What is dead reckoning?
The term “dead reckoning” has been used in navigation for centuries, referring to deriving a position based on the direction and speed of travel from a starting point. Today, this is also known as inertial sensing, and in practice, it looks very different from the original applications of mariners or explorers. However, the foundational logic of dead reckoning remains relatively the same as it has been for hundreds of years.
For example, modern inertial sensors can be embedded into a car’s tires along with rotary encoders to measure how many accelerations and rotations occur, which you can then use to determine how fast the vehicle is going and in what direction. Using this information, the navigation system can calculate the car’s location based on where and when it started moving.
Inertial sensing & dual-band GNSS
GNSS technology is largely considered the gold standard for positioning, especially given the rise of multi-band solutions. In reality, the gold standard is a tech stack of dead reckoning and GNSS technology that provides precise positioning from satellites and complements that data with inertial sensing to bridge gaps caused by signal errors or unavailability and augment navigation systems.
Multi or dual-band solutions have greatly improved GNSS positioning accuracy and have become more accessible in the past few years. There are many causes of GNSS positioning errors – more on that here – but multipath errors occur when two signals travel different lengths from the transmitter to the receiver.
Dual-band solutions can better measure these discrepancies by tracking signal bands from multiple frequencies and derive more precise positioning. However, there are still many situations in which GNSS is insufficient, and dead reckoning is needed to fill in the gaps and provide additional context for the most accurate positioning.
5 reasons why you need dead reckoning
Despite continued innovation in the industry, sometimes GNSS just doesn’t cut it. Here are the top five scenarios when inertial sensing is needed to provide precise positioning to complement GNSS.
1. Deriving positioning information during signal outages
In these instances, inertial sensors provide highly accurate positioning information based on speed, direction, and altitude. Remember, though, there are a few different ways to implement dead reckoning in this situation. We wrote about them here so you can choose the method that best suits your particular use case.
2. Aiding GNSS position estimation to improve data quality
Similarly, dead reckoning can augment positioning calculations when GNSS signal quality is poor. The same factors that can completely obstruct signals can also severely degrade their quality, and sometimes, even other sources of RF interference (think nearby cell towers or modems) can play a role.
Although signals are not completely obstructed, making them technically usable for deriving location, this decreased quality can greatly impact positioning calculations. At these times, you can use data collected by inertial sensors to estimate position better.
3. Collecting data
An additional benefit of inertial sensors is their ability to continuously capture data specific to the vehicle or piece of hardware it is connected to. While it is possible to observe positioning history from GNSS and RTK data, dead reckoning solutions collect data about the unique movement of the object they are attached to, including speed, direction, altitude, and more.
While this data is primarily captured to fuel positioning calculations when GNSS fails, it provides the added benefit of showing movement history you cannot derive from GNSS signal data alone. You can use these insights to track driving behavior, autonomous vehicle (AV) performance, and similar trends.
4. Improving speed and affordability
GNSS solutions are computationally expensive, usually occurring at 1 Hz or 10 Hz. Inertial measurements can occur at 100 Hz or higher and can dead reckon between GNSS updates to provide positioning data for geotagging cameras and complementing LiDAR or radar data.
These time and cost savings help scale positioning across geographies, use cases, and more.
5. Providing protection against spoofing or signal jamming
Last – but certainly not least – inertial sensors provide foundational positioning information that can be relied on when GNSS signals are compromised. Unfortunately, today’s GNSS users must contend with the possibility of hackers jamming or spoofing their receivers.
While this is relatively rare for consumer positioning, large-scale GNSS commercial or intelligence applications must maintain a backup to avoid making critical decisions based on inaccurate information.
That’s where dead reckoning comes in; inertial sensors provide reliable positioning data free from outside influence to enhance the resilience of location-based technology.
Get started with high-precision dead reckoning
At Point One, we specialize in providing the most precise, affordable, and accessible positioning technology to power location-based applications worldwide. Our inertial navigation offerings implement our leading sensor fusion algorithms, enabling high-precision positioning for a wide variety of use cases.
Atlas and FusionEngine make it possible to build with robust position and navigation information easily, and include this information into a product or system with minimal engineering effort. You can learn more about the technical specs of our inertial navigation system here, including details about our tightly-coupled sensor fusion, centimeter-level accuracy, and open sky vs. urban performance metrics.