Global Positioning System Research Paper

1. Origins And Instances

Over the years the need to answer these questions has been the driving force behind the development of many civil and military applications. During World War Two, one of the nations in combat realized that, even if they managed to build warships relatively rapidly, it was much more difficult to find suitable commanders for the ships. Such positions required candidates with a high level of experience, especially for mapping the ship’s course. From this dilemma LORAN (Long-range Radio Navigation) was born, a system essentially for use at sea, based on the reception and phase difference of radio waves transmitted from two antennae. These two stations transmitted a continual flow of coordinates to navigators equipped with the correct passive antenna, which they then used to pinpoint their exact location on the earth’s surface. This facilitated the commander’s decision-making enormously, as he knew the ship’s position at any time and, by using additional electronic aids or by simply mapping the points already crossed on a nautical chart, he also knew exactly where the ship was headed. The GPS (Global Positioning System) was the natural evolution of LORAN.

At any given moment and point in the area covered by the system, GPS is capable of providing the three-dimensional coordinates (x, y, z, or latitude, longitude and height). Rapid progress in electronic component design, has miniaturized GPS equipment to the extent that even watches and telephones can contain GPS and can provide the wearer with their exact position, the route they followed, and where they have to go.

On certain commercial flights a screen displays a schematized map of the territory below and, using GPS, a pointer indicates the current position of the airplane, the flight path, and, amongst other information, how much time remains before landing. Passengers draw comfort from knowing where they are and when they will arrive. From the cabin they may be able to use the features mapped on the screen to recognize the physical characteristics of the territory below.

Aside from the passive and temporary use of GPS to determine position, route and destination, the system is also important for activities with long-lasting and consequential effects. The most important example is the use of GPS in cartographic or topographic research, and, by extension, to many forms of inquiry in social science. With GPS, the earth’s surface becomes an enormous digitizer, and any point can be identified instantly by its three-dimensional coordinates and archived in a suitable information system, potentially increasing the intensity of sampling events and objects in space and time by several degrees of magnitude. Such measurements affect research and practice in archaeology, economics, geography, planning, and sociology, as well as in the natural sciences. By determining precise coordinates of points on land/or on the surface of water, GPS makes it possible to update maps by locating physical and social features from which GPS gathers data instantaneously and/or detecting changes that have occurred in reality but have yet to be recorded (e.g., new construction, physical changes in the environment, transient events, or those in constant transformation such as people, vehicles, coastlines, woods, glaciers and so on).

2. The General Principles Of GPS Functioning

GPS receivers use radio waves to determine positional coordinates. The radio waves are emitted by a constellation of orbiting satellites, which function as a reference system for GPS. The constellation consists of 24 satellites, which are located in six orbits, inclined at an angle of approximately 50 degrees, at a height of around 20,000 km. Known as NAVSTAR, the constellation is the property of the US government and is controlled and managed by the Department of Defense. The orbits and the distance between the satellites are organized in such a way that, ideally, every point on the earth’s surface can be seen by at least five satellites at the same time, although this is not always this case in practice. The GPS carries out the triangulation of three satellites visible at the same time above the horizon, measuring the distance that separates it from each of these by calculating the time between each satellite (transmitter) to the GPS itself (receiver) using precise time signals emitted by the satellites. The triangulation allows the GPS to determine the latitude and longitude, though a fourth satellite is also necessary to determine a third coordinate giving the height at which the GPS receiver is located. To measure the time required by the signal to travel the distance from each satellite to the receiver, it is essential to use extremely precise equipment to transmit the signal, to calculate the time lapse, and also to pinpoint with extreme accuracy the position of each satellite in space. To this end each satellite is equipped with an atomic clock and its position is constantly monitored and regulated by a series of earth stations.

It is essential to consider the problem of errors incurred by external agents when dealing with instruments as sophisticated as the GPS. To determine the exact time the signal takes to reach the GPS receiver, it is also necessary to understand all the modifications and distortion the signal may undergo while passing through the ionosphere and the atmosphere. The causes of error and/or the malfunctioning of the system are varied, and can range from atmospheric conditions to the position of the satellite constellation in the sky and their visibility from the receiver. The location of the GPS receiver itself may cause problems. For example the receiver may be unable to detect a satellite if it is located under a canopy of thick vegetation or in a city canyon, where its horizon may be modified by the height of surrounding buildings.

