“…Occurrence of LSTIDs is generally related to geomagnetic activity, and they travel from the polar regions toward the equator, while MSTIDs are typically observed at midlatitudes during both quiet and disturbed conditions. Further, MSTID and LSTID characteristics were investigated using dense GPS receiver networks in Japan [e.g., Saito et al, 2001;Shiokawa et al, 2002;Tsugawa et al, 2003;Tsugawa and Saito, 2004;Nishioka et al, 2009;Hayashi et al, 2010], North America [e.g., Nicolls et al, 2004;Tsugawa et al, 2007;Kotake et al, 2007;Onishi et al, 2009], and less dense GPS networks in Europe [Borries et al, 2009;Jakowski et al, 2012;Otsuka et al, 2013] and China [Song et al, 2013;Ding et al, 2014]. Since mid-1990s, ground-based segment of the Global Positioning System (GPS) started to grow up extensively from several hundred stations worldwide to more than 6000 stations today.…”