Navigating the uncharted: GNSS impossible

The world feels smaller than ever. Thanks to relentless innovation in aircraft design, much of the globe is now reachable within a flight or two from any major city. Behind this extraordinary connectivity lies an equally impressive evolution in aviation policy, regulation and navigation.

The Era of Conventional Navigation Aids

For most of the 20th century, aircraft navigation depended on analog radio beacons and ground based signals from systems such as:

• VOR's (Very high frequency Omnidirectional Beacons)

• NDBs (Non-directional beacons)

• DME (Distance Measuring equipment)

Picture of a VOR ground station. Source. Flyingmag.com

For decades these ground stations processed geodetic data and beamed radio signals to flight decks, safely guiding pilots along fixed routes, these systems matured to uncanny levels of precision, now enabling autonomous landings with CATIIIB landings in near zero visibility.

Demonstration of low visibility from a flight deck window. Source: METAR Group

For generations these beacons were the foundation to safe navigation. Policy and regulation grew around it which is ingrained in current training and created an extraordinarily high level of safety, however ground based navigation aids come at a cost, they require:

• Reliable and stable power supplies

• Regular inspection and calibration

• Significant amount of land free from obstruction

• All of the above come with high cost

As global air traffic surged, the traditional beacon to beacon structure begun to show its limits. Aircraft were constrained to flying along invisible highways drawn between fixed ground points.

Aircraft navigating using conventional navigation aids Source: METAR Group

Capacity was constrained by infrastructure, something more flexible was needed.

RNAV (Area Navigation): New highways in the sky.

The simple question was: How do we increase airspace capacity without building more physical beacons?

RNAV - Area Navigation was the answer!

As aircraft systems advanced and inertial navigation became widespread, aircraft could calculate their position relative to existing navigation aids by using combinations of radials and distances from beacons. Using this same theory new 'virtual' waypoints could be created as a point in space.

Aircraft could now navigate directly between these defined points rather than beacon to beacon, the result?

• More direct routes

• Reduced track miles

• Lower fuel costs

• Greater airspace efficiency

Conventional RNAV was a major step forward, but it still depended on the serviceability and maintenance of physical ground-based infrastructure.

The next step required us to look even further into the skies and beyond!

GNSS (Global Navigation Satellite Systems)

GNSS has been around for some time, but properly understanding and enhancing its capability is a fine balance between safety and the explosive growth in aviation.

Rather than referencing ground-based transmitters, aircraft could now determine their position using GPS satellite information with the data and position processing done by onboard GPS processors. No radials. No signal intercepts. Just guidance from above.

The shift unlocks some benefits:

• Navigation independent of ground infrastructure

• Navigational access to remote or power-disconnected airfields

• Rapid deployment of new procedures

• Reduced infrastructure costs for service providers

Across the UK and beyond, conventional navigation aids are steadily being retired and replaced with GNSS based equivalents. Click here to see the recent NATS Y Circular which references the changes.

GNSS isn't perfect - but its powerful!

Like all technology, GNSS has vulnerabilities.

Jamming and spoofing present a real challenge to aviation. These threats are shaping ongoing discussions around resilience and backups, a topic we are passionate about that will be explored further in a future blog. Focusing on the capability itself, GNSS has changed whats possible.

Precision in demanding environments

Not only are we able to use GNSS navigation to navigate aircraft in the cruise but for us at the METAR Group we are helping set up GNSS style approaches to help guide aircraft into remote, sometimes hostile environments, imagine being able to guide an aircraft through treacherous terrain in minimal visibility to a predefined location enabling its crew to focus on mission execution?

By defining GPS based waypoints and coding approach procedures with a unique language directly into aircraft navigation systems, complex approach paths can be designed around terrain, obstacles and mission or operational constraints.

Furthermore, with the introduction of RNP (Required Navigation Performance), aircraft systems continuously monitor its own navigational accuracy. If performance drops below a specific threshold, pilots are alerted adding another layer of safety and situational awareness.

At METAR Group, we've been involved in developing GNSS based procedures for remote airfields disconnected from power networks or lacking instrument procedures in challenging operational environments. These solutions don't just improve accessibility but allow crews to focus on mission execution whilst utilising in cockpit technology to navigate safely.

The Future: Performance, Not Infrastructure

The evolution of aviation navigation reflects a broader shift in aviation philosophy.

Taking what we have learnt to move ahead from infrastructure defined routes to performance defined airspace.

From physical beacons, to digital precision.

In our next blog, our Senior Data Analyst will dive deeper into the coding language behind these procedures and how RNAV and GNSS combine to create modern navigational solutions.