Navigation radar index

visual navigation mark, also called visual navigation mark, is a fixed or floating navigation aid for direct visual observation. Visual AIDS to navigation have recognizable shapes and colors, and can be used to install lamps and other ancillary equipment. Visual navigation AIDS have the advantages of simple equipment, convenient maintenance, low investment and intuitive use. They are widely installed in sea areas and inland rivers, and are the most important, basic and numerous navigational AIDS.

Visual navigation marks include lighthouses, lampposts, beacons, light buoys, buoys, light boats, mooring equipment and navigation marks. Visual navigation mark is a navigation aid that people can directly observe visually, so the shape, color and top mark of its body are often used for sailors to observe during the day. The quality of light is used, that is, the color, rhythm and period of light are used as the characteristics of night recognition. At present, there are 2,137 visual navigation marks in the maritime trunk lines maintained by maritime authorities.

the acoustic navigation mark refers to a navigation aid sign that relies on the generated sound to transmit information to attract the attention of navigators. The acoustic navigation mark, in the weather with poor visibility or in the water, sends out acoustic signals with certain recognition characteristics, so that the ship knows its approximate position and plays a role in warning the danger. According to the media, acoustic navigation AIDS can be divided into air acoustic navigation AIDS and underwater acoustic navigation AIDS.

The air-borne acoustic navigation mark is the earliest and most popular acoustic navigation mark, which uses air as the transmission medium. Aerial acoustic navigation AIDS include fog bell, fog gong, fog horn, fog whistle, fog cannon and fog signal.

underwater acoustic navigation AIDS use water as the transmission medium, and commonly used are underwater clock, underwater positioning system and underwater vibrator. Acoustic navigation marks in water are rarely used.

Radiobeacons include Radarreflector, Radarbeacon, Radarresponder, radio beacon, lorana, loran c, Decca, Omega, Meridian satellite navigation system (TRANSIT), global navigation star system (GLONASS), global positioning system (GPS) and differential global positioning system (DGPS).

the basic meaning of navigation is to guide the movement of carriers (ships, planes and vehicles, etc.), and to guide the movement of carriers by radio technology, which is called radio navigation. The technical devices that can complete certain radio navigation tasks are called radio navigation systems.

at the early stage of the development of ship navigation technology, people only determined the position of the ship by observing the relevant parameters of the targets on the shore and the island or the stars in the sky with their eyesight. Later, ordinary ship navigation equipment such as compass, log, astronomical clock and sextant appeared. Observation with these common navigation devices is often limited in terms of conditions, visible distance or accuracy.

the radio navigation system measures the relevant parameters of the target by using the propagation characteristics of radio waves. Generally speaking, it is not affected by climatic conditions, so it is a very effective navigation method in the case of complex meteorological conditions and poor visibility, and it can successfully complete the navigation task in short, medium and long distances.

the GlobalPositioningSystem (GPS for short) is a satellite positioning system developed by the United States in 1973, which belongs to the global positioning system with dual-frequency ranging. It can provide continuous, real-time and high-precision three-dimensional position, three-dimensional speed and time information for land, sea and air users under all-weather conditions around the world.

in December p>1973, the U.S. department of defense approved the development plan of GPS. The development plan is implemented in three stages: the first stage (1973 ~ 1979) is the system feasibility verification stage; The second stage (1979 ~ 1984) is the system development and test stage; The third stage (starting in 1985) is the practical networking stage of the system, and it was fully networked in 1993.

The system consists of three parts: space constellation, ground monitoring and user equipment.

there are currently 27 working satellites of GPS.

In July p>24, there was one less working satellite of GPS in orbit. At present, there are only 27 working satellites. The satellite serial number of the whole constellation is 1-32, and now the vacant satellites are 2, 12, 16, 3 and 32. Of the six orbital planes A, B, C, D, F, and E, only six stars are distributed in the D and F orbital planes, and the rest of the A orbital planes have four stars (A5 and A6 are vacant), while the B orbital plane has only two stars (B3 and B4), the C orbital plane has five stars (C6 is vacant) and the E orbital plane has four stars (E5 and A6). Of the 27 working satellites, nine stations use cesium clocks, and the rest use rubidium atomic clocks.

