So far it is of little help for a survey navigator, that in the 80's satellite navigation systems on worldwide base will allow fixes continously in real time with an accuracy of ten to hundred feet.
Instead he has to cope with existing facilities still for several years. Especially on the southern hemisphere groundbased radio-navaids are rare and the Transit-Satellite-System allows its lowest sporadic fix frequency in the equatorian region.
This paper will present a survey of methods how presently available navaids maybe exploited to achieve optimal navigation and positioning results as they are needed for research-vessels in areas not covered by accurate radionavigation facilities.
Methods for improvement of groundbased radionavigation systems are discussed for exploitation of existing facilities beyond their normally useable range and to set up own navigational buoys at deep sea to obtain a continous real time position information.
A considerable number of radionavigation systems and devices are scattered throughout the radiofrequency spectrum. The casual observer or even the scientist who has studied a particular system in depth may wonder why so many frequency assignments for navigation exist. The choice of frequency which basically defines the wave propagation mode is far from arbitrary, e.g. the particular requirement' for very long range navigation is met only by few propagation modes.
Accuracy of any system IS Inverse proportional to distance. This applies more severely to systems with complex wave propagation. It means that obtainable accuracy for very long range systems is largely an academic matter. In cases, where is no other choice even low accuracy "back Up" systems may be of enormous value also when the uncertainly is one mile or more.
There are only few radionavigation aids, which are useable for very long range operation. The most important are:
Loran C, Omega and the Navy VLF Communication and Navigation Systems. Using these facilities the user has normally no influence to improvements of the transmitter systems. The only thing he can do is to evaluate his receiving and data handling equipment to harvest the full potential of obtainable information.
If the user really needs more accurate information, he may obtain it by employing his own deep-sea navigational buoys for active and differential navigation.
Normally radio propagation is straightforward like visible light. This fact would make long range navigation along the earth surface impossible unless transmitter and receiver are elevated over the horizon. Beyond the horizon transmissions are feasible by four propagation modes.
