Japan has some challenges with traditional GPS and satellites that can be low on and buildings interrupt the signal. https://en.wikipedia.org/wiki/Quasi-Zenith

Japan has some challenges with traditional GPS and satellites that can be low on and buildings interrupt the signal. https://en.wikipedia.org/wiki/Quasi-Zenith_Satellite_System https://en.wikipedia.org/wiki/Quasi-Zenith_Satellite_System > The Quasi-Zenith Satellite System (QZSS), also known as Michibiki (みちびき), is a four-satellite regional satellite navigation system and a satellite-based augmentation system developed by the Japanese government to enhance the United States-operated Global Positioning System (GPS) in the Asia-Oceania regions, with a focus on Japan. ... > The primary purpose of QZSS is to increase the availability of GPS in Japan's numerous urban canyons, where only satellites at very high elevation can be seen. A secondary function is performance enhancement, increasing the accuracy and reliability of GPS derived navigation solutions. The Quasi-Zenith Satellites transmit signals compatible with the GPS L1C/A signal, as well as the modernized GPS L1C, L2C signal and L5 signals. This minimizes changes to existing GPS receivers. Its got a neat orbit that does a figure 8 with the apogee over Japan (see also https://en.wikipedia.org/wiki/Tundra_orbit https://en.wikipedia.org/wiki/Tundra_orbit )