Finding the way from one place to another is called NAVIGATION. Moving of an aircraft from one point to another is the most important part for any kind of mission. Navigation used to depend on observation, using simple maps and geometrical instruments for calculations. Today, aerial navigation has become an art which nears to perfection. Both external Nav-aids (Navigational Aids) and on-board systems help navigate any aircraft over thousand of miles with such accuracy that could only be imagined a few decades ago.
Inertial Navigation Systems (INS) are self-contained systems that operate autonomously and provide reliable and accurate platform attitude, position, and velocity information regardless of weather or electronic warfare. They are capable of worldwide operation over a wide range of velocities, attitudes, and accelerations. After initialization using known position and velocity, an inertial system provides continuous estimates of position, velocity, and attitude. Since the jet era began, continuous improvements have been made in navigation systems making flying increasingly safer.
Both commercial and military planes have expanded radar coverage and high-tech devices to warn pilots of wind-shear conditions, nearby aircraft and proximity to the ground or mountains (for example, “EGPWS”-early ground proximity warning system, as used on the B747ER). GPS (Global Positioning System) is the only system today able to show you your exact position on the earth at anytime and any weather condition. 24 satellites are all orbit around the earth at 11,000 nautical miles or approximately 20,200km above the earth. The satellites are placed into six different orbital planes and 55 degree inclination.
They are continuously monitored by ground stations located worldwide. Thus GPS serves as a navigational aid for aircrafts when flying in any weather conditions. As an aircraft is flying, the GPS receiver continuously calculates the current position and displays the correct position. The GPS unit takes note to the satellite’s signal and measures the time between the satellites transmission and reception of the signal. By the process of triangulation among the several satellites being received, the unit computes the location of the GPS receiver.
GPS receiver has to see at least four satellites to compute a three dimensional position (it can compute position with only three satellites if know altitude). No frequency tuning is required, as the frequency of the satellite transmissions are already known by the receiver. GPS receivers have been basic equipment in all B747 airplanes for several years. In places with little or no ground-based navigation, GPS allows aircraft to navigate using satellites. GPS systems are also installed on the F16 fighter jets, to perform in extreme difficult conditions, where the enemy tries to confuse the pilot.
However, the GPS Embedded Module system, GEM has been developed by the government to produce a system that is not only capable of navigation as the in the case of the commercial jet, but one in which is technically advanced to perform under any circumstance. GEM receivers offer superior position finding, velocity and time accuracy over the full range of dynamics encountered in airborne and other applications. GEM V represents the importance of updating GPS receiver applications to make sure the F16 fulfils its role in sky. GEM V provides state-of the art secure GPS solutions for the F16 jet.