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GPS-denied navigation for fixed-wing UAVs: the special challenges

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Most GPS-denied navigation research and products started with multirotors that hover, fly slowly and stay close to the ground. Fixed-wing UAVs are different: they cannot stop, they fly faster and higher, and they cover long distances. Each of those differences changes which navigation methods work and how their errors behave.

What makes fixed-wing different

A fixed-wing aircraft generates lift by moving forward, so it is always in motion. That affects navigation in several ways:

  • Speed: the scene below changes faster, so visual methods must process images quickly and match features across larger motions.
  • Altitude: flying higher makes ground details smaller and depth harder to estimate, while giving a wider field of view.
  • Range: long, one-way flights rarely revisit the same place, so methods that rely on recognizing earlier locations have fewer chances to correct drift.
  • Manoeuvres: banked turns tilt the camera away from the ground and change the view rapidly.

Sensors that help on fixed-wing

Fixed-wing aircraft can use some sensors that multirotors use less:

  • Airspeed sensors (pitot tubes) measure speed through the air, which, combined with a wind estimate, helps constrain ground speed.
  • Barometric altimeters bound vertical error, especially important over long flights.
  • Downward or forward cameras support visual odometry and visual-inertial odometry (VIO).
  • A good IMU provides the high-rate backbone that every other source corrects.

Managing drift over long distances

On a long flight, relative methods such as inertial navigation and visual odometry accumulate error with distance. The practical goal is to keep that drift small for as long as possible and to bound it with whatever references are available. Wind is a particular challenge: it moves the aircraft relative to the ground in ways that airspeed alone does not reveal, so visual motion estimates are valuable for separating the two.

This is also why cost and weight matter on fixed-wing fleets: the navigation solution has to fit within the aircraft's payload and power budget while staying accurate over the whole flight.

GPS-denied navigation: methods compared →

Where IRA-2 fits

IRA-2 is iris's GPS-denied navigation kit for fixed-wing UAVs. It uses visual-inertial odometry (VIO), fusing camera and IMU data on board, and is designed to deliver accurate navigation without GPS at a fraction of the cost of traditional solutions. It is currently in development.

IRA-2: GPS-denied navigation kit for fixed-wing UAVs →

Frequently asked questions

Fixed-wing aircraft fly faster, higher and farther than multirotors and cannot hover. The scene changes quickly, ground details are smaller, and long one-way flights give fewer chances to correct accumulated error.

Yes, but it has to handle faster motion, higher altitude and banked turns. Combining the camera with an IMU, as in visual-inertial odometry, makes it more robust to these conditions.

Yes. Wind moves the aircraft relative to the ground in ways airspeed measurements alone do not show. Visual motion estimates help separate the aircraft's own motion from wind drift.