# Hyperbolic Asynchronous Method of a Radio Navigation Technique
## 1 Introduction  
The movement of people and things is one of the basic activities that commonly accompanies our existence and forces us to navigate efficiently, i.e., to guide a moving object along a certain trajectory to a designated destination. This process requires locating and determining the position of successive places along which the navigated object moves. This is important in all circumstances, especially in relation to public and private security and also in defense situations. It is also worth noting at this point that there would be no great geographical discoveries without the ability to navigate in endless water or desert areas. In the past, different methods based on observation of the star system have been used in the navigation process. Astronavigation used especially in desert areas or at sea is a great example. In coastal areas, navigation was based on observations of the coastline and objects of known position on land, an example of which are lithhouses--the so-called terraced navigation [1]. An important breakthrough in this area occurred at the beginning of the last century when radio technology was used to determine the current location of objects. In this way, a new field of knowledge and technology was created, called radionavigation [2]. Generally speaking, the location of objects started to be determined with the use of the so-called radioneters cooperating with radio beacons,an example of which is the Consol system [3]. The next step in the development of radionavigation was to develop hyperbolic systems. Examples of such systems used in practice include the GEE system [2], OMEGA system [4], DECCA system [5] and the currently switched off LORAN system [6; 7; 8; 9]. However, in the second half of the last century, with satellite technology, the era of radiolocation of objects based on radio signals transmitted from satellites and then received in the user's terminal began. This represented a major breakthrough in radionavigation, allowing universal access to the radiolocation service. Currently, the most widespread satellite radionavigation system is the American GPS (Global Positioning System) [10; 11]. The second most popular is the Russian GLONASS (GLobalnaya Navigationalnaya Sputnikovaya Sletema) [12]. Besides, the following satellite navigation systems operate to a limited extent in practice in other countries: the Chinese COMPASS or, under another name, BeiDou-2 [13], European GALILEO [14] and Indian IRNSS [15]. The operation of the satellite navigation systems listed above is based on a hyperbolic way of determining the position of an object. As it is known, the basic structure of such a system is formed by a set (the so-called chain) of four stations, one main and three subordinates, which have to work together in synchronous mode. However, the requirement of synchronous cooperation of these stations is a weak point in the operation of such a system. This is due to the fact that in case of damage or intentional destruction of the main station, access to the location service disappears in the area covered by this chain. Moreover, the weakness of all satellite systems is their high susceptibility to interference, especially intentional spoofing or electromagnetic curtains. With the above in mind, at the faculty of Radiocommunication Systems and Networks of the Gdansk University of Technology, on the initiative of the Polish Navy, research was undertaken to develop an asynchronous and self-organizing hyperbolic system for ground navigation as an alternative to the GPS satellite navigation system. Based on the results of these studies, a technological demonstrator of this new system was designed and built, the operation of which was tested in the measurement tests at sea [16]. In this article, the introduction refers to the basics of operation of the classical synchronous hyperbolic system, operating on the basis of the TDOA (Time Difference of Arrival) method.