Editorial Advisory Board PNT Q&A: GNSS diminishing returns?

As the number of GNSS constellations and satellites in orbit continues to grow,
will we reach the point of diminishing returns?

Ellen Hall

“More satellites equal more data, and redundant constellation systems — through GNSS interoperability — can give us more robust PNT, as restated in the January Memorandum on Space Policy Directive 7. That said, there are always diminishing returns. Treaties place liability on the launching country if something goes wrong, but with tens of thousands of small satellites expected to be launched over the next decade, it will be getting increasingly crowded. Concerns are growing about the necessity of increased maneuvers to keep these satellites from a chain reaction of collisions, which ultimately could cause debris to fall to inhabited areas of Earth.”
— Ellen Hall / Spirent Federal Systems

Jean-Marie Sleewaegen

“With already more than 130 GNSS satellites in orbit, the benefit of new satellites decreases while the risk of satellites interfering with each other increases. However, this is only considering GNSS as we know it, in the MEO orbit (altitude about 22,000 km). The future of GNSS may well be closer to Earth, in the LEO orbit (<1,000 km), with well-known benefits in terms of convergence time and resilience to jamming. Sooner than later, we can expect constellations of hundreds or thousands of LEO satellites carrying a GNSS-like payload supporting PNT services. No worries, there is still growth potential!”
— Jean-Marie Sleewaegen / Septentrio

Stuart Riley

“With the current four GNSS constellations and a typical survey elevation mask of 10˚in North America, we average around 30 visible satellites. Far more are visible in Asia with the addition of the regional systems. In an area with a clear view of the sky, this provides more than enough satellites for precision centimeter positioning. However, most professional GNSS users do not have the luxury of operating exclusively in open areas with ideal conditions. Accessing many satellites across multiple constellations increases the probability of receiving sufficient satellites that produce high-quality measurements in obstructed areas. As the constellations expand, we observe improvement in precision position availability in these locations. The large number of satellites, coupled with independence across the four systems, improves system integrity and continuity while also helping to reduce the converge time in PPP solutions.”
— Stuart Riley / Trimble

Bernard Gruber

“In a utopian vision of navigation, data gluttons and like-users of GNSS would say that there will never be enough! If capabilities remained static, then yes, I believe we would reach the point of diminishing returns. I would offer that innovation and competition will continue to drive capability improvements via power, signal quality, coverage, integrity and clock/timing accuracy. These innovations, coupled with user equipment flexibility utilizing signals from space, will drive an ever-maturing market balance and increasing return.”
— Bernard Gruber / Northrop Grumman