While the United States’ GPS is used in pretty much all vehicle navigation systems and smartphones, and Russia’s GLONASS is making inroads, not many are aware that China has been busy launching its own global navigation satellite system called BeiDou. Over the past three years or so, China has significantly expanded BeiDou and there are now more than 10 BeiDou satellites orbiting.
Here’s a skyplot taken in the recent months from a tracking station in Canberra. The orange dots are BeiDou satellites showing 7 of them being visible and tracked at that time.
Slightly different to GPS, GLONASS or Galileo, BeiDou consists of satellites with three different orbit patterns. In addition to GPS-like Middle Earth Orbit (MEO), it also features satellites with Inclined Geosynchronous Orbit (IGSO) and Geostationary orbit (GEO). IGSO satellites move in the sky on a figure-of-8 like pattern. Have a look at the plot below and you can visually identify those IGSO satellites (number 6,7, 8 and 9). The advantage of IGSO is that it stays high up in the sky for much longer than typical GPS satellites. This means better performance in urban canyon. The disadvantage is that it is not a worldwide coverage. So while users in China, Australia and all countries in their orbit footprint can enjoy satellite 6, 7, 8 and 9 for longer, users in other parts of the world, like the Americas, are not be able to track them at all. Though China is probably not too concerned about this.
The third type, geostationary (GEO) satellites, as the name suggests, always stay at the same spot in the sky. In the plot below, you can see all the BeiDou GEO satellites (number 1, 2, 3 and 4) hovering above the equator.