open TELEMAC-MASCARET The mathematically superior suite of solvers

Hi,

I'm working with a large domain forced by TPXO. When the geometry file is in lat-lon with:
SPHERICAL COORDINATES = YES
SPATIAL PROJECTION TYPE = 3
GEOGRAPHIC SYSTEM =1

The results are good.

I want to add drogues to my simulation, but from my understanding, the coordinates in user_flot need to be in mercator. I can't work in UTM because my domain covers 2 zones.

I projected my geometry file in Mercator with a GIS software (only UTM and MTM are available in bluekenue). And change the keywords for:
SPHERICAL COORDINATES = YES
SPATIAL PROJECTION TYPE = 2
GEOGRAPHIC SYSTEM =5

But now, my results with TPXO are not good.

How can I add drogue to my simulation if I have a large domain forced with TPXO? I'm confused about the geographic system to use.

Thank you,

Karine

Hello Karine,

TELEMAC-2D and TELEMAC-3D have to work in plane projection like UTM, Mercator, Lambert.
If using SPHERICAL COORDINATES = YES and geometry files in longitude/latitude, the first thing done is to convert the coordinates in Mercator. From that step to the writing of results, everything is done in plane projections, that is why if you want to add drogues, you have to give their coordinates in Mercator projection. You can read the formula used for conversion in $HOMETEL/sources/utils/bief/read_mesh_coord.f subroutine.

FYI if using SPHERICAL COORDINATES = YES and tidal database like TPXO, you have to set GEOGRAPHIC SYSTEM = 5 as when every interpolation with tide is to be done in Mercator projection at that step (done after the 1st conversion explained at the beginning). Anyway, if not set to 5, it is automatically done with a warning message.

Hope this helps,

Chi-Tuan