Global Positioning System (GPS) is a navigation and positioning system based on satellite technology. Its principle is to determine the specific position of the receiver by measuring the distance and position relationship between the satellite and the receiver. The time accuracy of GPS can reach nanosecond level, far exceeding the requirements of daily application.
Theoretically, the time accuracy of GPS system can reach nanosecond level, which is enough to meet the needs of most applications. In practical application, GPS can meet all kinds of occasions that need accurate time reference, such as aviation, telecommunications, finance and other industries. In addition, GPS is also widely used in vehicle navigation, mobile phone positioning, logistics management and other fields, which provides convenience for people's lives.
However, it is worth noting that although the time accuracy of GPS is very high, there are problems of positioning deviation caused by errors and interference, especially in complex environments such as cities. Therefore, when using GPS for positioning, it is necessary to combine other technical means, such as map data correction, to ensure the reliability and accuracy of positioning.
Characteristics of global positioning system
1, global and all-weather continuous navigation and positioning capability. GPS can provide continuous and all-weather navigation and positioning capabilities for all kinds of users anywhere in the world or near-earth space, and users do not need to transmit signals, so it can meet the needs of multiple users.
2. Real-time navigation, high positioning accuracy and short observation time. When GPS is used for positioning, the position data can be obtained many times in1s. This near-real-time navigation capability is of great significance to highly dynamic users, and it can also provide users with continuous three-dimensional position, three-dimensional speed and accurate time information. At present, the real-time positioning accuracy with C/A code can reach 20-50m, the speed accuracy is 0. 1m/s, and the relative positioning accuracy can reach millimeter level after special processing.
With the continuous improvement of GPS system and the continuous update of software, the relative static positioning within 20km only needs 15-20min. When the distance between each mobile station and the reference station is within 15km, the observation time of each mobile station only needs 1-2min, and then it can be located at any time, and each station only needs a few seconds.
3. The site does not require sightseeing: GPS survey only requires the site to be open up and down, so it can save a lot of bidding costs (general bidding costs account for 30% and 50% of the total cost). Because there is no need for intervisibility between points, the positions of points can be sparse or dense as needed, which makes the selection of points very flexible and can also save the measurement of transition points and transition points in classical measurement.
4. It can provide global unified three-dimensional geocentric coordinates: GPS survey can accurately determine the plane position and geodetic elevation of the station at the same time. At present, GPS leveling can meet the accuracy of fourth-class leveling. In addition, GPS positioning is calculated in the global unified WGS-84 coordinate system, so the measurement results around the world are interrelated.
5. Simple instrument operation: With the continuous improvement of GPS receiver, the automation degree of GPS measurement is getting higher and higher. In the observation towel, surveyors only need to set up instruments, connect cables, measure the antenna height and monitor the working state of the instruments, and other observation work, such as satellite capture, tracking observation and recording, is automatically completed by the instruments. After the measurement, just turn off the power supply and put away the receiver, and complete the field data acquisition task.
If continuous observation is needed for a long time at a station, the collected data can be transmitted to the data processing center through data communication to realize full-automatic data collection and processing. In addition, the volume of the receiver is getting smaller and smaller, and the corresponding weight is getting lighter and lighter, which greatly reduces the labor intensity of the measuring author and makes the field work easier.
6. Strong anti-interference ability and good confidentiality: GPS adopts spread spectrum technology and pseudo-code technology, and users only need to receive GPS signals, and they will not transmit signals themselves and will not be interfered by other external signal sources.
7. Multi-function and wide application: GPS is a dual-use system for military and civilian use, with a wide range of applications. Specific application examples include: car navigation and traffic management, patrol car management, road engineering, personal positioning and navigator, etc.