00README for GPS data at SPDF

This directory contains the GPS Total Electron Content (TEC) data produced by the 
International Global Navigation Satellite Systems Service (IGS) Ionosphere Working 
Group and by the Analysis Centers that have contributed to the IGS data including
CODE of the University of Bern (Switzerland), ESA of the European Space Operations 
Center (ESOC) in Darmstadt (Germany), JPL of the Jet Propulsion Laboratory, 
Pasadena (USA), and UPC of the University Politechnical Catalonia in Barcelona (Spain)
The IGS data are a computed as a weighted mean of the data from the four analysis
centers. A description and comparison of the different techniques can be found in:
M. Hernández-Pajares, J.M. Juan, J. Sanz, R. Orus, A. Garcia-Rigo, J. Feltens, A. 
	Komjathy, S.C. Schaer, and A. Krankowski, The IGS VTEC maps: a reliable source of 
	ionospheric information since 1998Journal of Geodesy (2009) 83:263–275
	DOI:10.1007/s00190-008-0266-1
Feltens, J., M. Angling, N. Jackson‐Booth, N. Jakowski, M. Hoque, M. Hernández‐Pajares, 
	A. Aragón‐Àngel, R. Orús, and R. Zandbergen (2011), Comparative testing of four 
	ionospheric models driven with GPS measurements, Radio Sci., 46, RS0D12, 
	doi:10.1029/2010RS004584
Peng Chen, Hang Liu, Yongchao Ma, Naiquan Zheng, Accuracy and consistency of different 
	global ionospheric maps released by IGS ionosphere associate analysis centers,
	Advances in Space Research, Volume 65, Issue 1, 2020, Pages 163-174,
	doi:10.1016/j.asr.2019.09.042.

CONTENT: 

The data were obtained from NASA's Crustal Dynamics Data Information System (CDDIS) 
that is distributing the data on behalf of the IGS Iono Group. The data are provided 
in daily files in CDF format. Each file includes the data from all 5 analysis centers
(IGS, CODE, ESA, JPL, UPC).

tec2hr_igs:
GPS-deduced 2-hour Total Electron Content (TEC) global maps and movies from IGS,
CODE, ESA, JPL, and UPC. Data start at June 1, 1998 and data production is ongoing. 

tec1hr_igs:
GPS-deduced 1-hour Total Electron Content (TEC) global maps and movies from 
UPC and ESA. Data start at Jan 15, 1998 and data production is ongoing.

tec15min_igs:
GPS-deduced 15-minute Total Electron Content (TEC) global maps and movies from 
UPC. Data start at Jan 15, 1998 and data production is ongoing.

movies:
Movies of global TEC maps for the time periods of two widely studied geomagnetic storms,
the Bastille Day storm on July 15–16, 2000 and the Halloween storm on October 28–29, 2003:
GPS_IGS_Bastille_movie.gif	2009-03-06 08:22 	1.3M
GPS_IGS_Halloween_movie.gif	2009-03-06 08:22 	3.3M

roti15min_jpl:
The rate of TEC index (ROTI) characterizes TEC fluctuations observed along 
receiver-to-satellite line of sight links over a 5-minute interval. The measurement 
is obtained by processing GNSS dual-frequency phase data and computing the standard 
deviation of the rate of TEC change over that interval after removing its background 
variation trend. The ROTI data were provided in CDF format by Xiaoqing Pi of the Jet 
Propulsion Laboratory and cover the time period Nov 29, 2012 to Nov 3, 2014. For more 
details please consult the 00README file in this subdirectory.

D. Bilitza --- Aug 26, 2020