1. The GPS satellite constellation consists of 21 working satellites and 3 on-orbit standby satellites that make up a GPS satellite constellation, which is designated as (21+3) GPS constellation. Twenty-four satellites are evenly distributed in six orbital planes. The inclination of the orbit is 55 degrees. Each orbital plane is 60 degrees apart. That is, the ascending orbits of the orbits differ by 60 degrees each. The angles of ascending pitch between the satellites in each orbital plane are different by 90 degrees. The satellites in one orbital plane are 30 degrees ahead of the corresponding satellites in the adjacent orbital plane on the west.
In the 20,000 km altitude GPS satellites, when the Earth rotates for a week for the stars, they run around the earth for two weeks, that is, when the time around the earth is 12 stars. In this way, for ground-based observers, the same GPS satellite will be seen 4 minutes in advance every day. The number of satellites above the horizon varies with time and place, with a minimum of 4 and a maximum of 11 visible. When using GPS signals for navigation and positioning, in order to settle the three-dimensional coordinates of the station, four GPS satellites must be observed, which is called a positioning constellation. The geometrical position distribution of the four satellites during the observation process has a certain influence on the positioning accuracy. For a certain place, you can't even measure the exact point coordinates. This time period is called “gap sectionâ€. However, this time gap segment is short-lived and does not affect all-weather, high-precision, continuous real-time navigation and positioning measurements in most parts of the world. The GPS work satellite number is basically the same as the test satellite.
2. Ground Surveillance System For navigation and positioning, GPS satellites are a dynamic known point. The position of the star is calculated based on the ephemeris emitted by the satellite—parameters describing the movement of the satellite and its orbit. The ephemeris broadcast by each GPS satellite is provided by the ground surveillance system. Whether the various equipment on the satellite is working properly and whether the satellite has been operating along a predetermined orbit must be monitored and controlled by the ground equipment. Another important role of the ground monitoring system is to keep the satellites at the same time standard—the GPS time system. This requires the ground station to monitor the time of each satellite and find the clock difference. It is then sent to the satellite by the ground injection station, which then sends the navigation message to the user equipment. The GPS monitoring satellite ground monitoring system includes a master control station, three injection stations and five monitoring stations.
3. The task of the GPS signal receiver GPS signal receiver is to be able to capture the signals of the satellites to be tested selected according to certain satellite altitude cutoff angles, and track the operation of these satellites to transform and amplify the received GPS signals. And processing, in order to measure the GPS signal propagation time from the satellite to the receiver antenna, interpret the navigation message sent by GPS satellites, and calculate the three-dimensional position, position, and even three-dimensional speed and time of the station in real time.
The navigation and positioning signal sent by GPS satellites is an information resource that can be shared by numerous users. For the vast land, sea and space users, as long as the user has a receiving device capable of receiving, tracking, transforming and measuring GPS signals, ie a GPS signal receiver. You can use GPS signals for navigation and positioning measurements at any time. Depending on the purpose of use, the GPS signal receivers required by users vary. At present, there are dozens of factories in the world that produce GPS receivers and there are hundreds of products. These products can be classified according to principle, purpose, function, and the like.
In static positioning, the GPS receiver is fixed in the process of capturing and tracking GPS satellites. The receiver measures the propagation time of the GPS signal with high precision, and uses the known position of the GPS satellite in orbit to solve the position of the receiver antenna. Three-dimensional coordinates. Dynamic positioning uses a GPS receiver to determine the trajectory of a moving object. The moving object on which the GPS signal receiver is located is called a carrier (such as a sailing ship, an airborne aircraft, a walking vehicle, etc.). The GPS receiver antenna on the carrier moves relative to the earth during the tracking of the GPS satellites. The receiver uses GPS signals to measure the state parameters of the motion carrier in real time (instantaneous three-dimensional position and three-dimensional velocity).
Receiver hardware and in-camera software and GPS data post-processing software packages constitute a complete GPS user equipment. The structure of the GPS receiver is divided into two parts: an antenna unit and a receiving unit. For geodesic receivers, the two units are generally divided into two separate components. During the observation, the antenna unit is placed on the station, the receiving unit is placed in the appropriate place near the station, and the cable is used to connect the two units. A whole machine. Some also make the antenna unit and the receiving unit into a whole, and place it on the measuring station when observing.
GPS receivers generally use a battery as a power source. At the same time, two kinds of DC power sources outside the machine are used. The purpose of setting the battery in the battery is to continuously observe the battery without replacing the external battery. During the use of the off-board battery, the on-board battery is automatically charged. After shutdown, the internal battery powers the RAM memory to prevent loss of data.
In recent years, many types of GPS geodetic receivers have been introduced in China. When various types of GPS geodetic receivers are used for precise relative positioning, their dual-frequency receiver accuracy can reach 5MM+1PPM. D, single-frequency receiver accuracy within a certain distance up to 10MM +2 PPM. D. For differential positioning its accuracy can reach sub-meter to centimeter level.
