Schematic diagram of satellite positioning (taken from the network)
Principle of satellite positioning (picture taken from network)
Indoor positioning, on the other hand, is similar in overall topological principle, and is combined by base stations (equivalent to satellites) and tags (i.e. terminals). However, according to the available technologies and technical characteristics of indoor positioning, it can be divided into many types, and the precise definition varies according to different needs. Perhaps the higher the accuracy, the better, because the higher the accuracy, the higher the corresponding cost!
Indoor positioning comparison
Comparison of indoor positioning technologies
The first generation: existence and identification technology, which can also be called early zero-dimensional positioning.
Mainly use passive RFID technology, such as UHF UHF. The advantages are that the tag (terminal) does not need power supply, the cost is low, and the recycling process is not needed. The disadvantage is that the farthest recognition distance is about 10 m, usually 1~2 m, which is close to metal and liquid, and the recognition distance needs to be broken again.
The second generation: coarse distance recognition, which can carry sensing information.
Active technologies, including WIFI, BLE, Zigbee, Sub 1G, Lora, etc. The positioning accuracy of the instrument can be achieved by RSSI and three-point positioning algorithm. The tag (terminal) is powered by battery, which can increase various interactive functions, such as key pressing, screen display, temperature and humidity detection, etc.
The third generation: accurate positioning and ranging, mainly represented by UWB.
This paper mainly uses the technical characteristics of ultra-wideband to optimize the signal interference with ultra-short pulse signals. WEWILLS uses the time-of-flight algorithm, and the accuracy can reach 10cm. The disadvantage is that the current cost is not low enough, and it is mainly used in industrial fields, such as energy buildings (electric power, water conservancy, thermal power generation, etc. ), industrial intelligent manufacturing, personnel control of public security and judicial departments, tunnel construction (subway, high-speed tunnel, mine). At present, the technical solutions adopted by UWB manufacturers are consistent, and the biggest difference will be process service and landing experience.
According to the requirements of different application scenarios, the definition of accuracy will be different, such as many rooms in nursing homes. If the room needs to be determined, it can be realized by UWB, Bluetooth AOA, Bluetooth beacon, sub 1G, UHF, etc. (Of course, the difference in characteristics of each scene will determine the final technical selectivity). For example, if you need to know whether you are in bed, desk or toilet, you can basically only use UWB or Bluetooth AOA.
Generally speaking, UWB is mainly used indoors and is the high-end representative of indoor positioning, while satellite positioning such as GPS Beidou is mainly used outdoors and is the representative of outdoor high-end positioning. There has been a great difference between the two in application scenarios.
Extended knowledge
Ultra-wideband and satellite positioning (GPS and Beidou, etc. ) There are also great differences in product characteristics:
1. Satellite positioning products usually need to be equipped with mobile network modules, such as 2G/3G/4G/NB, etc. , used to upload satellite data.
2. The power consumption of satellite positioning is much greater than that of UWB, so if 1 month is used on average, the transmission interval of GPS is usually in minutes or even hours, while that of UWB is usually in seconds.