Modern smartphones have multiple sensors, which can be combined to get a more precise indoor positioning result. Using vertical sensor fusion has one big advantage: combining various sensors results in a more homogenous and more reliable outcome than using just one type.
Most smartphones have the following sensors installed:
- Barometer: measures barometric pressure and thus can provide information about the current height – for example the floor the smartphone is on.
- Acceleration sensor: measures force shift on the axes X, Y and Z when the phone is being moved. Helps saving energy.
- Bluetooth: Bluetooth is a radio standard for data transfer at short range. It can be used for positioning (Bluetooth 4 and 5). The signal can be impaired by shielding objects, for example the human body.
- GPS: If there is visual contact with GPS satellites, the smartphone can determine its position.
- Gyroscope: The gyroscope detects if the orientation of the smartphone is vertical or horizontal.
- Magnetometer: This sensor measures the strength of the earth’s magnetic field and its direction according to 3 axes. This sensor is not always suitable for indoor positioning, because it is being impaired by magnetic fields caused by electric cables etc.
- Mobile phone antenna: Via GSM, 3G/4G the position of a smartphone can be detected – however the positioning is not very precise.
- NFC: NFC is a radio standard with a maximum range of 10 centimeters. It is used for access control and contactless payment.
- Camera: Most smartphones have a camera on the front and one on the back. They can receive VLC (visible light communication) signals and can be used for virtual reality applications.
- Wi-Fi: Wi-Fi can be used for positioning with an accuracy of 5-15 meters. iOS devices are not able to determine their position client-based with the help of Wi-Fi. Wi-Fi signals can be impaired by objects, such as the human body.
