ULTRASOUND AND INFRARED
These technologies are especially suitable for positioning in rooms and enclosed spaces because they are dependent on signals that can be easily dim by walls. Senders and receivers can be LED, microphones, speakers and cameras.
Ultrasound
Ultrasound tracking is usually implemented using special microphones in each room. The items to be tracked have an ID Tag that contains a speaker.
The sound is stopped by the door, wall or window but not by other physical objects in the room like people or beds. This means that ultrasound is well-suited to locating items in a room.
Infrared
Infrared tracking functions in the same way. Any item to be tracked has an ID Tag that sends an infrared signal. The signals are received by one or several cameras fitted in the room. The more cameras installed, the greater the degree of accuracy. Infrared signals can be blocked by walls and by other physical items.
Continuous location of an item in a room may require several cameras aimed in different directions, e.g. on all four walls.
Ultrasound:
- Does not require a clear line of sight
- Long battery life
Infrared:
- No interference from other equipment
- Long battery life
Ultrasound:
- Requires infrastructure for readers
- Affected by some noisy environments
Infrared:
- Requires infrastructure for readers
- Requires clear line of sight of a maximum of 6–7 metres between ID Tag and reader
- Affected by strong light e.g. direct sunlight
