LORAN
LORAN ( Long Range Navigation ) is a radio navigation system that is primarily used for navigation in the maritime and aviation.
- 5.1 Eurofix
- 5.2 Eloran
- 7.1 documents
- 7.2 Literature
- 7.3 External links
Technology
The current version of LORAN - C is based on transmitting stations that are grouped together to form chains ( chains ). A chain consists of a main transmitter and two to five secondary transmitters which are several hundred kilometers away. The stations transmit in a fixed pattern pulse groups. From the time difference, with the signals arrive at the receiver, he can hyperbolic position lines and calculate its position from the intersection. Therefore, it is a hyperbolic navigation. To achieve a clear identification of the main and secondary channels of a chain and to avoid mutual interference, the individual transmitters do not transmit simultaneously, but by a defined delay time offset from one another. The group repetition interval (Group Repetition Interval, GRI ) and the secondary transmitter delay times (emission delay ) are such that even with distant receiver locations, whether large signal propagation times, no overlap can occur. The Loran-C signal is radiated at a frequency of 100 kHz, with a range of 1000 km is obtained.
Modern receivers offer at reception is good repeatability of up to ten meters. Since the propagation speed of the signal mainly depends on the nature of the earth's surface (water / land, summer / winter), you have to achieve good absolute position accuracy, consider these factors. Without these so-called ASF corrections (additional secondary factors ) the absolute accuracy is a few hundred meters. The geometry, ie the position of the receiver relative to the transmitting stations has a significant influence on the accuracy. Outside the region between the received Loran-C stations, the accuracy strongly of and may well be in the range of several kilometers.
History
Precursor of the LORAN -C system were LORAN -A, whose development was initiated during the Second World War by the U.S. Navy, and its extension LORAN - B, which was not used on the experimental stage addition. LORAN -C achieves a much higher accuracy than LORAN -A, is highly resistant to weather and can be used around the clock with the same precision. The LORAN -C system of the United States was ready for use in 1957 and has been operated since 1958 by the Coast Guard (U.S. Coast Guard ). In 1974, the decision was made to phase out the operation of LORAN -A and LORAN -C explains to the primary navigation system for the coastal waters of the United States and Alaska.
In May 2009, the U.S. announced their Loran- C network shut down for reasons of cost, since now satellite-based navigation is the art. The last U.S. Coast Guard Station, Caribou, Maine, introduced on 1 September 2010 their service. The further development of Eloran service is no longer supported by the United States.
NELS
In Europe, the Northwest European Loran- C System ( NELS ) arose after the U.S. military not continue led the operation of the stations. On 6 August 1992, the four European countries signed with LORAN -C transmitters a contract ( France (2 channels), Germany ( Rantum ), Ireland, the Netherlands and Norway ( Bø and Jan Mayen ). Norway In addition, the stations were Værlandet and Berlevaag created. plans to build a new station in Loophead in Ireland. stations are managed by the respective country and are no longer under military control. on 31 December 1994, the stations that were operated by the U.S. Navy in Europe were are submitted to the respective host country and most technically renewed by this. Due to European NELS Loran- C is used to broadcast differential corrections to the GPS signal (see differential GPS ). this technique is called Eurofix.
Transmitter
Broadcasting stations are not only in the U.S. but operate worldwide. LORAN -C is available in the North Pacific Ocean (including the Bering Sea ), North Atlantic, the Mediterranean, the Baltic and North Sea, the Red Sea and the Persian Gulf. In the Soviet Union, an equivalent system with the name CHAYKA was developed, which, however, was mainly built inland.
The only LORAN -C transmitter site in Germany is the LORAN - C transmitter Rantum on the island of Sylt.
Since 2005, the system builds Saudi Arabia Saudi Positioning System (SPS ) on similar Eurofix a combination of LORAN -C, GPS and DGPS.
LORAN-C transmitters are transmitting power between 100 kW and 4000 kW. When transmitting antennas isolated self-radiating transmission towers are usually used to earth with a top capacity of approximately 190 meters to 220 meters in height, but also transmission towers were built of height above 400 m for some very powerful stations.
