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:
4G GPS Tracker for vehicles price
GF70L-Solar Magnetic Asset GPS Tracker
Last article:GPS positioning technology
Next article:Composition of GPS system
Related Information
gps tracker device
2023-04-11Dog gps tracker sales
2023-04-23GPS Tracker maker
2023-04-11Cantrack GT06
2023-04-23Dog gps tracker wholesaler
2023-04-23simple gps tracking custom
2023-04-23Gps speed limiter company
2023-04-23gps vehicle tracker price
2023-04-23obd2 tracker wholesale
2023-03-164G GPS Tracker for vehicles distributors
2023-04-23TK100 (GT06) Vehicle Tracker
2022-06-20NB20 -4G Bluetooth Smart Pet Tracker
2022-06-21YG119- Hunting Dog GPS tracker
2023-10-074G Wired GPS Tracker PCBA
2022-06-17G200NY -Cow/Camel GPS Tracker
2022-06-21GPS setting RF front end
2022-11-08Introduction to GPS in Wildlife Protection.obd2 gps tracker verizon manufacture
2023-05-06GPS predecessor
2023-06-01GPS space and ground control
2023-06-01Can the car GPS locator be used indoors and underground parking lots?realtime gps tracker online Man
2023-03-25How to buy GPS positioner.obd2 gps tracker verizon
2023-03-14GPS positioner helps logistics and transportation companies manage transparency and intelligence.obd
2023-03-28The Development History of GPS in the United States.4G GPS Tracker for vehicles manufacture
2023-08-19GPS predecessor
2023-06-01There are problems that occur on the four hardware of GPS.obd2 gps tracker verizon distributors
2023-04-14GPS system composition
2022-12-05GPS module with AGPS function
2022-10-12gps vehicle tracker.What happens if GPS fails?
2023-11-09GPS Locator
2022-10-08GPS signal acquisition unit
2022-11-10