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GPS positioning: GPS (Global Positioning System) is a satellite navigation and positioning system established by the United States. Using this system, users can realize all-weather, continuous and real-time three-dimensional navigation, positioning and speed measurement all over the world; In addition, using the system, users can also carry out high-precision time transmission and high-precision positioning.

Base station positioning: base station positioning is generally applied to mobile phone users. Mobile base station positioning service is also called lbs -- location based service. It obtains the location information (longitude and latitude coordinates) of mobile terminal users through the network of Telecom mobile operators (such as GSM network). The general principle is as follows: the mobile phone measures the downlink pilot signals of different base stations to obtain the toa (time of arrival) of downlink pilots of different base stations. According to the measurement results and combined with the coordinates of the base station, the orientation of the mobile phone can be calculated by using the triangular formula estimation algorithm. The actual azimuth estimation algorithm needs to consider the positioning of multiple base stations (3 or more), so the algorithm is much messy. Generally speaking, the more the number of base stations measured by the mobile station, the higher the measurement accuracy, and the more obvious the improvement of positioning performance.

Due to different positioning principles, there are great differences between the two in the following aspects:

1. Reliability

　　Jiangmen automobile navigator manufacturerIt is understood that the two positioning systems have been verified for a long time and have high reliability. However, because the ownership of GPS satellite belongs to the U.S. government, it is not ruled out that there are certain dangers due to various irresistible factors (such as war, economy, etc.). The base station positioning is based on China's own skills and services, with high reliability.

2. Accuracy

There are many kinds of carriers for GPS positioning. P code is also known as fine code. The positioning accuracy is generally about 30cm, which is generally used by the U.S. military; C / a code is also coarse acquisition code, and the positioning accuracy is slightly poor, generally about 10m. The latter can easily realize real-time positioning because of its simple data processing, low requirements for positioning conditions and no integer ambiguity. Therefore, it has been widely implemented in civil use. On the one hand, the positioning accuracy of the base station is related to the selected positioning skills. In addition, it also depends on the external environment providing services, including radio propagation environment, density and geographical orientation of the base station, as well as the equipment used for positioning. For example, the probability of positioning accuracy within 50m launched by FCC in the United States is 67%, and the probability of positioning accuracy within 150m is 95%.

3. Use cost

The GPS satellite signal used by GPS receiver is completely free, so there is almost no cost for simple GPS positioning. The location of the base station is based on the service of the operator, so it is necessary to pay a certain service fee every month.

4. Scope of cover up

Because GPS positioning uses the signal transmitted from outer space satellites, the signal is very weak, so it can not be positioned normally indoors, in basements, tunnels and other places. However, because 24 satellites around the world are distributed in 6 orbits with an inclination of 55 °, it can ensure that 4 satellites can be received in any direction in the world and provide continuous positioning in a global range. The base station positioning is carried out by the base station set up by the telecom operator, so all mobile phone signals can be positioned normally, and can be positioned normally indoors, basement, tunnel and other places. However, in some remote areas, there may be no or few base stations, so the positioning function may be very poor.

5. Positioning speed

When the GPS receiver is in the cold start, it needs to receive more than four satellites and persist for a period of time before it can make normal positioning. Generally, the cold start positioning time is about 1 ~ 2 minutes. Even for hot start positioning, it usually takes 10 ~ 30 seconds. The general base station positioning generally takes only a few seconds.

To sum up, GPS positioning and base station positioning have their own advantages and disadvantages. Therefore, our terminals use the dual-mode of GPS satellite positioning and base station positioning to achieve a positioning form with higher relative accuracy and wider coverage. This form allows the user's receiver to select GPS satellite positioning where there is satellite signal outdoors, with an error of about 10 meters. When the user enters the underground parking lot or the indoor one cannot receive GPS satellite signal, the locator will actively switch to the base station form, so as to achieve the purpose that the positioning signal will never disappear.

The article comes from Jiangmen vehicle navigatorhttp://m.sdgaokang.cn/