With upcoming GNSS systems that have better accuracy than GPS, could there be an GNSS based attitude indicator? Does maybe one already exist?

I could imagine having 4 sensors (front, aft, left wingtip, right wingtip) that then calculate the attitude.

  • 1
    $\begingroup$ Then what would be your backup in case of a GNSS/GPS outage? Part of the reason for Gyros is to have separate systems that can be cross-checked against each other. $\endgroup$
    – abelenky
    Sep 6, 2018 at 14:15
  • 1
    $\begingroup$ Even today, differential GPS accuracy is about 10cm, which is perfectly sufficient. The inaccuracy from wing bending is larger than that. $\endgroup$
    – Rainer P.
    Sep 6, 2018 at 15:29
  • $\begingroup$ Researchers at Stanford University had working prototypes 20 years ago. They worked, but not very practical or cost effective when compared to a solid state ADHRS which came about the same time. $\endgroup$
    – Gerry
    Sep 6, 2018 at 16:51
  • $\begingroup$ I visited a search and rescue cruiser some years ago that used three GPS receivers to calculate true heading at sea. $\endgroup$ Sep 6, 2018 at 20:49
  • $\begingroup$ Which GPS signal in particular are you referring too? All of them in general? $\endgroup$
    – jCisco
    Sep 10, 2018 at 1:20

4 Answers 4


I suppose you could but what benefit wound a GNSS based system offer over traditional gyroscopic and AHARS based attitudes systems while offering better redundancy against a system reliant on outside radio sources and risks with system outages, etc?


Part of the attitude determination on the ISS is done that way. The size of the space station makes for a larger measurement base then on an aircraft, but the idea is the same. Further, the ISS has an unobstructed view of the navigation satellites, and has lower rotation rates than one can expect on an aircraft, which makes it an easier problem. But, a quick search finds plenty of research for doing the same for aircraft.


There has been quite a bit of research on the topic and units have even been built. Ultimately it will trickle its way out there if the price of the unit drops below AHARS or Gyro equivalent units and its accuracy is equal or better than modern AI's. However you can get a good, small, drop in, AHARS style AI for fairly reasonable (considering the cost of avionics). The FAA seems to allow GNSS signals to supplement AHARS data I cant find a copy of TSO-C4c which outlines the certification limits for pitch and bank instruments but may shed more light on the topic.

Side note: to escape the mechanical dependence of gyros and if you want something different than what your run of the mill AHARS unit has, some of the newer high performance stuff uses a Ring Laser Gyro.


This isn't a direct answer to your question, but there has been research on a simpler gyro-free and GPS-free absolute attitude determination method based on a trio of 3-axis magnetometers and a trio of 3-axis accelerometers.

Very much like you imagine 4 GNSS sensors, they use a trio of 3-axis magnetometers -- each detecting the 3-axis direction of magnetic north.

They don't need to be at the extremities of the aircraft, just separated in space for sufficient magnetic and rotational accuracy.

The challenge to overcome lies with the fact that "the aircraft environment is very poor for the performance of the magnetometer, with large electromagnetic transients that cannot be calibrated out of the measurements". Their solution is to integrate a trio of accelerometers, and a time-filtered sampling method to reject transient magnetic readings.

They validated with limited test flights, but there is insufficient information to know how it might hold up to less-than-transient magnetic phenomena in the real world due to storms, static charges, etc.

The paper was published by Stanford in 2000...

A gyro-free quaternion-based attitude determination system suitable for implementation using low cost sensors

One future possibility might be to create an attitude detection system which incorporated all three methods (relative "digital" laser-gyro, motion extraction from a trio of accelerometers, vector extraction from a trio of 3-axis magnetometers, and absolute position extraction from four extremity mounted WAAS GNSS sensors), and used each to backup and reject spurious data from the others.

This would not only provide the least likelyhood of inaccurate attitude indication, but it would also provide extensive data on when there is divergence between the different methods.


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