Autonomous Inertial Navigation

Imagine getting lost in a maze-like city, deep inside a high-rise building or navigating in the depths of a mine where GPS signals simply won't penetrate. Traditional navigation tools fail you, but this is where independent inertial navigation comes to the rescue. This technology, known in English as Pedestrian Dead Reckoning (PDR), makes it possible to estimate your position without relying on external signals. Let's explore what autonomous inertial navigation is and its exciting applications beyond just guiding us through shopping centres.

What is autonomous inertial navigation?

Basically, the independent inertial navigation a technique to estimate your current position based on your previous location, direction of travel and distance travelled. Unlike GPS, which relies on external satellite signals, this method is an autonomous navigation system, making it invaluable in GPS-free environments. It relies primarily on sensors such as accelerometers, gyroscopes and magnetometers - all commonly found in modern smartphones.

How does autonomous inertial navigation work?

Let's break down the basic components of the system and how they interact to track your movement:

Your smartphone has an incredibly sensitive accelerometer. This sensor is fine-tuned to detect subtle accelerations and decelerations in your body with every step.
Algorithms analyse the patterns in the accelerometer data. They identify the distinct peaks and troughs that correspond to your rhythmic up-and-down movement while walking.
Each detected step is like a beat in a rhythm, providing a crucial reference point for calculating the distance travelled.

Calculating step length: putting distances on the map

Knowing that you have taken a step is only part of the equation. The system must also determine how far you move with each step. Here are the main methods:

Average step length: The simplest approach is based on a general average stride length. This works, but tends to be the least accurate as everyone's walking patterns are slightly different.
Personalised step length: You can improve accuracy by taking the time to measure your own step length and entering that value. A simple method is to walk a known distance (e.g. 10 metres), count your steps and divide the distance by your number of steps.
Dynamic algorithms: Precision at the highest level: The most advanced systems continuously analyse your movement data. These algorithms adapt in real time to changes in your walking pattern. This is extremely valuable as your stride length can naturally vary depending on speed, terrain or if you are carrying a heavy backpack.

Staying on course: Magnetometer and direction

Your phone's magnetometer works like a digital compass. It senses the Earth's magnetic field and determines which way you are facing. This directional data is crucial for independent inertial navigation and ensures that the system knows whether you are travelling north, south, east, west or any direction in between. At each step, the system has three key tasks:

Step detection: It knows that you have moved.
Step length: It has an estimate of how far you have travelled.
Direction of travel: It knows which way you are moving.

By combining these data points, the system calculates the change in your position. Think of it as drawing a small arrow on a map - the step is the starting point, the step length determines the length of the arrow and the direction determines its angle. By constantly repeating this calculation for each step, the system maps your path and updates your location on the map.

Applications of autonomous inertial navigation: Military, navigation and underwater vehicles

While the technology has clear benefits for everyday navigation (e.g. shopping centres and pedometers), its real potential lies in specialised applications:

Navigation for soldiers on foot: To integrate independent inertial navigation in soldiers' equipment allows them to track their position with precision, even in GPS-free environments such as urban areas or dense forests. This significantly improves situational awareness and mission planning.
Monitoring of targets: With system-equipped units, soldiers can track the movement of both friendly and enemy forces, even when they disappear behind cover or move indoors. This real-time data improves coordination and combat situational awareness.
Precision in GPS-free environments: The technology becomes crucial when GPS signals are weakened or non-existent. In complex marine scenarios or areas with electronic jamming, it enables independent inertial navigation in combination with inertial navigation systems, reliable position data for ships and other large craft, enabling safe navigation.
Autonomous missions: Underwater vehicles, such as autonomous underwater vehicles (AUVs) and unmanned underwater vehicles (UUVs), cannot rely on GPS underwater. Algorithms similar to independent inertial navigationbut adapted to vessel movements, together with specialised sensors such as depth gauges and sonar, allow these vessels to navigate autonomously.

The future of autonomous inertial navigation

Autonomous inertial navigation is an exciting area with the potential to revolutionise the way we navigate. With advances in sensor technology and algorithms, the technology is becoming even more accurate and robust - whether indoors, outdoors, underground or underwater! It acts as a powerful partner to GPS, filling the gaps where satellite-based systems fail.

Are you fascinated by the latest navigation technology? Explore the latest research advances and see how independent inertial navigation changing military operations and underwater exploration!

This is a translated article from our partner NIBP Sensor.

Autonomous Inertial Navigation: Navigating when GPS is not enough