Positioning technologies

In general, navigation and orientation systems can be divided into two main categories: indoor and outdoor. For outdoor, system like GPS is already widely adopted. For indoor, there is not yet a generic solution. But there are already many different solutions being developed. I'll briefly list the supporting technologies I found for indoor navigation. 



RFID

Radio Frequency Identification (RFID) tags can be used to determine object location within close range. It has been adopted in several other indoor navigation projects, both for human being and robots. 

The advantages of using RFID in locating are:

1, its accuracy due to very short operating range.

2, potential for auto mated date collection and object tracking.

3, relatively low cost to set up.

RFID tags could be divided as 2 kinds: active tags and passive tags. The active tag gives off radio signals themselves, and thus need to be powered. But it does have much bigger range, and the reader is relatively simpler and cheaper. The passive tag has no batteries, and is powered by the radiation sent by the reader. It is simpler in construction, and has longer lifespan. ( approx. 10 years   )

Bluetooth 

Bluetooth is a low cost, low power, short range radio technology originally developed as a cable replacement to connect devices such as mobile phones, headsets, PDAs and portable computers.  

To determine location using bluetooth, signal levels from at least 3 different base stations have to be measured, and triangulation is performed to calculate the position. Accuracy would be improved with more base station detected. 

WLAN

Similar to bluetooth, wireless LAN technology could be used in positioning too. Firstly, the position is determined by triangulation: the signal strength is used to calculate the distance to at least three WLAN access-points. Secondly, positioning can be achieved by using points with predefined respective signal strength (so called “fingerprint method”)[9].

This method utilizes the Wi-Fi infrastructure in the building, which makes it cost efficient. However, a drawback is its relatively low accuracy. (compared to bluetooth for example)