GPS container tracking

GPS Positioning Principle The GPS receiver can receive time information accurate to nanoseconds that can be used for timing; forecast ephemeris used to predict the approximate location of the satellite in the next few months; used to calculate the satellite coordinates required for positioning Broadcast ephemeris, with an accuracy of a few meters to tens of meters (different satellites, changing at any time); and GPS system information, such as satellite status.


The GPS receiver measures the distance from the satellite to the receiver. It is called pseudorange because it contains the error of the receiver satellite clock and the atmospheric propagation error. The pseudorange measured by the 0A code is called the UA code pseudorange, and the precision is about 20 meters. The pseudorange measured by the P code is called the P code pseudorange, and the precision is about 2 meters.


The GPS receiver decodes the received satellite signal or uses other techniques to remove the information modulated on the carrier and recover the carrier. Strictly speaking, the carrier phase should be referred to as the carrier beat frequency phase, which is the difference between the received satellite signal carrier phase affected by the Doppler shift and the phase of the receiver local oscillator generated signal. Generally, the epoch time determined by the receiver clock is measured, and the tracking of the satellite signal is kept, and the phase change value can be recorded, but the initial phase values of the receiver and the satellite oscillator at the time of starting the observation are unknown. The phase integer of the epoch is also unknown, that is, the whole week ambiguity can only be solved as a parameter in data processing. The accuracy of the phase observation is as high as millimeter, but the premise is that the whole-circumference ambiguity is solved. Therefore, the phase observation value can be used only when the relative positioning and the continuous observation value are obtained, and the positioning accuracy is better than the meter level. Phase observations can be used.


According to the positioning method, GPS positioning is divided into single point positioning and relative positioning (differential positioning). Single point positioning is a way to determine the position of the receiver based on the observation data of a receiver. It can only be measured by pseudo-range observation and can be used for rough navigation and positioning of vehicles and ships. Relative positioning (differential positioning) is a method of determining the relative position between observation points based on observation data of two or more receivers. It can use either pseudo-range observation or phase observation. Geodesy or engineering measurement should be performed. Phase observations are used for relative positioning.


The GPS observations include errors such as the clock difference between the satellite and the receiver, the atmospheric propagation delay, and the multipath effect. They are also affected by the satellite broadcast ephemeris error during the positioning calculation. Most of the common errors are caused by relative positioning. Offset or weaken, so the positioning accuracy will be greatly improved. The dual-frequency receiver can offset the main part of the ionospheric error in the atmosphere according to the observation of two frequencies. When the accuracy is high and the distance between receivers is long (the atmosphere is obviously different) ), should use dual-frequency receiver.


In the positioning observation, if the receiver moves relative to the surface of the earth, it is called dynamic positioning, such as pseudo-single point positioning with accuracy of 30-100 meters for rough navigation and positioning of vehicles and ships, or for urban vehicle navigation and positioning. Pitch-precision differential positioning with meter-level accuracy, or centimeter-level phase differential positioning (RTK) for measuring stakeout, etc. Real-time differential positioning requires a data link to transmit observations from two or more stations in real time. In the positioning observation, if the receiver is stationary relative to the surface of the earth, it is called static positioning. When performing control network observation, it is generally observed by several receivers in this way. It can play GPS at the most limit. Positioning accuracy, a receiver dedicated to this purpose is called a terrestrial receiver and is the best performing class in the receiver. At present, GPS has been able to meet the accuracy requirements of crustal deformation observation, and IGS's perennial observing stations have been able to form a millimeter-scale global coordinate framework.


How the GPS system forms a GPS system consists of three parts: the space part - the GPS satellite constellation; the ground control part - the ground monitoring system; the user equipment part - the GPS signal receiver. GPS Tracker Definition GPS Tracker is a terminal with built-in GPS module and mobile communication module. It is used to transmit the positioning data obtained by the GPS module to a server on the Internet through the mobile communication module (gsm/gprs network). Realize the location of the terminal on the computer. GPS Tracker for children's and elderly's whereabouts, road inspection, valuable cargo tracking, tracking and service dispatch, private detective tools, personal property tracking, pet tracking, wildlife tracking, freight industry, bank transport truck, military Police exercise control, inspection tracking, official vehicle management, etc. Basic functions of GPS tracker 1) Positioning function: immediate positioning, timing positioning.


2) Two-way conversation: The authorization number corresponding to the button can be set separately. When the button is pressed, the authorized number can be dialed and the call can be answered.


3) Alarm function: emergency alarm, displacement alarm, overspeed alarm, cross-section alarm, low-power alarm, anti-theft alarm.


4) Electronic fence: The central management personnel can set the terminal driving area. When the terminal exceeds the preset restricted area, it will automatically send alarm information to the monitoring platform and send a short message to the supervised mobile phone.


5) Remote monitoring: The monitoring number can be set. When the number is dialed to the terminal, the terminal will automatically answer the call, thus playing the monitoring effect.


6) Auto Sleep: Built-in vibration sensor will automatically enter the sleep state if there is no vibration within the specified time.


  GPS Tracker Service Platform The GPS Tracker Service Platform is a monitoring and dispatching system based on GPRS and INTERNET communication networks. It consists of a central end and a client. The system architecture uses B/S or C/S technology. The central end of the central end uses fixed IP access to receive and process various data submitted by the GPS terminal through the mobile network, such as the current location information of the terminal, various alarm information of the terminal, etc., and simultaneously process various kinds of submissions from the client. Query request. The central end consists of hardware and software, and the software technology includes database technology, GIS technology, load balancing technology, and network protocol technology. Client client hardware can be divided into computers, mobile phones, and PDAs. If the client is a computer, it needs to access the Internet. If the client is a mobile phone or PDA, it needs to access wireless Internet services such as CMWAP, CMNET, and CMCARD. The use of GPS trackers is mainly for positioning and navigation of moving objects such as ships, automobiles and airplanes.


E.g:


1. Marine ocean navigation and inbound water diversion


2. Airplane route guidance and approach landing


3. Auto navigation


4. Ground vehicle tracking and urban intelligent traffic management


5. Emergency rescue


6. Personal travel and field adventures


7. Personal communication terminal (integrated with mobile phone, PDA, electronic map, etc.)


1. Time synchronization of power, post and telecommunications, communication and other networks 2. Accurate time grant 3. Accurate frequency granting 1. Various levels of geodetic survey, control measurement 2. Road and various line lofting 3. Underwater terrain Measurement 4. Crustal deformation measurement, dam and large building deformation monitoring 5. GIS application 6. Construction machinery (tire crane, bulldozer, etc.) control 7. Precision agriculture


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