What are the methods of GPS positioning, what are their advantages and disadvantages

1, GPS positioning

GPS is a familiar term, it is by the United States of America to study a way to locate, characterized by: do not need a sim card, do not need to connect to the network, as long as the outdoors, basically anytime, anywhere accurate positioning. However, the time to search for satellites after GPS startup is more, usually takes about 2 minutes (commonly known as cold start, cold start includes ① GPS initial use ② GPS battery depletion ③ power off state move more than 1000 kilometers away or continue to shut down for more than 4 hours).

Advantage: High positioning accuracy, as long as it can receive the positioning signals of four satellites, it can be positioned with an error of less than 5 meters.

Disadvantages: GPS is greatly affected by weather and location. When the weather is bad, or under a viaduct/shade, or in the corner next to a tall building, or in an underground garage or open lower garage (or simply when the sky is out of sight), GPS positioning will be quite affected, or even unable to perform positioning services.

2, LBS (base station) positioning

Base stations include mobile base stations, Unicom base stations and telecom base stations. Base station positioning is through the mobile communication base station signal difference to calculate the location of the phone is located, depending on the location of the location of the nearby base station coverage density, if the base station is more, the positioning is accurate, if it is a mountainous area, the base station is less, the positioning is less accurate, the positioning accuracy is generally in the 50-2000 m. The LBS positioning must be connected to the Internet, the phone is in the state of the sim card registration (wifi in flight mode and pull out the sim card can not be) LBS must be connected to the Internet and the phone must be in sim card registration status (neither turn on wifi in flight mode nor pull out sim card).

Advantages: Convenient, because it receives the signal from the base station through the SIM card for positioning. Theoretically, by calculating the signal difference between the three base stations, you can determine where the phone is located. Therefore, as long as the user's cell phone is within the effective range of the mobile communication network, the location can be positioned at any time without being affected by the weather, tall buildings, location and so on.

Disadvantages: The position coordinate value derived from the signal difference of the base station is obviously inferior to the positioning accuracy of GPS, and is greatly affected by the environment. In the suburbs and rural areas, the mobile station can be positioned within 10-20 meters, but in the urban area, due to the high number of tall buildings and the bad environment of the wave propagation, the signal is difficult to arrive at the mobile station directly from the base station, and it generally has to pass through the refraction or reflection, so the positioning accuracy will be affected. Positioning accuracy will be affected, positioning range of 100 to 200 meters; Secondly, the use of a narrower range, although the LBS will not be affected by the weather, viaducts or tall buildings, but if you exceed the service range of the cell phone, or the phone is located in the number of base stations is not enough, it can not carry out the LBS positioning, from this point of view is not suitable for field use.

3, WIFI positioning

Wifi positioning, as the name implies, there must be wifi around you! The purpose of WiFi positioning is to solve the problem of indoor positioning, the principle is similar to the base station positioning. We know that every wireless AP has a globally unique MAC address, and WiFi positioning relies on detecting all the WiFi access points around the neighborhood. (WiFi Access Point)? WiFi positioning relies on detecting the MAC addresses of all nearby WiFi Access Points, comparing them to the coordinates of the MAC address in the database, and then cross-calculating the location.WiFi positioning is based on the following conditions: 1) Wifi must be turned on, regardless of whether it's connected to a hotspot or not. 2) It must be able to access the Internet, either through mobile data or wifi networking.

Advantages: ① high positioning accuracy, wifi dense crowded places quite accurate; ② fast; ③ around the wifi even if not connected to the localization.

Disadvantages: obvious, ① wifi dependence! --No open wifi can not locate; ② must be in the network state.

4, A-GPS positioning

AGPS is a method to assist GPS positioning. Positioning principle and?GPS?is the same, just add the network assistance, AGPS positioning, there must be a GPS module exists, if there is no GPS module, this positioning is not useful.A-GPS positioning is used to accelerate the positioning speed, due to the cold start of GPS, the search for the star is very slow (you need to head over twenty satellites one by one to search again), about 2 minutes to search for. It takes about 2 minutes to search. After increasing the AGPS positioning can use the base station to locate your position, and then through the network will send this position to the server, the server according to this position will pass through your head at this time the satellite parameters (which several, frequency, position, elevation angle and other information) feedback to your positioning equipment, equipment on the GPS can be very purposeful to search for satellites, at this time your search speed is greatly improved, a few seconds can be located. A few seconds can be positioned.

Advantage: fast star search and positioning, no matter cold start, hot start, seconds.

Disadvantages: must be connected to the Internet, if your device can not access the Internet, or downtime and there is no wifi around, it is not possible to apply the AGPS to achieve the effect of second fix.

5, Beidou positioning

Beidou positioning, simply put, is the domestic GPS, the same principle and GPS positioning, is the use of China's independent research and development of Beidou satellites to carry out positioning, the current largest user is the Chinese military, civilian is not very popular, positioning accuracy compared to the GPS positioning is also a lot worse.

Advantages: domestically produced, safe, and with GPS does not have the communication and targeting, GPS can only tell the user where "I", but the Beidou system not only can tell the user where "I", but also can tell the user But Beidou can not only tell users where "I" am, but also tell users where "my friends" are.

Disadvantages: It is still in the development stage, mainly used in military, civil promotion has not been fully popularized, and the chip cost is high, in the middle and high latitude areas, due to the number of visible satellites of BeiDou is less, the satellite distribution is poor, the positioning accuracy is poor or can not be positioned.

References

360Q&A.360 [cited 2017-12-24]