At present, various types of GPS receivers are getting smaller and lighter, and they are lighter in weight and easier to observe in the field. GPS and GLONASS-compatible GPS receivers have been introduced.
In the 20,000 km altitude GPS satellites, when the Earth rotates for a week for the stars, they run around the earth for two weeks, that is, when the time around the earth is 12 stars. In this way, for ground-based observers, the same GPS satellite will be seen 4 minutes in advance every day. The number of satellites above the horizon varies with time and place, with a minimum of 4 and a maximum of 11 visible. When using GPS signals for navigation and positioning, in order to settle the three-dimensional coordinates of the station, four GPS satellites must be observed, which is called a positioning constellation. The geometrical position distribution of the four satellites during the observation process has a certain influence on the positioning accuracy. For a certain place, you can't even measure the exact point coordinates. This time period is called “gap sectionâ€. However, this time gap segment is short-lived and does not affect all-weather, high-precision, continuous real-time navigation and positioning measurements in most parts of the world. The GPS work satellite number is basically the same as the test satellite.
2. Ground Surveillance System For navigation and positioning, GPS satellites are a dynamic known point. The position of the star is calculated based on the ephemeris emitted by the satellite—parameters describing the movement of the satellite and its orbit. The ephemeris broadcast by each GPS satellite is provided by the ground surveillance system. Whether the various equipment on the satellite is working properly and whether the satellite has been operating along a predetermined orbit must be monitored and controlled by the ground equipment. Another important role of the ground monitoring system is to keep the satellites at the same time standard—the GPS time system. This requires the ground station to monitor the time of each satellite and find the clock difference. It is then sent to the satellite by the ground injection station, which then sends the navigation message to the user equipment. The GPS monitoring satellite ground monitoring system includes a master control station, three injection stations and five monitoring stations.
3. The task of the GPS signal receiver GPS signal receiver is to be able to capture the signals of the satellites to be tested selected according to certain satellite altitude cutoff angles, and track the operation of these satellites to transform and amplify the received GPS signals. And processing, in order to measure the GPS signal propagation time from the satellite to the receiver antenna, interpret the navigation message sent by GPS satellites, and calculate the three-dimensional position, position, and even three-dimensional speed and time of the station in real time.
The navigation and positioning signal sent by GPS satellites is an information resource that can be shared by numerous users. For the vast land, sea and space users, as long as the user has a receiving device capable of receiving, tracking, transforming and measuring GPS signals, ie a GPS signal receiver. You can use GPS signals for navigation and positioning measurements at any time. Depending on the purpose of use, the GPS signal receivers required by users vary. At present, there are dozens of factories in the world that produce GPS receivers and there are hundreds of products. These products can be classified according to principle, purpose, function, and the like.
In static positioning, the GPS receiver is fixed in the process of capturing and tracking GPS satellites. The receiver measures the propagation time of the GPS signal with high precision, and uses the known position of the GPS satellite in orbit to solve the position of the receiver antenna. Three-dimensional coordinates. Dynamic positioning uses a GPS receiver to determine the trajectory of a moving object. The moving object on which the GPS signal receiver is located is called a carrier (such as a sailing ship, an airborne aircraft, a walking vehicle, etc.). The GPS receiver antenna on the carrier moves relative to the earth during the tracking of the GPS satellites. The receiver uses GPS signals to measure the state parameters of the motion carrier in real time (instantaneous three-dimensional position and three-dimensional velocity).
Receiver hardware and in-camera software and GPS data post-processing software packages constitute a complete GPS user equipment. The structure of the GPS receiver is divided into two parts: an antenna unit and a receiving unit. For geodesic receivers, the two units are generally divided into two separate components. During the observation, the antenna unit is placed on the station, the receiving unit is placed in the appropriate place near the station, and the cable is used to connect the two units. A whole machine. Some also make the antenna unit and the receiving unit into a whole, and place it on the measuring station when observing.
GPS receivers generally use a battery as a power source. At the same time, two kinds of DC power sources outside the machine are used. The purpose of setting the battery in the battery is to continuously observe the battery without replacing the external battery. During the use of the off-board battery, the on-board battery is automatically charged. After shutdown, the internal battery powers the RAM memory to prevent loss of data.
In recent years, many types of GPS geodetic receivers have been introduced in China. When various types of GPS geodetic receivers are used for precise relative positioning, their dual-frequency receiver accuracy can reach 5MM+1PPM. D, single-frequency receiver accuracy within a certain distance up to 10MM +2 PPM. D. For differential positioning its accuracy can reach sub-meter to centimeter level.
At present, various types of GPS receivers are getting smaller and lighter, and they are lighter in weight and easier to observe in the field. GPS and GLONASS-compatible GPS receivers have been introduced.
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