Dead Reckoning
Dead reckoning is a positioning method that estimates where a vehicle has moved after a confirmed satellite position becomes unavailable. Starting from the last reliable location, the system calculates subsequent positions using elapsed time, travel speed, direction, and distance. It helps maintain location continuity inside tunnels, underground loading docks, covered depots, urban canyons, and other areas where GNSS signals are blocked or reflected.
Vehicle systems may obtain movement data from wheel-speed sensors, the odometer, steering inputs, accelerometers, and gyroscopes. These measurements are combined to estimate changes in motion and heading until a dependable satellite fix returns. The platform can then reconcile the estimated path with the newly confirmed position. Because every sensor contains small errors, accuracy gradually deteriorates as the outage continues. Wheel slip, sharp turns, incorrect calibration, vibration, and sensor bias can increase this drift.
For fleet operations, dead reckoning can prevent vehicles from appearing frozen or jumping abruptly across the map during short GNSS interruptions. More consistent positioning reliably supports tunnel navigation, geofence events, arrival detection, route histories, and dispatch visibility. However, estimated locations should be identified clearly rather than presented as satellite-confirmed coordinates. Buyers should assess supported sensors, expected accuracy, maximum useful outage duration, calibration requirements, and how the platform corrects accumulated error when GNSS reception resumes.
Common questions
Quick answers related to Dead Reckoning.
How does dead reckoning calculate vehicle position?
Dead reckoning starts with the vehicle’s last reliable position and estimates subsequent movement from speed, direction, distance, and elapsed time. Modern systems may combine wheel-speed, steering, accelerometer, and gyroscope data to calculate positions until a trustworthy satellite fix becomes available again.
What is the difference between GNSS and dead reckoning?
GNSS calculates position from satellite signals, while dead reckoning estimates movement without continuously receiving those signals. GNSS provides an external position reference. Dead reckoning uses the last confirmed location and onboard motion data to bridge a temporary gap in satellite coverage.
Why does dead-reckoning accuracy decrease over time?
Dead reckoning becomes less accurate over time because small measurement errors accumulate with every calculation. Sensor bias, wheel slip, vibration, turns, speed errors, and poor calibration can increase drift. A fresh GNSS fix is normally used to correct the estimated position.
Does dead reckoning provide accurate tracking inside tunnels?
Dead reckoning can maintain an estimated route through tunnels when satellite reception disappears, supporting smoother navigation and fleet visibility. Its accuracy depends on sensor quality, calibration, vehicle movement, and outage duration, so the resulting position should not be treated as perfectly precise.
What should fleets evaluate in a dead-reckoning system?
Fleets should evaluate expected accuracy, supported vehicle sensors, installation and calibration needs, outage duration, map matching, and recovery after GNSS returns. They should also confirm whether estimated positions are labelled and how dead-reckoned data affects geofences, alerts, reports, and integrations.
