Using Beidou in Europe
Beidou (北斗) is presently aimed at China as a navigation system. You can receive 北斗 satellites fine outside China. But the network of ground stations only provides corrections as far as they are relevant for China. Furthermore satellite coverage is much better over China than over the rest of the world.
北斗 comprises number of geostationary satellites at a static location over China, a number of satellites flying figure eight loops (in inclined geostationary orbits) and a relatively limited number of satellites in lower orbits which lead them all over Earth. Outside China you will therefore see less satellites than in China and the error corrections will not be as good.
Nevertheless you can
perfectly well use 北斗 now, especially in combination with the GPS
system. When used in combination you get better locations than using
GPS only. Simply because more satellites tend to be better when it
comes to satellite navigation.
I have tracked 北斗 satellites for a few months using my home-built Navspark receiver (see The Navspark satellite navigation receiver). I logged my location and some extra data like DOP values. I also logged which satelliets where used in the solution, their location relative to myself and the received signal power.
On the maps you can
see some of the first results. These images shows a maps with the
location record. For red points 2 or less 北斗 satellites were used
for the location, meaning a location cannot be computed with 北斗
alone. Blue points indicate 3 北斗 satellites were used, which is just
enough for a 2D location. For green points 4 or more satellites were
used in the location. In these locations one can compute a location
from the 北斗 system alone.
The second figure shows
the number of 北斗 satellites in view at a logged location. Note that
there is a limited number of locations with zero satellites in
view. Since one 北斗 geostationary satellite is in view from the
Netherlands this cannot be right. It merely reflects the fact that
sometimes the receiver computes a location from GPS alone, before a 北
斗 satellite was found by the receiver. It is a start-up effect. From
this histogram you can see that there are a fair number of locations
where 4 or 5, or even 6 北斗 satellites were in view. Not bad at all.
The third figure shows the
number of 北斗 satellites actually used in a location
computation. Satellite counts are lower here. This is simply caused by
the fact that even when a satellite is over the horizon (in view
according to the receiver) it's signal path may be obstructed by
buildings. You can see that the 北斗 system presently is not really a
very useful system yet. There are simply not enough satellites
available for users here in Europe.
The fourth figure shows the
histograms for the PRN numbers of the different satellites. There is
one geostationary satellite in view (the yellow bar), a fair number of
inclined geostationary satellites (the blue bars) and only three MEO
satellites (the green bars). This is somewhat surprising since there
should be more satellites in MEO available. This is probably due to
limitations in the Navspark receiver which actually has a built-in
upper limit for 北斗 PRNs.
The last
figure shows the actual receiver. The small boards at the top are the
actual Navspark receiver and an adapter board with SD card and a
battery charger. The screen is a simple Nokia screen. Quite simple
really. If i can solder this thing together, so can you.
According to the 北斗 agency the system will be global by 2020. Given how fast it has been built it might be a global system even sooner than that.