LORAN ( eng. LO ng RA nge N avigation ) is a ground-based radionavigation system . The LORAN system was developed by and was widely used by the US and British naval ships during the Second World War . In a modified form was used by the Air Force , carrier-based naval aviation and US Coast Guard aircraft until 1980. Until recently, it was used for the needs of civil aviation .
Working Principles
Pulse-phase difference-ranging system LORAN-C operates at a frequency of 100 kHz. At these frequencies, the absorption of radio waves in the ionosphere can be significant, especially at large angles of incidence. The LORAN-C system belongs to the class of hyperbolic systems, although it is based on measuring not the phases, but the delays of the pulses received from the chain of transmitting stations. In each chain, one of the stations is leading, and the others are driven. All of them are synchronized exactly. The receiver measures the accuracy of the arrival of pulses with an accuracy of 0.1 µs, and if a ground wave is used, the location can be determined with an accuracy of 150 m at distances of up to 1500 km (at sea). In general, the signal is the sum of the earth wave and the signals reflected one or several times from the ionosphere. At distances of more than 2000 km, the ionospheric wave prevails and the accuracy will depend on the state of the ionosphere. Tests have shown that in some cases errors may occur in several kilometers. Thus, even under ideal conditions, the LORAN-C system will not have the accuracy that the GPS and GLONASS satellite systems provide.
Creation
The following private contractors were responsible for the technical implementation of the tactical navigation system of the last modification ( Tactical LORAN ) for military needs:
- Lear Siegler , Grand Rapids , MI ;
- Sperry Rand Corp. , Great Neck , Long Island ;
- Teledyne, Inc. , Los Angeles , California .
The system is intended for use by fighter-bombers, assault and military transport aircraft. The overall management of the work program from the US Air Force was carried out by the Electronic Systems Systems , Hanscom Field , Massachusetts [1] .
Modernity
To date, the LORAN-C navigation system has 34 chains in the world, covering the territory of the United States, Northern Europe and the adjacent sea areas in the northern hemisphere. LORAN-C receivers are equipped with individual terminal samples of the American Omnitracs system. In Russia, a system of similar purpose is being used as LORAN-C, which is called the “ Seagull ”.
In November 2009, the US Coast Guard announced that the LORAN-C system is not required for marine navigation. This decision placed the continued existence of LORAN and eLORAN in the United States at the discretion of the Secretary of the Department of Homeland Security. [2] In accordance with the appropriations act of the US Department of Homeland Security, the US Coast Guard stopped transmitting all LORAN-C signals on February 8, 2010. This termination did not affect US participation in the Canadian LORAN-C Russian-American or Canadian network. US participation in these networks continued temporarily in accordance with international agreements. [3]
Users of the LORAN-C system were encouraged to use the GPS system for navigation. From August 1, 2010, the work of the American LORAN-C stations as part of the Russian-American chain was discontinued, and as of August 3, 2010, as part of the US-Canadian chain. Thus, at present, the operation of the LORAN-C system in the United States is fully completed. [four]
It is assumed that some of the objects of the old LORAN system will be used in the updated eLORAN system, which is characterized by the use of new type of equipment with digital signal processing, ensuring the accuracy of determining the coordinates, comparable to the SNA . eLORAN will also be included in the single-time signaling system. The eLORAN system is planned to be developed and used in the future as an auxiliary in conjunction with global satellite navigation systems. According to experts, one of the important qualities of this system is its resistance to interference associated with the use of a range of long radio waves for transmitting signals. While for the GPS satellite system confirmed the possibility of setting intentional interference and disruption of the normal operation of the system.
Notes
- ↑ Statement of Lt. Gen. Otto J. Glasser, Deputy Head of Staff, Research and Development, Headquarters, US Air Force . / Department of Defense Appropriations for Fiscal Year 1973: Hearings on HR 16593. - February 21, 1972. - Pt. 4 - P. 936.
- ↑ Senate committee letter Archived December 12, 2009.
- ↑ US Coast Guard Navigation Center
- ↑ LORAN-C General Information - USCG Navigation Center
Literature
- Foreign Military Review 1981 number 12, p. 58-60. Publisher "Red Star" Moscow.
- Foreign Military Review 1985 № 7, p. 66-71. Publisher "Red Star" Moscow.
- Foreign Military Review 1988 № 2, p. 65. Krasnaya Zvezda Publishing House, Moscow.
Links
- List of stations Laurent-S (him.)
- eLoran Technologies (eng.)