initial gnss derived tec decoder

[BenjaminRuston]

build-group=https://github.com/JCSDA-internal/ioda/pull/1256

Description

This decodes a COSMIC-2 TEC file and puts it into IODA format.

This is related to the IODA PR: https://github.com/JCSDA-internal/ioda/pull/1256

Issue(s) addressed

Resolves #1504

Dependencies

List the other PRs that this PR is dependent on:

• [x] https://github.com/JCSDA-internal/ioda/pull/1256

Impact

Initial capability for TEC decoding from netCDF to IODA

Checklist

• [x] I have performed a self-review of my own code
• [x] I have run the unit tests before creating the PR

[BenjaminRuston]

@davidkuhl this is just a start, but see if I can get a functional decoder soon, could have short cut it but trying to be generally thorough in the creation of the initial prototype

would be good to get other TEC files from potentially other constellations beyond COSMIC-2 and make sure this is the latest format of the files

[BenjaminRuston]

adding letter to number follow WMO BUFR:

[BenjaminRuston]

@davidkuhl so I've added a function to compute the semi-accurate lat/lon from the ECF coordinates. Think this will be helpful as now the IODA file will contain the same required data as the other data types. The operator is fully welcome to not use these and proceed to use the ECF coordinates.

I've started the IODA PR too, added to this PR description think have a good proposal to go forward with

[BenjaminRuston]

@davidkuhl and Victoriya the xyz2llh was abstracted from here: https://gis.stackexchange.com/questions/265909/converting-from-ecef-to-geodetic-coordinates

[BenjaminRuston]

these data will use the international reference ionosphere and an interface will develop with this version: https://github.com/JCSDA-internal/pyiri-jedi