Electronic Navigation Systems are continually developing in order to provide pilots and captains the ability to precisely navigate both ships and aircraft under even the most treacherous of conditions. Modern technological advances have changed the way navigators estimate time, location and distance to destination. Among the electronic navigational instruments used in contemporary society are radar devices including the DECCA and LORAN. GPS is also a commonly used electronic navigational system that has afforded pilots the ability to estimate distance and location with high precision. Electronic navigation has enabled pilots of aircraft to make estimates that are within a 90% or more accuracy range. The primitive systems utilized by early navigators would never approach the precision of modern day systems. Both electronic navigation and instruments used historically for navigational purposes will be explored in greater detail below.
The history of navigation is varied. In times of old non-electronic systems were used to gauge location and distance. Celestial navigation was commonly used in the earliest times to help ship captains navigate. Up until the 20th century in fact, the term navigation was limited primarily to defining how ships were guided across seas (Johansen, 1999) In contemporary society however electronic navigation now determines where a ship is located using radar and radio waves, via electronic instruments that interpret the directional properties of those waves (Johansen, 1999). Even more relevant, electronic navigation is being used by aircrafts and air control towers to ensure accurate and precision landing, in inclement weather and under tight airport conditions.
Prior to the use of electronic navigation instruments, charts were used to aid sailors traveling across land and sea. Charts were usually crafted from observations of the sun and/or stars; they took into consideration the distance of a foreign land based on the time it took to cover the area (Johansen, 1999). The magnetic compass was later invented, further supporting navigational causes. In addition to use of the compass, early navigators utilized the cross-staff and astrolabe, which were two devices that the ancient Greeks had used to "measure the altitudes of celestial bodies." Many early explorers utilized these devices with some success, although the end results were certainly less perfect than what they might be today. Most navigating captains were able to estimate with fair accuracy their location and proximity to destination at any point in time however with use of these simple materials.
Developments occurred in navigation during the 17th century when mapmaking and other developments were encouraged. Trigonometric calculations followed in the 19th century. Electronic navigation came about during the 20th century, and entails the use of hyperbolic and satellite systems that are used as principal navigational tools (Walls, 1999).
Hyperbolic systems include Decca and Loran, which are used to coordinate transmissions in between two or more stations; the signals form a hyperbola (Walls, 1999). Radio frequency is most commonly used for a variety of functions, and provides fast and efficient means to communicate location and time.
Loran generally uses a 90-11-khz frequency range, and has a range of up to 600M; alternatively Decca uses a 70-130khz frequency and a range up to 400M (Walls, 1999). Loran is basically a radio system that has the ability to calculate the position of an aircraft; it also provides navigation assistance (Nolan, 2004).
In the 1980s a system called the Navstar Global Positioning System was implemented; it enables spacecraft crews the ability to map out and store their projected path on an on board computer system, which then allows members to verify the location of their ship "to within a few feet" (Johansen, 2001). The system also enables accurate assessment of the speed of the ship within a few feet per second (Johansen, 2001).
GPS systems are currently considered the most accurate; currently the FAA and the ICAO have agreed that GPS systems should be the international standard for navigation (Nolan, 2004). These navigation instruments will be commonly used in contemporary navigation. They are used however, only as a means of guiding aircraft that are within one mile of an airport. There are more sensitive instruments that are used in cases of bad weather or for example, for landing. For example, Instrument Landing Systems or (ILS) are used on runways to help aircraft land. The instruments utilize transmitters to guide aircraft to "within.5miles of the runway" (Nolan, 2004).