Monthly Archives: March 2016

Constellation Considerations for New GNSS Purchase

A long-time customer asks this question:

We talked a few months ago and you mentioned I think on new years day you used Galileo briefly and was cool. Have you noticed it working lately or any other constellations coming up soon? Whenever the new systems actually start working to be game changer I definitely want to upgrade my older units.

Actually I said that GLONASS was unavailable and I took a look a Galileo and was surprised that there were 7 satellites in my solution.

I want to answer this question explicitly for customers in the USA: if you purchase a new RTK system, you want it to track GPS + GLONASS + Galileo + BeiDou satellites. (If you are in Africa, Asia, Russia your receiver should track and use QZSS too.) You need to be very, very careful here.

  1. There is a major brand of equipment that advertises that it tracks ALL FOUR constellations, but the fine print discloses that only three constellations can be tracked simultaneously AND to make it worse, switching requires a major activation code nightmare.
  2. There are other brands that may track all four constellations, but only basic GPS and GLONASS are activated when you purchase the equipment. Turning on L2C, L5, Galileo, BeiDou costs extra and the cost is significant.

Let me explicitly list the signals that EVERY modern receiver should track:

GPS L1-C/A, L2E, L2C, L5
Galileo E1, E5-A, E5-B, E5-AltBOC
BeiDou B1, B2

Currently QZSS won’t buy you much in the USA, however since it is available at no cost on many receivers you should demand that it can be tracked because it might be valuable in the future.

Now, you may wonder why Galileo is important today (26 March 2016). This is the Galileo satellite availability for the reference station that operates at our office in Salt Lake City:


I drew a purple line at one of the places where Galileo adds 7 (SEVEN!) extra SV’s to the solution. Now you may argue that most networks don’t provide GAL corrections. This is true today, but remember that I am selling matched Base Rover pairs that track ALL of the signals for $12,500 for a pair. If you are working under canopy, then Galileo may be a game maker and it would certainly be worth setting up your own base (using the network) so that you can have 7 extra SV’s (SV is the abbreviation for Satellite Vehicle).

Here is a similar plot for BeiDou SV’s:


BeiDou only adds 4 SV’s, however China is going to launch many more BDU SV’s Real-Soon-Now. And when they do, you are going to wish like heck that you can track them.

The Holy Grail of RTK GNSS is accurate fixed solutions under heavy canopy. There are two primary contributors to this goal:

  1. Super-duper RTK algorithms. And yes, every year every manufacturer makes huge strides in their processing every year.
  2. More Satellites and more signals (like L5).

Some places have a lot of SV’s available today. In Asia, there are often over 40 SV’s available. Some places, not so many.

The reality is you should plan to replace your GNSS receivers EVERY FIVE YEARS so that you can take advantage of new features, hardware and firmware. In the next two years there are going to be a lot more BDU and GAL SV’s.

Let me be clear. You are stupid if you don’t purchase equipment that tracks GPS + GLONASS + Galileo and BeiDou simultaneously with the signals listed above.

Ignore equipment that claims tracking, but not simultaneous tracking. Ignore equipment that requires purchasing options to enable L2C, L5 and GLONASS L3. If your vendor is trying to pull tricks like this, they are dishonest and you should not do business with them. You are purchasing new equipment. It should be complete out of the box!






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