open TELEMAC-MASCARET The mathematically superior suite of solvers

Hi,

To get a better contextual understanding of the Donau example (among others), I'd like overlay it with other geospatial datasets. For this purpose, however, I needed the coordinate reference system (CRS) / projection of the SLF, which I cannot infer with any software (BlueKenue, QGIS, Janet). So I guess the SLF doesn't know its geospatial reference.

I also tried to look into the TUC papers and Telemac docs introducing this and other examples, and wild guessing of the CRS didn't work out neither.

Is there any possibility to get the CRS / projection of the examples, for instance, in the form of an EPSG code?

Best,
Sebastian

Hi Sebastian,

I have the same problem as you，have you found a solution yet?

Best,
WangHao

Hi,

After some investigation, I could not find any EPSG coordinate system for the donau example and others, too. There also is a useful tool to investigate the projection that best fits your coordinates at projfinder.com/

Anyway, the BAW data from the donau were very likely made from an unspecified reference point, as c.coulet suggested. Without the reference point, no transformation will be possible.

Best,
Sebastian

I had a quick look at the donau example.
EPSG 5243 with a translation of 110000 on X and -249000 on Y is a first approx that fit quite well (error ~100m).
Probably the EPSG choice is not the right one but i(m not familiar with German coordinate system...

Hi
Some of the examples had been built at a period where GIS was not commonly used...
So users didn't take care of the CRS / projection.
Data were available in a coordinate system which was often manually shifted to keep the precision compatible with the digits of coordinates values.
I think this test case was built by BAW (but not fully sure).
Maybe you could try to select the German coordinates system existing around 1990-2000 and see if a simple translation allow you to accurately place the model...

Hope this helps

Hi
I have another question.How can I generate a basic SLF file for Telemac computing? I can't find a way to generate it. I think there should be a step to add CRS/projection. in the process of generating this basic file.
Best,
WangHao

Hi,

During the SLF creation, you can use some georeferenced data, and I summarized two ways for georeferenced SLF creation here:
hydro-informatics.com/numerics/pre-slf-tm.html

Once you created the SLF, it is theoretically possible to reproject it, but I'd rather not do so: a reprojection may lead to distortions causing poor mesh quality (e.g., too narrow triangles).

Best,
Sebastian

Hi,

I'll give it a try,thank you very much
Best,

WangHao

Hi Sebastian, hi WangHao,

sorry for my late reply. The coordinate were shorten in order to use SERAFIN (and not SERAFIND). The full coordinates are too long for the SERAFIN format so that accuracy is not high enough.
So you need to move the coordinates to their original values:
x + 4500000
y + 5400000
Then the grid is in EPSG 31468 (GK4).

Best regards,
Rebekka