This paper will analyze the management information system concept which is the Global Positioning System users. We will define what is the concept is, including its background and how it works. There will be a brief analysis of a company in Swaziland that is involved in this concept. We will explain the drawbacks faced by the users of the concept in Swaziland.
GLOBAL POSITIONING SYSTEM BACKGROUND (G.P.S)
According to Wikipedia Encyclopedia, G.P.S is a satellite based positioning service that is free to use by any user. The system is owned by the UNITED STATES GORVERNMENT and operated by DEPARTMENT OF DEFENCE .The G.P.S is a U.S. space based radio navigation system that provides reliable positioning navigation and timing services to civilians on war on continuous worldwide bases freely available to all. The global positioning system was intended for military application but in the 1980s the government made the system available for civilian use. It started in 1960 with the launch of the first satellite navigation system called TRANSIT it had five satellites. In 1967 another system called TIMATION was developed which was more accurate than the first one. Since then a series of systems have been developed but mainly for military navigation purposes only until 1983, the U.S president Ronald Reagan issued a directive (order) making G.P.S freely available for civilian use. After that, noticeable in aviation G.P.S become widely used and developed but only a few company could access it since it was given on selective availability bases which meant only a few U.S companies could have access to it. In May 2000 the selective availability was discontinued.
THE GPS BASIC CONCEPT AND HOW IT WORKS
The geographic positioning system (GPS) is made up of at least three parts which are a network of 32 satellites but only 24 are operating with the other three in standby if one breaks down, stations on Earth which monitors and control the satellites which means that they are used to exactly track each satellites orbit, and GPS receivers which are owned by the users of GPS. The 24 GPS satellites orbit around the globe approximately 19000km above sea level and they orbit around the globe twice a day in a precise circling manner at about 11000km/h. If a person wants to use the GPS he must have a GPS receiver insight of at least three satellites to calculate a 2D position. A 2D position will tell you the latitude and longitude of your position and time. But with at least 4 or more satellites in view of the GPS receiver the satellites will calculate a 3D position, which tell you about the latitude, altitude, longitude and time.
What is important to note is that the GPS receiver does not transmit data but only continuously receive satellites signals, the GPS satellites transmits the radio-wave signals, the signal can pass through clouds, glass and plastic but cannot pass through solid objects. Once the GPS has identified the GPS receiver's position on earth then the GPS satellites will calculate the distance, speed, bearings and time for sunrise and sunset. With the 24 satellites orbiting around the globe at the same time but different speed means that at least 12 satellites will be in view of a GPS receiver on earth. The satellites will endlessly transmit information which will include, ephemeris data which are parameters that may be used to correctly calculate the location of each satellite at a particular point in time by showing the path the satellite is following as it orbits around the Earth, almanac data used to forecast which satellites are closer when they are looking for each GPS signal and the time the message was sent. When the GPS receiver has sent the information to the nearest GPS satellites it will use a process of trilateration to calculate the users' location and rely on the atomic clocks on board for very accurate time reference.
Trilateration is the way GPS receiver measure the time it takes the satellite signal to reach the receiver and the length of the GPS signal which is electromagnetic waves that travel at light speed of nearly 300 000 km per second. The process is sustained by finding the intersection of three or more imaginary spheres surfaces with given centers and radii of the spheres which will then give the distance from each satellite to where the receiver is. All the satellites are synchronized to transmit timely at the same instant but arrive at the GPS receiver at slightly different times as the satellites are not situated at same distance and if you are further away from the satellites it might take sometime than if you are close. The distances from three satellites will probably intersect at two points and one of these points will be on the earth surface but with four or more GPS satellites the spheres will intersect at just one point so as to pinpoint the accurate current location of the designated place. The GPS receiver will measure the data received against the information contained in its orbit to determine the distance from the given satellite. The GPS receiver can automatically change the size of the spheres until the intersection point is located, obviously if the size of one sphere is calculated then the other spheres should be adjusted with the same distance. The receiver is located where the spheres will intersect and fortunately most of the GPS gadgets are user friendly which makes it easier to figure out what you need. The GPS uses the carrier-phase GPS frequency to make a perfect timing than the code-phase GPS frequency; the problem with the code-phase GPS is that in the speed of light it commits errors of at least 3-6 meters. The receivers have a basic accuracy of about 10 meters.
