3/18/18:
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For questions, contact gpsiono@jpl.nasa.gov and identify the source of data you are working with. 

Uploads of the jplg files are not yet complete. jpli files are as complete as possible right now. There is a missing day in 2015 (2015-09-09). Discpreancies were found for 2014-09-24 and 2014-08-18. These are being addressed.

Global ionospheric maps (GIM) for research
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GIM are global maps of total electron content, generated using techniques as described in references 1 and 2.

This area contains two data products: GIM with 15-minute cadence, based on 100 or 200 globally distributed GPS receivers (jpli*), and GIM with 2-hour cadence (jplg*) created using 35, 50 and 100 globally distributed sites. The files are in netcdf format and should be self-documenting. Each file contains multiple epochs. The files are labeled by doy-of-year number and 2-digit year (e.g. jpliDOY0.YYi.nc).

jpli files span 2000-2015, and the jplg files span 1994 to 2014. These jplg files were generated specifically for the research described in reference 3. Uniform processing is used for the entire time span, for jplg files. 

The jpli maps are 15-minute cadence. That corresponds to 96 maps per file. Please use the first 96 maps in each file, that cover the full day. There is occasionally a 97th map, but if present this covers the next day.

There are slightly larger differences between day boundaries for maps in 2000-2002 (and some in 2003) than later years. The reason is that for earlier years, maps were processed using only one day's worth of data. In later years, maps used data from prior and next day to minimize day boundary effects. More precise information on this is forthcoming.

Other jplg files generated with 100 or 200 sites, including more recent periods,  can be found at: cddis.gsfc.nasa.gov under ionospheric products, in IONEX format. These files are also found at CDA Web (ps://cdaweb.sci.gsfc.nasa.gov/index.html/) under the "GPS" source type, in CDF format. 

Sample files are in the current directory.

Future plans
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Uncertainty estimates will be generated for these products. 

References
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(1) Mannucci, A. J., B. D. Wilson, D. N. Yuan, C. H. Ho, U. J. Lindqwister, and T. F. Runge (1998), A global mapping technique for GPS-derived ionospheric total electron content measurements, Radio Sci., 33(3), 565 582, doi:10.1029/97rs02707.
(2) Mannucci, A. J., B. Iijima, L. Sparks, X. Pi, B. Wilson, and U. Lindqwister (1999), Assessment of global TEC mapping using a three-dimensional electron density model, Journal of Atmospheric and Solar-Terrestrial Physics, 61(16), 1227 1236, doi:10.1016/s1364-6826(99)00053-x.
(3) Emmert, J. T., A. J. Mannucci, S. E. McDonald, and P. Vergados (2017), Attribution of interminimum changes in global and hemispheric total electron content, J. Geophys. Res. Space Physics, 54(3), 295 16, doi:10.1002/2016JA023680.

Cognizant:
Anthony J Mannucci (anthony.j.mannucci@jpl.nasa.gov)