[ncl-talk] Reading in .ieeer8 file and plotting it with NCL

[Hughlett, Taylor M]

Hi Dave,

Thank you so much for the information. I was able to track down the file that has all of the descriptions I required, and am now working on reading it in using NCL!

Cheers,
Taylor M Hughlett, Ph.D.
UTA Earth and Environmental Sciences
500 Yates St.
Geoscience Bldg Rm 117
Arlington, TX 76013-0049

From: Dave Allured - NOAA Affiliate <dave.allured at noaa.gov<mailto:dave.allured at noaa.gov>>
Date: Wednesday, January 4, 2017 at 6:52 PM
To: "Hughlett, Taylor M" <taylor.hughlett at uta.edu<mailto:taylor.hughlett at uta.edu>>
Cc: "ncl-talk at ucar.edu<mailto:ncl-talk at ucar.edu>" <ncl-talk at ucar.edu<mailto:ncl-talk at ucar.edu>>
Subject: Re: [ncl-talk] Reading in .ieeer8 file and plotting it with NCL

Taylor,

> 2. How do I know what data is stored on the file prior
> to reading it in (i.e. Variables)? Or is this even possible?

Files called "binary" without additional qualification can only be understood by formal documentation, or by at least a minimal description from the person who created the file.  You need to get this description from the source of your data.  Typically there is no descriptive metadata stored inside such files, and the assumption is that this description is somewhere external.

The description should include file layout details such as array sizes, positions, dimension order of storage, elemental data type, byte order, fortran write mode if any, and record structure if any.  The description should also include what variables and possibly metadata are stored.  If the layout details are hard to get, it can sometimes help to find out just what software created the file.

The suffix .ieeer8 says to me, "8-byte reals", because only fortran uses the type name "real" instead of "float" or "floating point".  A fuller type description is "8-byte IEEE floating point values", but that is just a guess.  If correct, that would be NCL data type "double", and that does not answer any of the other questions about file layout.

--Dave


On Wed, Jan 4, 2017 at 1:47 PM, Dennis Shea <shea at ucar.edu<mailto:shea at ucar.edu>> wrote:
Were the data records written by fortran or
        See: http://www.atmos.washington.edu/~salathe/osx_unix/endian.html

or ?????

[0]
The problem with binary is that someone must describe how the data was written. Fortran's default (sequential) binary has **hidden record separators**. The user could also open a binary with "access=direct". This means 'flat' binary files (no record separators.

[1]
Were the binary files created on a big- or little-endian system? See: https://en.wikipedia.org/wiki/Endianness

[2]
Likely, fbindirread *or* fbinrecread would work. However, without more knowledge not much more can be said.

[3]
One major reason for the creation of HDF and netCDF to allow the files to be 'blindly' examined via a suite of standard function functions.



On Wed, Jan 4, 2017 at 1:30 PM, Hughlett, Taylor M <taylor.hughlett at uta.edu<mailto:taylor.hughlett at uta.edu>> wrote:
Good afternoon everyone,

I am attempting to read in a .ieeer8 file using NCL so that it can be plotted.

I am completely new with binary files, so bear with me.

I understand that this is a binary file, so visualization and reading it is much more complicated than it would be with netCDF's.

After having looked over the instructions on the NCL site, I am still having some confusion with how to get started.

Specifically, I have these questions:

  1.  Will the fbindirread work to read in a .ieeer8 file (I am assuming the file is fortran as it is a restart file for CESM1's POP2)?
  2.  How do I know what data is stored on the file prior to reading it in (i.e. Variables)? Or is this even possible?

Any help would be greatly appreciated with this, and I am happy to provide more information if it is required.

Thanks,
Taylor M Hughlett, Ph.D.
UTA Earth and Environmental Sciences
500 Yates St.
Geoscience Bldg Rm 117
Arlington, TX 76013-0049
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