With Wide Area Differential GPS improves the accuracy of GPS location. WADGPS are geostationary satellites which use fixed mounted receivers around the Earth. They measure the difference between their actual known position and the calculated GPS position. The GPS instead of transmitting signal straight to the GPS receiver it goes via the DGPS stationary satellites. The WADGPS with more than 25 ground stations communicate errors back to the wide area main station, then the main station applies corrections to the original data and sends the corrections to a geosynchronous satellite, it improves to less than 3 times accuracy. In order to get the corrected signal the GPS receiver must have a differential beacon receiver and beacon antenna in addition to their GPS.A Company Using G.P.S
We were able to identify Airfix navigation as a company using G.P.S in Swaziland which is situated in Matsapha Airport which deals with flight learning, i.e. training pilots, aircraft maintenance and repair, and aviation services. According to Mr. Neville (Airfix, Operations manger) Aviation GPS Navigation means knowing where you are, where you want to go, and having a good idea of how much time and fuel it will take to get there. Navigation means finding your way. Aviation navigation is based on G.P.S which is a means of navigation, the system based on satellites which are continuous surrounding the earth. The G.P.S receiver in the aircraft finds the nearest two satellite signal in the distance to the station and also the time it will take to reach the destination. This is possible because the G.P.S receiver continuously shows the map as he travels. The process of acquisition also tells the time it takes for the signal to travel creates a precise triangle between the signal two satellites and the aircraft, telling the pilot his latitudes and longitudes within one meter or a little more than one yard. This also helps the pilot to know his altitude height above sea level.Airfix uses GPS in providing the following services:
To determine location either of the plane or airport, pilots at Airfix aviation uses G.P.S receivers. The G.P.S receivers provide the pilots with information about the position the plane is at that moment, and then it will help locate the nearest airport. G.P.S can then calculate the distance from the plane to the airport as well as the time it will take to reach that airport. This helps the pilots knows if the plane has enough fuel to reach that destination.Navigations
Airfix uses the G.P.S concept when training pilots. During pilot flight planning, GPS navigation is used in the aeronautical charts. Small electronic G.P.S receivers inside the plane are used to determine the planes location (longitude, latitude, and altitude) to within a few meters using time signals transmitted by G.P.S satellites. Early pilots during flight planning they had to obtain SKUK codes from different airports that are within his/her route, this provided them with a zigzag path that the pilots will to follow, they do not have to use that now because of the G.P.S technology. The precise point-to-point navigation of a GPS system helps save fuel and extends the aircraft's range by ensuring pilots stay on the most direct routes to their destination.Timing
G.P.S receiver is able to time the pilot as to the speed the plane is flying in every distance, the height above sea level and as well the degrees it should take as it approaches a turn. However it also gives the pilot the height it should direct the plane in certain location since some of the places the plane is expected to pass through are mountainous and have different altitude.Drawbacks
- Lack of reliable power supply
- Requires Software upgrade
- May not user friendly
- Lack of accuracy
Since most of receivers uses rechargeable batteries which when they lack power the G.P.S does not work and hence the G.P.S receiver becomes useless to the user.
The GPs receivers have software packages that are designed to work on different hemispheres i.e. Southern & Northern hemisphere. This requires the user to change or upgrade the software package when crossing or interchanging hemispheres.
The devices may not be easy to use amongst users. It requires a certain level of technological literacy and map reading is essential.
It must be taken into consideration that the accuracy of the trilateration process heavily depend on the distribution of the GPS satellites around the Earth. If they are distributed evenly, the person who is using the GPS receiver will get an accurate position but if all the satellites orbit close together the GPS receiver cannot get an accurate position. Sometimes a bad signal which can be caused by tall buildings or bushveld may reduce the accuracy of the GPS and these disturbers are called dilution of precision. Fortunately the receiver will alert the user if there is such a situation.
G.P.S is still a growing concept in Swaziland which is primarily used for aviation which includes navigation, timing and location .with the growing technology there are a lot of experiments in process which will increase the use of G.P.S in aviation, and also used in car tracking and location of places.
- Botha Lucas, operations managers, Unitrans Swaziland
- Neville, Managing Director Air Fix Aviations
- Wikipedia encyclopedia http://en.wikipedia.org/ free encyclopedia
- http: // en.wikivarsity.org/
- Richard Langley column "Innovation" GPS World magazine. Questex maedia group Inc. 2009
- Operations Manager, Tracker Swaziland