Page 35 - Demo

33solve this problem, Prof. Chen and his team proposed a new method that corrects GNSS measurements directly based on a satellite%u2019s ID. This enables smartphones to achieve horizontal accuracy within two metres. However, building reference stations for local DGNSS corrections is not only expensive, but also extremely difficult on a global scale. To address this, the team developed a novel DGNSS platform that uses public precise corrections %u2013 highly accurate positioning data that is freely available online to the public, thus eliminating the need for physical reference stations. This is a reliable and affordable way to achieve accurate satellite positioning.Uniquely urban: multipath mitigation platformTall buildings in city centres can give rise to the multipath problem. %u201cThe multipath problem arises when not all received signals travel directly from satellites,%u201d explains Prof. Chen. %u201cSignals that are reflected or diffracted by a local structure travel a longer path, leading to incorrect measurements. The problem is how to distinguish direct signals from bounced signals.%u201d To tackle this challenge, the team cross-referenced satellite positions with location data from inertial measurement unit (IMU) sensors on smartphones, as well as 3D building models that document the shape and height of each building in a city. This helped them identify which satellites could be seen directly from a specific spot, and which signals were reflected or diffracted. Experiments conducted in Wan Chai showed that this method could improve smartphone positioning accuracy from 30 metres to less than 10 metres.Ever ready: Bluetooth Low Energy (BLE) beaconsAnother way to improve positioning accuracy is to use Bluetooth Low Energy (BLE) beacons. These beacons continuously broadcast unique signals that smartphones can detect. When a smartphone is within the range of a beacon, the accurate position of the beacon can help improve satellite positioning. BLE beacons can also detect in which direction a device is moving as it moves from within the range of one beacon to within the range of a neighbouring beacon. ON THE BUTTON