Multiple band GNSS chipsets have just recently become more common. The GLONASS constellation was inactive for quite some time due to economic issues in Russia,

Multiple band GNSS chipsets have just recently become more common. The GLONASS constellation was inactive for quite some time due to economic issues in Russia, probably the reason it's seen slow adoption. Galileo is the only other GNSS system, but it's incomplete. Then there is the issue of different bands, and need for more complex antennas and LNAs. Most of the numbers I've seen for chipsets indicate that GLONASS support is still relatively unoptimized, power consumption for GLONASS acquistion is far higher than for GPS, but I'm not sure if that's simply a poor front end for the GLONASS frequencies, or if the signal/processing is significantly different. Beidou (China), QZSS (Japan/Australia) and IRNASS (India) are all regional systems with far smaller systems (3+ satellites), and in the case of IRNASS and QZSS, heavily augmented by ground based stations (). Development of low cost RTK (real time kinematics), giving centimeter precision in some cases, has really been driven on a large scale by the Japanese. There is some great reading (and heavy math) on the RTKLIB site, http://www.rtklib.com/rtklib_document.htm http://www.rtklib.com/rtklib_document.htm, not only about RTK, but GNSS in general. And things are going to get even more interesting with the data from the GRACE satellites, their gravity model will help improve position accuracy even further.