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TOPIC: Assigning bathymetry data to grid nodes

Assigning bathymetry data to grid nodes 13 years 8 months ago #343

  • konsonaut
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I use BlueKenue to generate the grid of my channel. The elevation of the banks and of the thalweg are well defined via 3D polylines. I used these polylines as outlines (model boundaries) and hard lines and generated a 2D grid. In Blue Kenue there is only the option to generate the grid via 2D polylines. This works well. But how can I further assign for example to the grid nodes of the grid outline the appropriate elevation data from my polylines?
Can I use the mesh from Blue Kenue then in Telemac without editing?

Any help is greatly appreciated,
Thank you,
Clemens
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Re:Assigning bathymetry data to grid nodes 13 years 8 months ago #344

  • jmhervouet
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Hello,

Blue Kenue creates files with the Telemac format called Selafin, which includes bathymetry, so there should be no problem (if I understand well). Another way would consist of correcting the bathymetry in Telemac-2d, by including subroutine corfon.f in your Fortran file.
In this subroutine setting a bathymetry of point 125 at -10. would be :

ZF%R(125)=-10.D0

There is also a function INPOLY in library bief which tells you if you are in a given polygon, that can be used for more complicated corrections.

Remember also that geometry files and results files are in the same format, so that a previous results file with corrected bathymetry may be used as a new geometry file, then corfon.f is no longer necessary.

Regards,

JMH
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Re:Assigning bathymetry data to grid nodes 13 years 8 months ago #345

  • konsonaut
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Thank you for the answer.

My problem is a little bit more basic. ;)

After the planar grid generation I have to assign to the grid nodes elevation data.
I could export the x-y grid coordinates to a gis software and there interpolate bathymetry data to the grid nodes. My question was, if there is a better and easier way in BlueKenue or also in Matisse without this exporting and importing operation. Further the grid nodes at my model boundaries should have the same elevation data as the polylines, with which I defined the model boundaries.

Regards,
Clemens
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Re:Assigning bathymetry data to grid nodes 13 years 8 months ago #348

  • jeremie
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Hi Clemens,

The trick in BlueKenue to add elevation to your mesh is to triangulate all your elevation data. This is done by creating a new Triangulation object (from the File menu I believe). You then drag-and-drop all relevant data (xyz points, topo contours, etc...). In the properties of the Triangulation object, you then have a button called Triangulate. This will generate a triangulation of your elevation data. You can view it by dragging it to a 2-D view.

The second step is to map this triangulation on your mesh layer. The elevations on the triangulation should be interpolated onto the nodes of your mesh. Verify this by viewing your BOTTOM or FOND layer in the 2d-view. Finally export it as SELFAIN object (bigendian).

Let me know if that works for you...
I can provide you with more detailed instructions if necessary.

jeremie
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Re:Assigning bathymetry data to grid nodes 13 years 8 months ago #349

  • jmhervouet
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OK, I don't know for Blue Kenue (maybe sbourban knows... and I'll ask the developer in Canada to have a look at this). For Matisse, the polylines would have to be generated inside the program, including their elevation, before generating the mesh, with constraints that the mesh must follow the polylines. It is probably too late if the mesh is already done.

JMH
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Re:Assigning bathymetry data to grid nodes 13 years 8 months ago #350

  • sebourban
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Indeed Blue Kenue can map a dataset (or a mesh/grid) onto another one (your mesh).

Please look through the manual - Blue Kenue is fairly user friendly so it should not be too much of a problem.

Here is the link.
www.nrc-cnrc.gc.ca/eng/ibp/chc/software/kenue/blue-kenue.html

Do not forget to save you final selafin file as Big-Endian ...

sebastien
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Re:Assigning bathymetry data to grid nodes 13 years 8 months ago #355

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Thank you very much for the answers!

I tried to map the elevation data to the grid from a scatter dataset, but BlueKenue didn`t accept this. Now it works!
BlueKenue is really great!

Clemens
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Re:Assigning bathymetry data to grid nodes 13 years 8 months ago #361

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triangulate your point set first (create new triangulation - drag your point set into the triangulation object), then click on the target object (your mesh) in the workspce and use tools->map. It will prompt you for your new triangulation.

hope this helps.

Sebastien.
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