looking to improve the accuracy of transportation planning. Read more here
Best courses for spatial crime analysis
Participants are exchanging recommendations for courses that blend GIS with criminology. It’s an invaluable thread for anyone looking to enhance their analytical toolkit. Read more here
Reliable CityGML to 3D Tiles pipeline
This thread tackles the complexities of converting CityGML data to 3D Tiles, highlighting reliable methods and potential pitfalls. It’s a must-read for those working with 3D data transformations. Read more here
Thanks for keeping up with the latest conversations. Stay engaged and continue bringing your expertise to the discussions.
Quick tip: when transforming 3D multipatches or point clouds, always “set a vertical CS before you project” — ArcGIS Pro won’t touch Z unless both sides have a vertical coordinate system, so the ellipsoid-vs-orthometric gap (about 30 m in many areas) can sneak in. I keep a control point with a known elevation to sanity-check; if it’s off by about 30 m, you likely skipped the geoid correction (e.g., WGS84 ellipsoidal ↔ NAVD88 via a geoid model). If a proper vertical transform isn’t available, rescale Z for units first and run the 2D Project as a temporary workaround.
And ran into this moving multipatches from StatePlane to UTM; making sure Z units matched and running Convert Vertical Datum before Project fixed the “floating roofs” — don’t use Define Projection as a shortcut. @jking if textures or normals go weird, Repair Geometry first or export to a new FGDB; Esri’s note helps: Vertical coordinate systems—ArcGIS Pro | Documentation — anyone finding EGM2008 grids outperform NAVD88 in dense downtowns?
On a recent bridge model, setting the file geodatabase’s Z tolerance/precision to 0.001 m before loading the mesh stopped the ‘stair-step’ artifacts after reprojection. If you’re in QGIS/GDAL, exporting with double precision achieves the same effect, though the files get noticeably larger.