GNSS: In Pole Position

GNSS: In Pole Position


Less than 50 years ago, the concept of satellite positioning didn”t exist. Today, global navigation satellite systems have become inextricably intertwined with national security and infrastructure, international relations and our daily lives. Here’s a look at the route that got us here, and some of the obstacles and solutions on the road ahead, including the huge potential of integrating GNSS with other technologies — both old and new.

Last month saw the 55th anniversary of the Sputnik-1 launch, a pivotal moment in the genesis of GNSS and the space race. The scientists’ decision to listen out for its signals was, in effect, the GNSS universe’s equivalent of the Big Bang; it set GNSS technology in motion and its reach hasn’t stopped expanding since.

The world’s first global navigation satellite system was TRANSIT, designed and built for the US Navy — launched in 1959 and declared fully operational five years later. By the time TRANSIT reached retirement, almost 30 years later, the expansion of the GNSS universe was well underway. Its now-silent satellites shared the skies with GLONASS, Russia”s GNSS, and its own successor, GPS.

While GPS”s civilian signal had been available for many years, it had also been subject to ”selective availability”, a function that intentionally introduced time errors, reducing accuracy in the interest of preserving national security. While methods existed (such as differential GPS) to mitigate its effects, ”selective availability” generally cut accuracy from about 10 or 20 metre to almost 100 metre. Crucially, for popular adoption in road transport applications, that”s the difference between being on the 34th Street and 35th Street in New York City!

When US President Bill Clinton deactivated ”selective availability” on May 1 2000, the move”s intention (as stated in the White House”s own fact sheet), was to: “…accelerate [GPS”s] acceptance and use by businesses, governments, and private individuals in the US and around the world that will enjoy increases in productivity, efficiency, safety, scientific knowledge and quality of life.”

Over the last 10 years, and largely due to this decision, civil and commercial applications of GNSS positioning have indeed proliferated — as well as the systems delivering them.

As we travel further into the age of GNSS and as satellite positioning finds applications in an increasing range of sectors and industries, we are constantly learning — not only to make better use of the technology itself, but to deploy it alongside and integrate it with other technologies, to meet newer challenges. To see how, let”s examine current developments in several key industries.

The road vehicle is still, for many GNSS users, the natural home of satellite positioning. But today”s challenges are quite different from those we were looking to solve at the turn of the century. Having answered the problem of how we get to where we”re going, we are looking to GNSS to help us answer another problem, one that”s arguably even more crucial — how we get all of us there safely and sustainably. In the interest of sustainability, increasing demand for road use can no longer be countered with the construction of more, or wider, highways. (And, given the current global economic situation, it is not, in many instances, an attractive option financially.)

Simply increasing the physical size of our infrastructure would also do little to enhance safety. According to the World Health Organization”s Global Status Report for Road Safety 2009, approximately 1.3 million people die each year on the world”s roads, with (as more developing countries take to cars) road deaths estimated to be the fifth biggest cause of casualty by 2030.


GNSS positioning, when combined with other technologies, both old and new, has the potential not only to meet these challenges, but also to change our whole experience of road travel. With increased wireless radio connectivity — either between cars, or between cars and smart infrastructure — there is the possibility of intelligent speed control and information about traffic conditions or hazards ahead being transmitted to in-car displays, enhancing journey efficiency while improving safety.

Roughly 90 per cent of the accidents are caused by human error, however, and it is easy to see why some believe enhanced in-car warnings and automated security features will ultimately prove insufficient — that the real solution is to remove the capacity for human error altogether. With an array of sensors from laser distancing to radar, we are already seeing the first self-driving cars on our roads. Smarter cars offer not only the opportunity to make more efficient use of existing infrastructure, but also help us to plan acceleration based on the road ahead, reduce the need for braking (eg. at traffic signals), slipstream to save fuel. The realisation of ever more automated driving will, of course, depend on establishment and adoption of widespread standards, as well as the reliability and security of the systems they govern.

A train cabin may not be the first place where one would expect a GNSS receiver, but the potential benefits of incorporating GNSS technology into rolling stock are wide-ranging — from reduced infrastructure costs and more efficient operation, to enhanced passenger information and safety.

Potential railway-based applications of GNSS include positive train control and in-cab signaling, automatic door operation, on-train monitoring and recording, train and infrastructure protection and better information for rail users.

Then why GNSS is not there in all our trains? The key obstacle to bringing the benefits of GNSS to railways has always been the difficulty of guaranteeing positioning integrity (the reliability of the fix) and accuracy. This guarantee is clearly vital in applications where safety of life is at stake and the railway landscape, with its bridges, tunnels and cuttings, is particularly challenging for GNSS receivers, which need a clear line of sight to at least four satellites to establish a full positional fix.

