open TELEMAC-MASCARET The mathematically superior suite of solvers

Hello,

I have a little problem with BlueKenue.
I have a set of data representing 3d UTM coordinates of the bottom of a channel, you can see a plan view of them in the 'image1' attached. I've imported these data as .xyz file in BlueKenue. The problem is that when I plot this points, somehow the y-coordinates change, so that many points appear aligned at the same y-coordinate (see 'image2').
My question is: is this only a plotting error not affecting the data themselves? Could this problem due to the fact that the y-coodinate is O(10⁶) whereas the x-coordinate is O(10⁵)?
I need to build a mesh and selafin file using this bathymetry so I want to make sure that the data that BK uses are the original ones.

Thank you

Hi fsinisa

You are not the only one to have this problem

Martin has explained the situation in his posting 5626 under “Flat triangles in mesh generated with Blue Kenue”.

Don’t worry the data is still good, it is only the visual display which looks funny (you can check the xyz data in a text editor). But you may have problems later with Telemac if the mesh is very fine, since it uses only a single precision for the node coordinates

Your best solution is to do a coordinate shift into a local system, instead of global UTM system

Use Edit→Shift X/Y

Thierry

Hello,

This has been discussed previously in a number of posts.

You are seeing the limits of (4 byte) floating point resolution.

See posting #6900

Martin

Thanks both for your quick replies!