source:truck tracking webfleet solutions release time:2022-08-12 Hits: Popular:realtime gps tracker online
Due to the limitations of the Meridian satellite system, in 1973 the United States began to plan to develop a new navigation and positioning system, the GPS positioning system. After 20 years of hard work, the system was initially built and put into use in 1993. At this time, the system has a total of It consists of 24 satellites, including Block I experimental satellites and Block II, Block IIA working satellites. After the completion of the GPS navigation constellation, the use of C/A codes for navigation and positioning can also achieve high positioning accuracy. Therefore, considering the huge use of GPS in the military field, in order to prevent the enemy from using GPS to endanger the national security of the United States, the United States defense The Ministry stipulates that the SA technology should be implemented on all working satellites, that is, it is considered to reduce the accuracy of the navigation system. There are two specific technical means:
1. A technology that artificially adds errors to the broadcast ephemeris of the satellite to reduce the accuracy of the satellite ephemeris.
2. Technology, consciously adding a pseudo-random process rapid change to the satellite clock frequency.
On the other hand, in order to prevent the enemy from electronically spoofing and electronically jamming GPS satellite signals, the US Department of Defense has implemented the AS policy. The specific method is to add a strictly confidential W code to the GPS P code. After modulo two addition, a completely secret Y code is generated. Although the AS policy is a defensive measure, it also limits the possibility of unlicensed users to use the Y code, so it is impossible to obtain high-precision ranging codes, which greatly reduces the navigation accuracy.
Later, the GLONASS satellite navigation system managed by Russia announced that it would not implement the SA policy, so the positioning accuracy of its navigation system was much higher than that of the GPS system using the SA policy. Announced in 2009 to suspend the implementation of SA.
As satellite navigation systems play an increasingly important role in various fields of military and civilian use. However, the original GPS system has many shortcomings, such as: 1. It is difficult to receive satellite signals in hidden areas; 2. The energy of C/A code and P code is concentrated near the center frequency and is prone to human interference; 3. L2 carrier Ranging code is not modulated on the device, which makes it impossible for ordinary users to perform dual-frequency ionospheric delay correction, which affects positioning accuracy. Therefore, the C/A code was modulated on the L2 carrier of the navigation satellites of the subsequent Block IIR-M and Block IIF models, and later changed to the L2C code, so that civilian users can also use dual-frequency observation to improve positioning accuracy. Later, the L5 signal was added to the GPS navigation satellite after Block IIF, so that tri-frequency positioning can be used for non-military users.
Read recommendations:
Application introduction in GPS Meteorology.obd2 gps tracker verizon Production
Last article:GPS positioning technology
Next article:Composition of GPS system
Related Information
cat gps tracker sales
2023-04-11GPS Tracking company
2023-04-11Cantrack G05
2023-04-11fleet gps tracking price
2023-04-23gps vehicle tracker distributors
2023-04-11mini gps tracker wholesale
2023-04-23real-time gps tracking
2023-03-16gps tracker app price
2023-04-11gps tracker with magnet wholesale
2023-03-16Car gps tracking Processing
2023-04-23GF20-Mini Magnet GPS Tracker
2022-06-21G500M-Mini GPS Tracker
2022-06-20G900LS 8 Lines-4G Car GPS Tracker
2025-03-31G02M Pet Tracker
2022-06-19TK200AM-Disposable GPS Tracker
2022-06-21Types of GPS Chips Used in Common GPS Receivers
2022-08-17How to use the car GPS navigator.realtime gps tracker online Vendor
2023-05-19The manufacturer believes how to determine the radar, GPS, Beidou and radio positioning.gps tracker
2023-06-17Beidou Navigation GPS
2022-09-27Intelligent GPS anti-theft electronic system
2022-08-26GPS reset did not have a substantial impact on car GPS locators
2023-09-04Pet intelligent positioner escort your pet security safety
2023-02-17About GPS' Third Generation Chips'.gps tracker for bike Factory
2023-07-06Handheld GPS instrument function.simple gps tracking company
2023-07-17Features of GPS navigation map
2022-12-14Brief introduction to GPS principle
2022-12-13The choice of GPS hardware architecture
2022-09-01Gps speed limiter.Basic knowledge and performance indicators of automotive GPS locators
2023-11-09Do gps trackers consume data?
2022-09-16Differences between GPS cold start and hot start
2022-12-30