README file for the roti15min_jpl data set

The rate of TEC index (ROTI) [1, 2] 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 are provided in CDF format by Xiaoqing Pi of the Jet 
Propulsion Laboratory.
 
ROTI data are provided as global maps using a 2.5 x 5 degree (geographic 
latitude x longitude) grid. The median ROTI value is calculated in each bin. GNSS 
data contributing to the ROTI computation are primarily collected from the global 
network of International GNSS Service and the regional network of Continuous 
Operating Reference Station (CORS).  

References

1.	Pi, X., A. J. Mannucci, U. J. Lindqwister, and C. M. Ho, Monitoring of global 
ionospheric irregularities using the worldwide GPS network, Geophys. Res. Lett., 
24, 2283, 1997.

2.	Pi, X., F. J. Meyer, K. Chotoo, Anthony Freeman, R. G. Caton, and C. T. 
Bridgwood, Impact of ionospheric scintillation on Spaceborne SAR observations 
studied using GNSS, Proc. ION-GNSS, pp.1998-2006, 2012.