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NetCDF with rotated coordinates

  • September 26, 2019
  • 8 replies
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monicarm
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I'm working on a project where I need wave models created in MatLab. I have download them but when reading I get rotated coordinates.

For some reason, wave models operate with rotated coordinate systems as opposed to conventional ocean models (rlat, rlon). How can I manage to read and rotate this data with FME?

 

Best answer by david_r

Is this concerning coordinate systems with rotated (offset) poles?

Unfortunately FME does not handle these very well out of the box, but there may be some workarounds.

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8 replies

david_r
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  • Best Answer
  • September 26, 2019

Is this concerning coordinate systems with rotated (offset) poles?

Unfortunately FME does not handle these very well out of the box, but there may be some workarounds.


monicarm
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  • September 27, 2019

Is this concerning coordinate systems with rotated (offset) poles?

Unfortunately FME does not handle these very well out of the box, but there may be some workarounds.

Yes, that's the problem. Here is a print screen:

 

 


monicarm
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  • Author
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  • September 27, 2019

Is this concerning coordinate systems with rotated (offset) poles?

Unfortunately FME does not handle these very well out of the box, but there may be some workarounds.

Yes, that's the problem. Here is a printscreen of the netcdf.

 

 

 


david_r
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  • September 27, 2019

There are a couple of hints and tips over at this post that you may want to take a close look at:

https://knowledge.safe.com/questions/43959/netcdf-rotated-coordinate-system-rlat-rlon.html

It includes a small python library that I wrote to calculate back and forth between rotated poles and regular lon/lat. It's fairly easy to incorporate the functionality into FME (PythonCaller) if you know a little Python.

Hope it can help.


monicarm
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  • September 30, 2019

There are a couple of hints and tips over at this post that you may want to take a close look at:

https://knowledge.safe.com/questions/43959/netcdf-rotated-coordinate-system-rlat-rlon.html

It includes a small python library that I wrote to calculate back and forth between rotated poles and regular lon/lat. It's fairly easy to incorporate the functionality into FME (PythonCaller) if you know a little Python.

Hope it can help.

Thanks @david_r. I had already read this question but I was just wondering if FME had already a new solution. I will take a look at it.


rob_m_esriuk
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  • March 24, 2021

There are a couple of hints and tips over at this post that you may want to take a close look at:

https://knowledge.safe.com/questions/43959/netcdf-rotated-coordinate-system-rlat-rlon.html

It includes a small python library that I wrote to calculate back and forth between rotated poles and regular lon/lat. It's fairly easy to incorporate the functionality into FME (PythonCaller) if you know a little Python.

Hope it can help.

David, I would be interested to look at the python, however time moves on and the safe site seems determined not to show me that link, has it been moved?


david_r
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  • March 24, 2021

David, I would be interested to look at the python, however time moves on and the safe site seems determined not to show me that link, has it been moved?

It probably went missing in The Great Forum Migration a few months back. Here's the file in question: https://www.dropbox.com/s/mib2t17nrs92k1t/rotated_grid_transform.py?dl=0


rob_m_esriuk
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  • March 24, 2021

David, I would be interested to look at the python, however time moves on and the safe site seems determined not to show me that link, has it been moved?

thanks David