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Radar, navigation and tracking systems
Published in Geoff Lewis, Communications Technology Handbook, 2013
This system was designed as a long range (about 1500 km) maritime navigational aid. It is based on three widely spaced high power transmitters, radiating accurately timed 10 μs pulses within a bandwidth of ±10 kHz centred on a carrier frequency of 100 kHz. Again, pairs of transmitters produce hyperbolic electromagnetic energy patterns. A LORAN receiver measures the time of arrival of these pulses to evaluate the distances from each transmitter and, using triangulation, it automatically calculates the position. The 10 μs, 100 kHz pulses can be processed directly and without demodulation using the processing power of a transputer. Using an averaging technique, such a system can resolve the necessary trigonometrical calculations to provide a fix accurate to within about 300 m.
Hyperbolic radio navigation
Published in Mike Tooley, David Wyatt, Aircraft Communications and Navigation Systems, 2017
Loran is an acronym for long range navigation, a system based on hyperbolic radio navigation. The system was developed during the 1940s as Loran- A and has undergone many developments; the current version is Loran-C. Operating in the LF frequency range of 90–110 kHz, the system comprises ground transmitters and monitoring stations. The Loran-C system has a typical range of up to 1000 nm and an accuracy of better than 0.25 nm (460 meters) in the defined coverage areas. Transmitters are grouped together in ‘chains’ thus providing a two -dimensional position fixing capability. The patterns are formed in various ways by master and secondary stations, as illustrated in Figure 14.4.
Navigation
Published in Cary R. Spitzer, Uma Ferrell, Thomas Ferrell, Digital Avionics Handbook, 2017
Loran is used by general-aviation aircraft for en route navigation and for nonprecision approaches to airports (in which the cloud bottoms are more than 400 ft above the runway). It is principally a maritime navaid but may become a backup to GPS for aeronautical users.
Ionospheric delay estimation of Loran skywave using simple cosine model
Published in Electromagnetics, 2023
Kai Zhang, Fan Yang, WeiDong Wang, Chen Zheng, Borong Zou, Hui Li
In order to nearly eliminate the effects of the earth’s ionosphere on users of the Loran, differential or GNSS-assisted methods were specifically incorporated into the system to allow users to automatically correct for the effects of range error induced by the ionosphere. Some users, however, may not have a requirement for nearly complete, automatic correction for ionospheric range error or may not have enough equipment. For these users, we propose a simple method using eight coefficients for ionospheric delay estimation of Loran skywave in this paper. It uses a cosine model based on semi-empirical and semi-measured method, which provides a correction for approximately 90% rms of the ionospheric delay error. Corrections for ionospheric delay error for a single-frequency user are not practical by modeling techniques. This is because small fluctuations in the ionosphere that produce distance errors of seconds to minutes cannot be predicted except by statistical methods. The goal of 90% rms correction of ionospheric time delay estimation is a compromise between two aspects. One is the number of coefficients that signal message needs to broadcast. Another aspect is computing complex ionospheric models. This cosine model is a simpler and more accurate method which combining the physical characteristics of ionosphere and the delay variation law of Loran skywave passing through the ionosphere. It makes a great contribution to reducing the main error source in skywave timing system.
Reference trajectory-based coverage analysis method in three-dimensional space for multi-radio integrated navigation systems
Published in International Journal of Image and Data Fusion, 2020
Jae Hoon Son, Sang Heon Oh, Dong-Hwan Hwang
A research on the multi-radio integrated navigation system has been performed in Korea, in which GPS is integrated with ground-based radio navigation systems such as DME, eLoran, Loran-C, and VOR, KNSS (Korean Navigation Satellite System), and Pseudo-lite (Son et al. 2019a, 2019b). KNSS is a Korean regional navigation system and will be deployed in the near future.