calculate distance very accurately

[guyulmaz]

Hello,

is it somehow possible to calculate the distance of a BLE enabled and advertising periodially cell phone to a turnstyle gate.

There are for example 10 turnstyle gates. We want to know exactly in front of at which turnstyle the cell phone is.

Is it possible?

[AmbystomaLabs]

You can only use BLE to approximate distance. This is done by using the RSSI info to calculate the distance to the transmitter using an RF propagation model and the receivers reference sensitivity. As you will expect this can have a lot of fluctuation in the measurement due to the local environment. When very near to a BLE transmitter (under 2 meters) this can be accurate to a meter or so.  When farther than 10 meters from a transmitter the position info can be off by many meters. A 4dBm ble device has a maximum range of about 20 to 25 meters with most cell phones.

A cell phone comes up with accurate position info by using assisted GPS receivers (or similar such as GLONASS) to calculate a devices position by using signals received from orbiting satellites.