11 Mar 2022

No, dual band GPS does not replace dead reckoning

Dual-band GPS optimizes positioning accuracy. Dead reckoning receivers go a few steps further.

Dead reckoning solutions boost GPS performance in urban environments

It’s somewhat ironic that GPS-based solutions struggle most where they are most used: in urban environments. At best, deep urban canyons, underpasses, tunnels, built canopies, and indoor parking briefly deteriorate global navigation satellite system (GNSS) signal quality and position accuracy. At worst, they interrupt service altogether, potentially handicapping businesses that depend on accurate positioning to track their vehicle fleets, streamline operations and maintenance, and manage billing. 

There are a variety of solutions that help reduce outliers to deliver more stable performance – under the right circumstances. GNSS receivers that track multiple satellite constellations, for example, increase the number of satellites that are within line of sight at any given time, even when only a small portion of the sky is unobstructed. While this reduces the likelihood of having too few signals to calculate a position estimate, it does nothing to help manage multipath effects caused when GNSS signals bounce off facades before reaching the receiver.

Dual band GNSS technology aims to mitigate these multipath effects by tracking signals in frequency bands that each take different paths to reach the receiver. But while multiband positioning solutions currently on the market could potentially improve positioning performance in urban environments, not all customers and end customers report perceiving these benefits, leaving many of the urban positioning challenges mentioned unaddressed. 

The unique benefits of inertial sensing

Dead reckoning solutions uniquely overcome some of these challenges, delivering improved positioning accuracy in typical urban environments by drawing on inertial sensors embedded in the GNSS receiver module as well as, when available, additional data from the vehicle’s wheel tick sensor. They do so by combining inertial sensor data and a dynamic model accounting for all possible movements of the vehicle to eliminate poor position estimates caused by multipath effects or poor signal environments. 

But dead reckoning goes a few steps further than that. Here are four more ways that dead reckoning adds value to vehicle fleet management solutions. 

Bridging signal outages

Weak GNSS signals fail to penetrate through even thin opaque structures. As a result, indoor parking garages, tunnels, and even underpasses typically completely interrupt GNSS service. Even when GNSS signals are absent, IMU-based positioning continues, offering a complementary source of position information that can bridge gaps in satellite signal availability. 

Added resilience against jamming and spoofing

In addition to enhancing coverage of the positioning service, the inertial sensors that dead reckoning solutions draw on offer increased resilience against two of the most common methods of tampering with GNSS receivers - jamming and spoofing. Hackers can, for example, disrupt their operation by jamming them with loud radio-frequency noise. 

Alternatively, they can trick receivers into reporting false positions by spoofing them with fake GNSS signals. In these cases, inertial sensors offer a valuable complementary data source to maintain position service when signals are jammed or detect discrepancies between the GNSS and IMU output when signals are spoofed.  

Short-term drops in GNSS signal quality

Whether due to RF interference caused by nearby cellular modems, or physical obstructions such as trees and buildings, GNSS receivers often have to work with sub-optimal satellite signal quality. In these cases, inertial sensor-based positioning can be used to constrain the GNSS receiver’s position estimate to ensure that temporarily poor signal quality does not translate directly to inaccurately reported positions.  

Valuable data for vehicle insurance

One step removed from the positioning function itself, dead reckoning solutions can provide valuable raw data that fleet managers and vehicle insurers can tap into to gain previously hard-to-access information. This ranges from using the wake-on-motion functionality for theft detection or to detect minor collisions on parked vehicles to help insurance companies reduce expenses associated with unjustified claims. 

Additionally, it can be used to assess driver behavior, rewarding companies with cautious drivers with reduced insurance rates while charging more from those with reckless driving habits.   

Complementary, not competing, solutions

By now it should be clear comparing dual band and dead reckoning solutions is like comparing apples and oranges. Today’s dual band positioning solutions, while easy to implement (all they require is a dual band GNSS receiver and antenna), bring marginal improvements in positioning performance in urban areas under heavy multipath conditions. Dead reckoning technology goes one step further, improving accuracy in urban areas, as well as extending positioning service beyond the reach of GNSS signals, increasing resilience against jamming and spoofing, and offering new functionalities for fleet management and vehicle insurance companies. 

Ultimately, the trend will be towards increasingly sophisticated solutions that enhance positioning performance and extend it to an ever-growing set of environments. In the long run, multiband GNSS and dead reckoning will no doubt merge to further step up the reliability of GNSS positioning in our cities. 

In the meantime, learn more about the u-blox NEO-M9V receiver, our latest u-blox GNSS module offering both untethered and automotive dead reckoning (UDR and ADR), specifically designed with fleet management and micromobility applications in mind. Test the module’s functionality and push it to its limits with the EVK-M9DR, its dedicated evaluation kit. For questions, technical support, and further information, be sure to reach out to your nearest sales representative. We look forward to hearing from you! 

Mathias Vetter

Principal Product Manager, Consumer and Industrial Tracking

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