The age of all-things interconnection is also king of data. However, in many cases, lack of corresponding location information means that the data is "chaotic" and the available value is greatly reduced. With the booming development of the Internet of Things industry in these two years, the demand for positioning technology in various Internet of Things applications scenarios has also been greatly enhanced. Below we introduce several indoor and outdoor positioning technologies.
1, RFID indoor positioning technology
Radio frequency identification indoor positioning technology uses radio frequency mode, the fixed antenna to the radio signal into an electromagnetic field, attached to the tag of the goods after the magnetic field generated by the induction current to send out the data to exchange data to achieve the purpose of identification and triangulation.
However, it can get centimeter-level positioning accuracy information in a few milliseconds. Due to the advantages of non-line-of-sight distance and so on, the transmission range is very large, and the volume of identification is relatively small and the cost is relatively low. But it does not have the ability to communicate, anti-interference ability is poor, not easy to integrate into other systems, and the user's security and privacy and international standardization are not perfect.
RFID indoor positioning has been warehouses, factories, shopping centers widely used in goods, goods circulation positioning.
2, Wi-Fi indoor positioning technology
Wi-Fi positioning technology, there are two, one is through mobile devices and three wireless network access point wireless signal strength, through the differential algorithm to more accurately triangulate people and vehicles. The other is to record a large number of signal points at a fixed point in advance and determine the position by comparing the signal strength of the newly added device with the one with a huge amount of data.
Wi-Fi positioning can realize complex and large-scale positioning, monitoring and tracking tasks in a wide range of applications with high overall accuracy. However, the accuracy of indoor positioning can only reach about 2 meters, which can not be accurately located. Due to the popularity of Wi-Fi routers and mobile terminals, the positioning system can share the network with other customers, the hardware cost is low, and Wi-Fi positioning system can reduce the possibility of radio frequency (RF) interference.
Wi-Fi positioning for positioning of people or vehicles navigation can be in the medical institutions, theme parks, factories, shopping malls and other needs of the positioning of navigation occasions.
3, ultra-wideband (UWB) positioning technology
Ultra-wideband technology is emerging in recent years a new, very different from the traditional communication technologies for wireless communications technology. Instead of using carriers in traditional communication systems, it transmits data on the order of 3.1 to 10.6 GHz by sending and receiving very narrow pulses of nanoseconds or microseconds. At present, countries including the United States, Japan and Canada are studying this technology and have good prospects in the field of wireless indoor positioning.
UWB technology is a high transmission rate, low transmission power, penetration and is based on very narrow pulse wireless technology, no carrier. It is these advantages that have given it more accurate results in the field of indoor positioning. UWB indoor location technology often uses the TDOA demo ranging location algorithm, which is the time difference between the arrival of the signals. UWB systems located by hyperbolic intersection include radio systems that generate, transmit, receive and process very narrow pulse signals. UWB indoor positioning systems include UWB receivers, UWB reference labels and active UWB labels. The UWB receiver receives the UWB signal transmitted by the tag during the positioning process and obtains signals with valid information by filtering the various noise interferences contained in the electromagnetic wave transmission process. Then, the central processing unit calculates and analyzes the positioning of the UWB signal.
Ultra-wideband can be used for indoor precise positioning, such as the location of battlefield soldiers to find, robot motion tracking. Compared with the traditional narrowband system, the UWB system has the advantages of strong penetrating power, low power consumption, good anti-jamming effect, high safety, low system complexity and accurate positioning accuracy. Therefore, UWB technology can be applied to indoor stationary or moving objects as well as people's position tracking and navigation, and can provide very accurate positioning accuracy. According to different companies using different technical means or algorithms, the accuracy can be maintained at 0.1 m ~ 0.5 m.
4, geomagnetic positioning technology
The Earth can be thought of as a magnetic dipole, one of which is near the geographic north pole and the other near the geographical south pole. Geomagnetic field includes the basic magnetic field and magnetic field changes in two parts. The basic magnetic field is the main part of the geomagnetic field, originated in the Earth's interior, relatively stable, part of the static magnetic field. The changing magnetic field includes various short-term changes of the geomagnetic field, which mainly originate inside the Earth and are relatively weak.
Reinforced concrete structures in modern buildings can disrupt geomagnetism locally and compasses can be affected as well. In principle, non-uniform magnetic field environment will produce different magnetic field observations due to different paths. This is called IndoorAtlas positioning technology, it is the use of geomagnetic indoor indoors to make such changes, and the navigation accuracy can reach 0.1 meters to 2 meters.
However, using this technology for navigation is still slightly troublesome. You need to upload the floor plan of the interior to the map cloud provided by IndoorAtlas, and then you need to use its mobile client to field record the geomagnetic field in different directions at the target location. The recorded geomagnetic data will be uploaded by the client to the cloud so other people can use the recorded geomagnetic data for precise indoor navigation.
In 2014, Baidu strategically invested in IndoorAtlas, a developer of geo-positioning technology, and in June 2015 announced the use of its geo-location technology in its own map application, in conjunction with Wi-Fi hotspot maps and inertial navigation. High precision, publicity commercial applications, you can reach the rice level positioning standards, but the magnetic signal is subject to the changing environment of electrical and magnetic signal interference, the positioning results are unstable, the accuracy will be affected.
5, ultrasonic positioning technology
Ultrasound positioning technology by installing multiple ultrasonic speakers indoors, can be issued by the terminal microphone to detect the ultrasonic signal. Through the arrival time difference between different sound waves, it is estimated that the terminal's position?
Because the transmission speed of sound waves is much lower than that of electromagnetic waves, the realization of the system is very difficult. The system can be wirelessly synchronized very easily and then sent by an ultrasonic transmitter. The receiver receives the signals by using a microphone and can calculate its position.
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