Europe and the United States sign GALILEO-GPS agreement

World News (June 29th, 24): The four-year transatlantic dispute between the European Union and the United States has finally ended, and an agreement has been reached on GALILEO-GPS, which will undoubtedly play a positive role in promoting, forming the combination of two satellite navigation systems and their applications. The agreement was signed by Perassi, Vice President of Council of Europe, and Powell, US Secretary of State, allowing each system to work independently and not interfere with each other.

Perassi said that this agreement allows GALILEO in Europe to become the world's civil and commercial satellite navigation standard, which may provide the best service for all users.

the result of four years of arduous negotiations is good news for GALILEO and GPS users all over the world. The agreement confirms that the services of the two constellations are completely compatible, can realize interoperability, can jointly use GPS and GALILEO, and the equipment manufacturing is easier and cheaper. The protocol also stipulates the GALILEO frequency structure, and the key point is that the jamming signal of any party (if necessary, that is, in the theater) is also promised without impacting the whole system.

GALILEO has actually become the world standard for public signals in GNSS mass market. GALILEO can not only be GALILEO's user base, but also millions of GPS users can enter immediately. This means that all users of satellite radio navigation can use a single system with a single receiver or use two systems at the same time.

GALILEO is not only a specialized civil system, but also its commercial nature. The agreement with the United States can quickly introduce GALILEO to all user segments (batch market and professional market) around the world. According to the possible analysis of market research, by 21, the global receiver capacity will reach 3 billion, the annual income will reach 25 billion Euros, and 15, high-grade jobs will be created in Europe.

According to the agreement, two thirds (1.4 billion euros) of the cost of system deployment comes from the market economy, and one third (7 million euros) comes from the government. Such a good prospect has enhanced the competition among the three pre-selected company groups, all of which hope to win the franchise of system operation.

The result of this competition is that GJU is in charge, which is a foregone conclusion at the end of the year, and it will enter the follow-up stage of the plan, opening the way for the final concession contract in 25.

this agreement makes it possible to finalize the system performance index, which is very important for GALILEO to put into operation quickly. After the current development stage (two satellites are already under construction and will be launched at the end of 25, and two other satellites will be put into orbit shortly thereafter), it is expected that 24 other satellites and related ground stations will be deployed before 28. At that time, the system will be put into operation.

GPS provides two kinds of positioning services, namely accurate positioning service (PPS) and standard positioning service (SPS).

the precise positioning service (PPS) will provide the horizontal prediction positioning accuracy of 17.8 m (2 drms) and vertical prediction positioning accuracy of 27.7 m (2 ports), and the speed accuracy of .2 m/s (2 ports) and the time accuracy of 9ns in each dimension in three dimensions. Precise Positioning Service (PPS) adopts P code modulation for dual-frequency transmission and reception. It is only available to military and federal users of the United States and its allies and limited authorized civilian users.

standard location service (SPS) adopts c/a code modulation, single frequency transmission and reception. It is publicly available to civil, commercial and other users. Although standard positioning service (SPS) can provide better positioning accuracy than 3m(2dRMS), for the benefit of the United States, the U.S. Department of Defense artificially introduced selective availability (SA) to reduce its horizontal positioning accuracy to 1m(2dRMS), vertical positioning accuracy to 156m(2a) and time accuracy to 175ns.

because the precise positioning service (PPS) is not publicly provided, and the standard positioning service (SPS) artificially reduces the positioning accuracy, civil users who need high-precision positioning use differential technology to improve the positioning accuracy of the standard positioning service (SPS), thus forming a differential global positioning system, which is called DGPS for short. The simple working principle of DGPS is that the known measuring points are used as differential reference points, a reference GPS receiver is installed in the differential reference station, and the GPS signals are continuously received by the GPS receiver. After processing, they are compared with the known positions of the reference station, and the real-time differential correction values are solved. The differential correction values are transmitted to nearby GPS users by broadcast or data link transmission, so as to correct their GPS positioning solutions and improve the positioning accuracy of users in their local areas.