Use of different GNSS for positioning
With the Chinese GNSS Beidou a fourth GNSS became available for worldwide positioning purposes. In July 2020 Beidou has officially completed its constellation. This sparks patriotism especially in China and apparently quite a number of users download applications onto their smartphones for using Beidou in navigation (abacus 2020).
The hurdles are the same for all and especially those being patriotic by using “their” GNSS. First of all, a constellation requires enough satellites in a favorable constellation. The same as with GPS only in “ancient” times when GPS started out with initial set of satellites.
At next the observations have to have a good quality. Beidou and also Galileo have the advantage of having the better start since the science moved on from early start of GPS. However, phones must be able to support also signals from those newer systems. Recent phone chipsets like the Snapdragon 855 do so, but even then, the chipsets provide the best estimate based on all signals.
Depending on the actual phone manufacturer the raw observation set is provided through the Android API. The delivery of raw observations allows the separation of observations by GNSS and allow a parallel computation of navigation positions in different combinations.
The next possible difference is the supported signals per GNSS. Most advanced phone chips allow dual-frequency GPS and Galileo observations, but only single-frequency observations for GLONASS and Beidou.
The example given here is showing the different positioning results using all four GNSS independently and at the bottom the combined solution of all GNSS in one solution.