Indoor geolocation in airports, how does it work ?

Indicating a precise position inside a building. Is this a dream?
Well not anymore. New technologies that do inside what GPS does outside have developed. They allow a cell phone user to navigate inside an airport exactly as he would do in a street.
As GPS signals are not available inside buildings, it is necessary to install an infrastructure that will play a similar role. This infrastructure can be made of Wi-Fi or Bluetooth emitters.
The geolocation system uses Bluetooth or Wi-Fi emitters to determine the position by calculating the distance from each emitter. This technique is called "triangulation" because it refers to the fact that calculating a position on a map requires to calculate distance from 3 known points.
A very important point to notice is that these technologies allow to identify the right level in the building. For example, emitters at the departure level are not the same as the ones at arrival level.
Accuracy depends on several factors such as emitters density (number of emitters in the area, the more emitters the higher the accuracy), height at which emitters are placed, speed of calculation, algorithms... but a good estimate is to say that it ranges from 3m to 10m. Typical density for Bluetooth emitters is around 1 emitter per 100 square meters. For Wi-Fi, density is around 1 emitter for 500 to 1000 square meters.
As emitters’ price and ease of installation are different, choice between Bluetooth and Wi-Fi is really location specific. No generic rule can apply.
Setting up such a system requires to calibrate the map. This means teaching to the system where the emitters are. Instead of doing this theoretically by indicating emitters’ position on the map it is usually quicker to take a series of measurement on site and indicate to the system what the location is.

The addressable market for such solutions is the portion of users that have a phone on which a map can be displayed, and that has Wi-Fi or Bluetooth. It is considered that approximately 30% of the global population in western countries has a phone compatible with these technologies. Among passenger, it is likely that the proportion is around 70%.