The transmitter Minami- Torishima is a transmitting device in the chain Grid 9970 on Minamitori -shima. The transmitter has a transmission power of 4000 kW, making it one of the strongest stations in the world. As a transmitting antenna it uses a 213 m ( up to 1985: 411,48 m) high, radiating transmitting mast.
The transmitter Iwo Jima was a transmitting device in the chain Grid 9970 on Iwo Jima at 24 ° 48 '6 " N, 141 ° 19 ' 30" O24.801666666667141.325. The transmitter had a transmission power of 4000 kW and was one of the strongest stations in the world. In 1965, the 411.48 -meter-high radio mast of the station during maintenance plunged and this also destroyed the transmitter building, together with all technical equipment. The plant was rebuilt, with the new station also received a 411.48 -meter-high radio mast. In September 1993, the plant was shut down and dismantled the antenna mast.
The transmitter Cape Race is a transmitting device in the chain Grid 9930 at Cape Race, at 46 ° 46 '30 " N, 53 ° 10' 30" W46.775 - 53 175. The transmitter has a transmission power of 1800 kW. As a transmitting antenna he used a 411.48 m high, radiating transmitting mast. On 2 February 1993 this transmission tower collapsed. He was replaced by a 260.3 m high, radiating transmitting mast.
List of LORAN -C chains;
List of LORAN -C transmitting stations
Future
Worldwide, the continued existence of the LORAN -C system in the discussion, since there is a much more accurate alternative is available with satellite navigation systems; with modern requirements in the meter and sub-meter can not compete LORAN -C. Due to the propagation characteristics of the waves, for example, an accurate determination of the signal path is extremely difficult.
LORAN -C, however, can be used complementary to GPS signal due to its characteristics. The long-wave LORAN - C signal penetrates even to places where satellite reception due to lack of direct line of sight to the satellites is not possible ( eg in the forest, limited even under water, surrounded by buildings). LORAN -C provides a simple test of integrity, the ' Blinking ' to warn the user in case of malfunction. A targeted disruption of the radiated at high power signal is also in contrast to satellite-based method, quite difficult. An advantage of the system is also that it is not like GPS is under military control. Because of these properties LORAN -C has come in recent years, again more this week, especially as a backup system for GPS. Due to many studies that have demonstrated many of the above shortcomings of GPS as the only navigation system that is both in the U.S. and in Europe, an improved successor system under the name Eloran in the discussion.
The last station of the U.S. Coast Guard introduced on 1 September 2010 their service. Europe, too, is what LORAN-C is concerned, in transition. The NELS contract expired at the end of 2005. However, unlike announced all European stations still in operation (as of March 2007). Currently, the trend in Europe is mainly driven by the UK and France. The future is open, a complete shutdown of the transmitter, however unlikely. Most likely an operation in the framework of the European Union is likely to be.
Eurofix
Other data are transmitted Eurofix extended Loran -C is a data channel via the GPS correction signals UTC time signals, and. In the " Eurofix feasibility phase " currently available to the stations Lessay, Sylt, Værlandet and Bø Eurofix available. The development of Eurofix is being promoted since 1989 by the Delft University of Technology. Together with the correction data ( DGPS ) accuracy at 95 percent of the data is better than 5 meters.
Eloran
The development culminated in Eloran (enhanced LORAN ). Similar to GPS Eloran transmits its own correction data, the so-called additional secondary factor ( ASF). They describe a weather- dependent terrain model, which corrects the near-ground propagation behavior of long-wavelength radio waves. Eloran achieves an accuracy of 10 m or better. It is in the order of GPS, but does not provide height resolution. For this, it has the advantages of LORAN -C, for example, the high noise immunity.
Eloran is established by the GLA (General Lighthouse Authorities of the United Kingdom and Ireland ), as well as by the U.S. as a complementary system to GPS.
Similar systems
The Russian counterpart of LORAN -C is CHAYKA.
Other systems ( ground-based ) radio navigation were and are Decca, OMEGA and Alpha.