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Visualization of tin-created DEMs in QGIS via threejs results in tall 'church-spiral-like' column?

Geographic Information Systems Asked by birdybird03 on March 21, 2021

I keep having this problem while doing a simple 3D visualization of my newly created DEM in QGIS via the threejs plugin.

I work in Balkan Zone 7 metric system and, when I try to visualise the DEM that I created from points (which were transformed in Balkan Zone 7) using the TIN interpolation method, I get a really, really tall ‘church-spiral-like’ column in my browser. I have to scroll all the way to the top just to see my visualization.

But, of course, if I change from metric to another CRS, I get flat terrain in my visualization while my threejs display’s the following message:

The unit of current CRS is degrees, so the terrain may not appear well.

The problem doesn’t seem to appear while working with free data like the ASTER GDEM or SRTM data for my country, no matter if they are set to WGS, Pseudo-Mercator or Balkan Zone 7, the topography and the terrain still appear well.

One Answer

I've seen this effect for data that is well above sea level (ie, 2500M). The plugin visualizes the extent of the canvas (unless you've clipped the DEM to a smaller extent in the dialog that pops up when you double click the DEM entry in the list). The background canvas is treated at 0' elevation, so the data is much above baseline. If you don't have this problem with other DEM data for the same region, I assume you're working close to sea level, which suggests that the data you created has an incorrect elevation. Check the range of elevations in your data compared to known elevations for the region in general.

Answered by Llaves on March 21, 2021

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