As we move further into the age of multiple GNSS, however, the power of this obstacle is diminishing. Multi- GNSS receivers (which can process signals from more than one GNSS), naturally have access to more satellites, more of the time — meaning enhanced accuracy and availability, even in a railway”s often demanding environment.

The full promise of multi-GNSS seems likely to be realised through its combination with other technologies. Many of the world”s railways are already moving away from trackside infrastructure to onboard, in-cab, signalling. The European Rail Traffic Management System (an initiative to promote interoperability and safety across the EU), for example, relies on radio beacons inserted in the tracks at regular intervals, which relay information regarding the track ahead. By augmenting such a system with GNSS, there is the potential to reduce costs and increase reliability — as well as add some of the services outlined above.

Civil aviation
GNSS uptake in civil aviation is slower than one might expect — and again, one of the primary reasons is that lives are at stake and regulation is strong. Applications in other industries can take advantage of any GNSS signals available. To minimise the risk of interference, aviation applications must use signals transmitted on specific safety-of-life aeronautical radio navigation service (ARNS) bands. With the expansion of the world”s GNSS over the next few years, such signals are set to become more numerous and reliable.

GPS modernisation
The ongoing modernisation of GPS constellation, for example, includes the addition a new ARNS band signal L5. The US Government has stated L5 is to be, “reserved exclusively for aviation safety services … and features higher power, greater bandwidth, and an advanced signal design.” Greater availability and quality of aviation-grade signals can only help GNSS to take flight in civil aviation, removing one of the principal barriers to adoption. GNSS uptake in non-regulated industries, where signal integrity isn”t necessarily a matter of life and death, is currently proving much swifter.

One such industry is mining. Companies are already taking advantage of their relative regulatory freedom to create and operate fleets of self-driving, wirelessly connected trucks, as well as adding GNSS-aided automation to other key processes.

GNSS in action
At one of Vale”s opencast mines in the Amazon Rainforest, GNSS technology is not only employed to prevent the Brazilian company”s machines colliding with each other and with material stockpile, but to coordinate the movement of a mobile conveyor system, that crawls alongside the mining operation.

Indoor positioning
As we have taken the ability to know where we are, wherever we are, to our hearts, we have become increasingly reluctant to accept the idea that this ability has limits. Even multi- GNSS, as noted above, has limits — need for line of sight to the satellites. From in-store, in-museum or in-airport navigation to location-based marketing, new social and commercial location-aware applications demand accurate positioning in cities, indoors, and even underground. In this area, even more so than on our railways and roads, integration of GNSS with other technologies is providing many of the most compelling solutions.

Hybrid positioning
With smartphone adoption rate faster than any other consumer technology in history, there has been no lack of will to solve the indoor positioning challenge — and no dearth of solutions. The most promising include combining GNSS with Wi-Fi positioning (in which the location- aware device checks the landscape of the local Wi-Fi hotspots observed against a hotspot database) and augmenting GNSS with data from the inertial sensors commonly included in smartphones.

A smartphone”s accelerometers and other sensors naturally continue to function when GNSS signals are lost; by combining the last GNSSverified location with the information from these sensors, positioning accuracy and availability can be enhanced. The future of indoor positioning has a strong foundation: the recently formed ”indoor positioning alliance” In-Location. It is a group of 22 technology companies including Nokia, Sony and Samsung and has stated its commitment to collaborate on piloting new indoor positioning services, as well as promoting open interfaces and a standards-based approach.

Integration of GNSS with Wi-Fi, inertial sensors and other technologies is helping us to further extend its possibilities – and vice versa.

GNSS and its augmentations, however, also have the potential to support integration on a larger scale, to coordinate efficient, multi-modal journeys for goods and people. Less than 45 years from now it could be helping us find the fastest route from our house, across town in the safety of a self-driving car, straight through the labyrinthine train station, and onto a faster, more punctual train.

As the applications of GNSS expand, new challenges and obstacles will need to be dealt with. Ensuring positioning integrity and mitigating signal interference (whether natural or unnatural, accidental or malicious) will be essential for any application or service on which people rely. Today, there are very few quality standards for positioning integrity and receiver performance, a situation which will have to change as GNSS makes greater inroads into our lives and is relied upon by more of us, for more important things, every year.

But one thing is certain. The evolution of satellite positioning, and its applications, shows no signs of stopping. The next few years are set to prove very exciting indeed.