The meaning & Theory of various positioning methods such as GPS, base station, Beidou, Wifi

1.GPS positioning

GPS is a familiar term for everyone, it is a “meridian” navigation satellite system developed by the US military. GPS is mainly composed of space satellite constellation, ground monitoring station and user equipment. The GPS space satellite constellation consists of 21 working satellites and 3 satellites in orbit. Orbiting satellites are regular. No matter where you are in the world, there are at least 4 satellites above your head at the same time.

GPS positioning terminal to receive signals from those satellites above your head, and then calculate your current position based on the signals. Common terminals include car navigation GPS, built-in GPS for mobile phones, outdoor GPS on foot and GPS for car anti-theft, etc. The accuracy of general civilian level is about 10 meters.

The characteristics of GPS are: no sim card is required, no network connection is required, as long as it is outdoors in an open place, it can basically accurately locate anytime, anywhere. However, it takes more time to search for satellites after GPS is activated, which usually takes about 2 minutes (commonly known as cold start).

2. Base station positioning

The base station positioning is to obtain the location information of the mobile terminal user through the network of the operator of Telecom China Unicom. After the terminal is inserted into the SIM card and turned on, it needs to search the surrounding base station information (that is, to find a signal). More than one base station can be searched, and then the connection with the best signal is automatically selected from these base stations, and the remaining base stations are still searching for them. Once you leave base station A for a distance, the signal from base station A is not as good as base station B, and it will automatically switch to base station B. This is why the mobile phone is also standby for one day, and you consume more power on the train than at home. The mobile phone needs to constantly search and connect to the base station.

Because the signal is easy to be interfered when the base station is positioning, the inaccuracy of its positioning is determined in advance. The accuracy is about 150 meters, and it is basically impossible to drive and navigate. The positioning condition is that the base station must be in a position where the signal of the base station is available, the mobile phone is in the sim card registration state (not possible to turn on the wifi and pull out the sim card in the flight mode), and must receive signals from 3 base stations, whether or not indoors. In addition, if your mobile phone does not have a base station location data packet, you need to connect to the Internet.

3.WiFi assisted positioning

The purpose is to solve the indoor precise positioning, the principle is similar to the base station positioning. The coverage range of a wifi hotspot is only tens of meters. Most wifi hotspots in the world are fixed locations, and they have unique MAC addresses. If the principle of base station positioning is applied, you can obtain fairly accurate location information. Already.

If you have a wireless router set up in your home, always turn it on. Your neighbor is playing Google Maps with his mobile phone on the balcony. It happens that his mobile phone’s wifi is on, but there is no hotspot connected to your home. When your neighbor uses GPS to locate the map accurately, the Google server will record the surrounding wifi hotspot information. It happens that your router is on, and then it is logged to the database, recording your precise location information.

Wi-Fi hotspot positioning conditions: 1. Wi-Fi must be turned on, regardless of whether a hotspot is connected; 2. It must be able to connect to the Internet, mobile data or Wi-Fi. Advantages of wifi positioning: 1. High positioning accuracy, wifi dense crowded places are quite accurate. 2. Fast speed; 3. The surrounding wifi can locate even if it is not connected. Disadvantages: 1. Can’t locate without turning on wifi; 2. Must be connected.

4.AGPS positioning

AGPS is an abbreviation of Assisted Global Positioning System. During AGPS positioning, a GPS module must be present. Without a GPS module, this positioning is useless. When GPS is cold-started, the search speed is very slow, and it takes about 2 minutes to search. What is a cold start? That is, the satellite position information in the GPS is cleared (for example, ① GPS is used for the first time ② GPS battery is exhausted ③ Moved more than 1,000 kilometers or turned off continuously for more than 4 hours in the off state).

AGPS is to first use the base station to roughly locate your location, and then send this location to the server via the network. The server will then feedback the satellite parameters (which number, frequency, location, elevation angle, etc.) passing over your head based on this location To your terminal, GPS can search satellites very purposefully, greatly improving positioning speed.

So, does AGPS consume a lot of traffic? For each positioning, only a dozen kb of traffic, once the positioning is successful, the remaining work is handed over to the GPS module, no need to consume traffic. Therefore, the advantage of AGPS is that the satellite search is fast, no matter how it starts, it is set in seconds. The disadvantage is that it must be connected to the Internet. If your machine cannot access the Internet, you cannot use AGPS to achieve a fixed time.

5. Glonass positioning

Glonass is a positioning system developed by Russia. The principle is the same as GPS, which uses satellites to locate. The difference is that 1.Glonass chip is more expensive than GPS; 2.It has strong anti-interference performance, and GPS may be blind when it is raining in high-rise buildings, but Glonass can still work normally; 3. Northern Hemisphere positioning accuracy is better than GPS 4. Star search is fast.

6. Beidou positioning

To put it simply, it is a domestic GPS. The chip is said to be more expensive than Glonass and the positioning accuracy is more accurate. At present, the largest user is the Chinese military, which is not popular in civilian use. It depends on the policy to buy and sell within the transportation company. One of the highlights is that the Beidou generation can use the satellite above the head to send text messages. It is very practical when there is no mobile phone signal, and it is basically useless when there is a signal.

After understanding so many positioning methods, you will find that as long as we have a positioning terminal (such as a mobile phone), in theory, it can be easily found. With the continuous development of science and technology, the positioning speed is faster, the accuracy is higher, and the coverage is more comprehensive. And our personal privacy, under the monitoring of global satellites, is like the eyes installed in the sky to monitor your position at all times, it will also become a hidden danger.

Positioning technology is widely used in transportation navigation, which can promote the intelligence and refinement of traffic management, greatly improve people’s travel efficiency, and promote the development and application of new technologies such as autonomous driving. Develop a positioning module and load a mobile terminal such as a mobile phone to accurately determine the personal position, which is very important for medical assistance, emergency rescue, anti-theft and other fields. In addition, through the integration with high-tech such as the Internet of Things and big data, it can effectively improve the technological means in the field of auto finance.

Post time: Jan-03-2020