Every positioning signal tells part of the story. Sensor fusion is the practice of combining complementary measurements so that the strengths of one source cover the weaknesses of another.
What each source contributes
- GNSS provides a global reference outdoors. Its usefulness drops indoors, underground and between dense structures, where satellite signals are weakened or obstructed.
- RTK GNSS is designed to improve outdoor position accuracy when suitable correction information and satellite conditions are available.
- Wi-Fi and Bluetooth provide useful radio information inside buildings, but depend on the radio environment and on up-to-date radio maps or deployed devices.
- Accelerometers and gyroscopes describe movement and rotation continuously, without any external signal — but small errors accumulate into drift over time.
- Magnetic sensing can contribute heading and environmental information, and is affected by local magnetic disturbances such as steel structures.
- Pressure sensing can help estimate vertical movement, such as a change of floor.
How fusion works
A fusion engine keeps a running estimate of position and motion. Motion sensors predict how that estimate changes from moment to moment; radio and satellite observations correct it when they are available. Techniques such as Kalman filtering weigh each measurement by how far it can be trusted, and map constraints — walls and corridors on an indoor map — rule out impossible movement.
Why it matters in practice
Fusion reduces dependence on any single signal source. When a person walks from a car park into a building, satellite observations fade, radio observations appear and motion sensing carries the estimate across the gap. The location picture can continue as the environment changes instead of starting over at every boundary.
KPT positioning systems combine available information rather than relying on one measurement alone. See how the layers fit together on the Technology page.