open TELEMAC-MASCARET The mathematically superior suite of solvers

I'm rather new to TELEMAC (running v7p2).

I want to run a tidal simulation on the coast of Maine. I figured I could download data from TPXO, however:

1) I don't know the ZONE NUMBER IN GEOGRAPHIC SYSTEM or where to find it.
2) The files I downloaded don't have any extensions. I was going to call them in the steering file like:
BINARY DATABASE 1 FOR TIDE = h_EC2010
BINARY DATABASE 2 FOR TIDE = UV_EC2010
Something tells me this won't work.

Hello

1 - The ZONE NUMBER IN GEOGRAPHIC SYSTEM depends on the GEOGRAPHIC SYSTEM keyword. Look for these keywords in telemac2d.dico for detailed explanation.

2 - Files don't need to have an extension. The operating system only uses extensions to determine which program it will use to open a file. Apart from that, it's just part of the name of the file. And since Telemac will use the file name as provided in the steering file, this will certainly work.

Best regards,

Phelype

Hi, Thanks for replying.

OK, sorry for having to be led by the hand on this one, but the .dico file isn't exactly clear about geographic systems and zones.
I found this:
'-1="NO DEFAULT VALUE. CHOOSE THE NUMBER AMONG THE POSSIBLE CHOICES"';
'1="LAMBERT 1 NORTH"';
'2="LAMBERT 2 CENTER"';
'3="LAMBERT 3 SOUTH"';
'4="LAMBERT 4 CORSICA"';
'22="LAMBERT 2 EXTENDED"';
'30="UTM ZONE, E.G."

If I download the TPXO data for the Eastern US, where do I find the geographic zones?
Or, maybe my ideas about the mesh are screwed up. I'm analyzing the flow through a channel, which I just meshed myself with Blue Kenue (there's just an inlet and outlet). Is there some overarching geographic information I need to pull and add to the mesh and the geometry?

Hello

This configuration depends solely on the way you generated the mesh.

TPXO needs these information to convert the coordinates of your mesh to Lat x Lon, in order to find the appropriate data to use in your mesh. If your mesh is already in Lat x Lon, then no conversion is needed, otherwise TPXO will use the ZONE NUMBER IN GEOGRAPHIC SYSTEM to correctly convert the coordinates to Lat x Lon.

First you have to know the GEOGRAPHIC SYSTEM, that will be one of the following:
The ZONE NUMBER IN GEOGRAPHIC SYSTEM will depend on the previous configuration:

• If the GEOGRAPHIC SYSTEM is 1 (WGS84 LONGITUDE/LATITUDE IN REAL DEGREES), then the zone number will not be used.
• If the GEOGRAPHIC SYSTEM is 2 or 3, then the zone number is the number of the UTM zone (attachment). In your case the GEOGRAPHIC SYSTEM would be 2 and the ZONE NUMBER IN GEOGRAPHIC SYSTEM would be 19.
• If the GEOGRAPHIC SYSTEM is 4 then the zone number is one of the file values listed corresponding to each Lambert projection.
• I don't know what convention is the "MERCATOR FOR TELEMAC" system. Someone else has to answer that.

What you have to do is to find out what coordinate system your mesh is on and supply the correct value for the keywords.

Best regards,

Phelype

Thanks!

I generated the mesh in Blue Kenue and I didn't define any latitude or longitude.

So, if I understand you, (and I like repeating back things to make sure I get them):
I need to actually run TPXO's software to get the geographic zone number.
Alternatively, in the steering file I can preclude the geographic zone number (or just use the one you gave me) and define the latitude and longitude of the mesh.

Did you attach any file (concerning UTM), because I didn't see any in your reply?

The "Definition of Latitude or Longitude" is simply the coordinates your mesh are on.

I haven't seen you mesh, so I can't help much but, for the sake of the example, let's say your study area in in Portland, ME. If the coordinates of the mesh nodes are around (-70.266494, 43.672662) then you mesh is in Lat x Lon, so GEOGRAPHIC SYSTEM = 1 and ZONE NUMBER IN GEOGRAPHIC SYSTEM does not matter. If the coordinates are around (397902.980,4836296.444) then GEOGRAPHIC SYSTEM = 2 and ZONE NUMBER IN GEOGRAPHIC SYSTEM = 19. And similarly for the Lambert projections.

There's no "TPXO software" to run. The zone number depends on the geographic projection you used to build your mesh on. And that generally comes form the outline database you used. Just check the source of the outline and you'll probably find out what projection it uses. That is, of course, if it's not in Lat x Lon. Usually large coastal outline databases come in Lat x Lon.

Sorry, but I'm not able to help you any further without more details. You'll have to check the data you used to generate the mesh and find out the correct configuration.

Hello,

OK, so I attached my bathymetry and contour files. They're not great or that detailed; I'm just using them to learn the programs.

I didn't use any sort of latitude or longitude coordinates for the mesh. I took an arbitrary point and made it the origin (0,0), and then created the contour by measuring everything from this one point.

Basically, if I go back and I redo the contour and mesh, and for the coordinates, I use longitude and latitude, I can just set GEOGRAPHIC SYSTEM = 1 and everything should be hunkdory?

By the way, thanks for leading me through this. I just haven't found any good documentation. I hope that if I get good enough, I'll create a little manual so all of this is easily spelled out.

Yes, in this case you have to re-create your mesh using the correct Latitude and Longitude, then you'll be able to use data from TPXO. The thing about TPXO (maybe you know that, but just in case) is that it is a global database and relies on the geographic position of your domain to correctly get the tidal data for your simulation.

There is a brief description of these keywords in the Telemac3D user manual (page 35).

P.S.: I forgot (twice) to attach the image of the UTM grid. The advantage of using UTM over Lat x Lon is that it uses metric coordinates. The other way around, there is no need for conversion and a large study area can be easily meshed. Choose what best suit your needs.