In order to compute the most accurate estimate, Situm fuses all the available sensor information that modern smartphones provide. Not all sensors are required: Situm is always able to make the most of the available information.
- Required:
- Wifi and/or BLE.
- Accelerometer.
- Recommended:
- GPS.
- Gyroscope.
- Magnetometer.
- Barometer.
Click here for more information on smartphone & sensor compatibility.
WiFi
Almost every building in the world has a WiFi network installed. The wireless signals that WiFi Access Points (WiFi APs) emit can be received by all Android smartphones to provide accurate indoor positioning. After the calibration step is performed, Situm builds a WiFi signal map based on users' geolocations will be computed.
BLE (Bluetooth Low Energy)
Similar to WiFi APs, BLE beacons emit wireless signals (Bluetooth) that can be received by all modern smartphones (both Android and iOS). These signals can be captured during the calibration step and used to provide an accurate indoor location.
BLE & WiFi signals are totally complementary: Situm will work with either of them, or with both at the same time. In fact, if your app is only for Android smartphones, chances are that you will not need to install any BLE beacon.
Anyway, BLE beacons are inexpensive and easy to install & maintain: this is why they are becoming increasingly more popular and many buildings already have them available.
Accelerometer
This sensor captures the acceleration that the smartphone experiences. At rest, the accelerometer is only subject to the Earths' gravity, but when the smartphone moves there will be other forces at play. These forces can be meassured in order to estimate how the user moves around the environment.
GPS
This sensor provides an absolute location (latitude, longitude) within the whole Earth. Sadly, it is not accurate in indoor environments, but the information that it provides can be used outdoors to improve the geolocation estimation provided by Situm, or to provide a proper geolocation anywhere in the world, even if Situm technology is not available.
Gyroscope
This sensor measures the angular velocity of the smartphone: that is, the rate at which the smartphone turns. The gyroscope can be used to update the device's orientation.
Magnetometer
The magnetometer is the sensor that meassures the direction and strenght of the magnetic fields surrounding your smartphone. Typically, based on the magnetometer data the Earth's magnetic field can be isolated, providing the device's orientation with respect to the North. In this case, we typically call the magnetometer a compass.
Compass information can be used to determine the device's orientation, which may play a great deal in enhancing the location accuracy. Raw magnetometer information can also be used to meassure the building's magnetic fields (interferences caused by objects & currents) in order to enhance the location accuracy.
Barometer
The barometer is a sensor that meassures the air pressure. Since the air pressure depends on the altitude, the barometer can help in estimating the floor where the user is in.