I'm trying to figure out a way to map water depth data from a coarse triangular mesh cell onto a high resolution (HR) raster (in .asc format). My coarse model and the raster are 2D.
I created a very coarse (<-- intended) mesh for an urban flooding simulation by polygonizing a high resolution digital elevation model, smoothening the edges (using QGIS) and then meshing it (using gmsh).
Then I did the flooding simulation and now I have some results for the mesh in .vtu format. For each cell I have a water elevation and a bed elevation value (--> substract the latter from the former to get water depth). The water elevation is of course higher than the bed elevation of a cell.
As mentioned the grid is coarse, I have big cells, for example let's say a cell is 100 m in characteristic length. The HR raster is very fine.
In a next step I'd like to get some water depth results (= water elevation - bed elevation). I already have results just for the coarse grid. But now I'd like to take my water elevation value from a coarse cell and the underlying bed elevation data from the HR model and compute the water depth this way.
The following sketch might elaborate my undertaking a little better
I have a couple of problems doing this:
Is this actually the right forum for this kind of task :D? Because I don't know if QGIS is capable of doing this, or if I only need something like ParaView for this task. The raster calculator might come in handy I thought.
If QGIS fits for me, how do I get the .vtu data into QGIS? This would be nice because I could create the water depth for all cells but if it's not possible I'd just replicate a couple of cells as triangles in QGIS and give them the water elevation data by hand.
(I've seen a couple of questions concerning QGIS and VTK that go in the same direction and I will check them out now.)
- If all of that should work out, how can I actually compute the water depth? My first thought would be to use the raster calculator to compute the difference between water elevation and bed elevation and create a new raster that has the resulting water depth as information on each raster point.
I've now managed to create a polygon with cell IDs and corresponding water elevations in QGIS. I used a gmsh plugin for QGIS and extracted the elevation data with ParaView into a CSV-File. I then created a table join within QGIs for the Cell IDs and their respective water elevation levels. Now I only need to use the raster calculator. Does anyone have an idea how I could compute the wanted water depth?