Gps speed limiter.Introduction to the difference between Beidou positioning and GPS positioning

　　1. Coverage: The Beidou positioning system is a regional navigation system that covers mainland China. The coverage range is approximately 70 ° -140 ° E and 5 ° -55 ° N. GPS is an all-weather positioning system that covers the world. It can ensure that 6-9 satellites can be observed simultaneously at any location and time on Earth (in fact, up to 11 satellites can be observed).

　　2. Number of satellites and orbital characteristics: The Beidou positioning system sets up two geostationary satellites with an equatorial angular distance of approximately 60 ° on the Earth's equatorial plane. GPS sets up 24 satellites on 6 orbital planes, with an equatorial inclination of 55 ° and an equatorial angular distance of 60 ° on the orbital plane. The satellite is in a quasi synchronous orbit and orbits the Earth for 11 hours and 58 minutes.

　　3. Positioning principle: The Beidou positioning system is an active two-way ranging two-dimensional navigation system. The ground center control system solves and provides users with three-dimensional positioning data. The GPS positioning system is a passive pseudocode one-way ranging 3D navigation system. Independently solve their own 3D positioning data by the user's device. The working principle of Beidou brings two problems. Firstly, it loses radio concealment while positioning users, which is quite disadvantageous in the military. Secondly, due to the fact that the equipment must include a transmitter, it is at a disadvantage in terms of size, weight, price, and power consumption.

　　4. Positioning accuracy: The three-dimensional positioning accuracy of the Beidou positioning system is about tens of meters, and the timing accuracy is about 100ns. The GPS three-dimensional positioning accuracy P-code has been improved from 16m to 6m, and the C/A code has been increased from 25-100m to 12m. The timing accuracy was about 20ns recently.

　　5. User capacity: Due to its active bidirectional ranging inquiry response system, the BeiDou positioning system not only receives inquiry signals from the ground center control system but also requires user equipment to transmit response signals to the synchronous satellite. Therefore, the user capacity of the system depends on the allowed channel blocking rate, inquiry signal rate, and user response frequency. Therefore, the user equipment capacity of the Beidou positioning system is limited. GPS is a one-way ranging system, and user devices can perform ranging and positioning as long as they receive navigation messages sent by navigation satellites. Therefore, the capacity of user devices for GPS positioning is infinite.

　　6. Survival capability: Like all positioning satellite systems, Beidou is based on the central control system and satellite operations. However, Beidou's dependence on the central control system is significantly greater because positioning solutions are performed there rather than by user equipment. To compensate for the vulnerability of this system, GPS is developing interstellar horizontal data link technology, so that GPS satellites can operate independently in the event of the main control station being destroyed. The "Beidou" system theoretically excludes this possibility, as once the central control system is damaged, the system cannot continue to operate.

　　7. Real time performance: The positioning application of "Beidou" users needs to be sent back to the central control system, which calculates the user's three-dimensional position data before sending it back to the user. During this process, it needs to go back and forth through the geostationary satellite, and with satellite forwarding, the processing time delay of the central control system is longer. Therefore, for high-speed moving objects, the positioning error is increased.

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