Those managing the system itself may introduce certain deliberate errors. GPS, for example, has been subject to SA (Selective Availability), a randomized error deliberately incurred in the time signal from the satellites to degrade the positional accuracy of the receiver to the order of 10 to 100 meters. Acting on a declaration made in 1996, on May 1, 2000, the President of the USA announced the end to the use of SA in GPS, with the immediate effect of increasing and encouraging the use of GPS for civil and commercial purposes throughout the world. In fact, the demand for GPS precision was such that, as soon as the system was recognized by civilian users as being of major importance, they also wanted instruments of reduced size and low cost to have the same excellent functionality found in the military. While knowing one’s position with reasonable approximation (within tens of meters, or at least under 100 m) is satisfactory for most marine or aerial navigation purposes, this level of approximation is not acceptable in other contexts. In an urban situation for example, the user may wish to know what side of the road he is on or which traffic lane to be in, and in the development of technical charts, cadastres, and engineering plans, the precise coordinates of the point on the ground are needed in order to represent it on a topographic map. In the latter case it is necessary to reduce approximation to within a few decimeters or centimeters. In reality, GPS is capable of reaching precision of less than a millimeter, if certain components of the technology are exploited and if the period of observation can be maintained for a sufficient length of time.

The precision of GPS measurements is also influenced by factors such as whether the station is mobile or fixed (at least for the time being) and whether the receiving station functions alone or in connection with other stations. The ability for a station to operate in conjunction with at least one other fixed station provides optimal precision. This technique is called Differential GPS and it is based on the registration of signals transmitted by the satellites and simultaneously picked up by a fixed or base station (Master), of which the precise geographical coordinates are known, and by a mobile station (Rover), located anywhere within a range of around 150 km from the Master station. Post processing the data eliminates the errors in reception by the Rover. The precision of the GPS in the Rover station is able to satisfy all the requirements of civil use from cartographic applications, to support systems for the management and control of transport fleets, and personal mobility.

The late 1990s have seen an increase in the demand for differential correction and it is now easy to find private and public companies that broadcast the data necessary for differential correction in their zone over the radio waves. Certain GPS models are already equipped to receive such radio signals. In the future GPS will continue to improve, in particular after the announcement by the US military controller of the system, with the launching of new satellites, of which 18 are planned in the near future, and with the refinement of certain technical characteristics. The future will also probably see full integration with the Russian-developed GNSS system, which is already integrated with GPS in certain commercial devices.

3. The Relationship Between GPS And Information Systems

The most relevant aspect of GPS to the information society in 2001 is the ability to provide the geographical coordinates of any object on the earth’s surface and to increase our knowledge of the object’s characteristics with ancillary data, collected in real time and directly from the field, at very low cost. Without doubt, the geographical component is an essential part of current databases and is generally deduced from a classification of objects by name (city, road, house number, etc.) or is represented by the cartographic coordinates of the single object gathered from maps (for example the centroid of a manhole cover, telephone or electricity pole, the axis of a water or gas pipe). In each case the geographical component, obtained by traditional means, is approximate, expensive, or unreliable in relation to both time and space. Time, because things can change from one moment to the next (an electricity pole can be moved relatively rapidly in reality but not so rapidly on the charts representing it). Space, because an element located in a certain territory undergoes continual transformation, the shores of a lake or a coastline for example can be modified by environmental factors.

Conferring a geographical address on each item of data allows for the application of the analytical, inquiry, and management functions of a geographic information system (GIS). Real time availability of the geographic address means that the spatial analysis can be carried out instantaneously in the field. Typical spatial analysis functions include: investigating relationships of proximity to, or distance from, the object, superimposition of information layers, the search for the shortest or any route that satisfies specific conditions, identification of spatial environments that group objects with specified characteristics, monitoring transformations of the object, and so on. Typical functions of inquiry analysis are those that allow us to understand the information linked to an object by selecting that object from a spatial database rather than selecting an object from the alphanumeric database and obtaining thematic charts ad hoc. Typical functions of information system management are those that permit us to continually update the constituent elements by refreshing the data and integrating the geographic database whenever necessary.

The continual information flux is one of the major problems in information society and updating coordinates in three-dimensional space is even more challenging. Connecting GPS to other techniques helps solve this problem. For example, we can consider digital cartography, necessary for a decision-making process in a territorial or urban context. This is archived in appropriate databases and territorial information systems use it to undertake analysis and to aid in making the above-mentioned decisions. But what happens when digital cartography no longer reflects reality? A city or region can sometimes change very rapidly and if the digital map is not updated, then we run the risk of the information system elaborating data that is no longer. Invalid information may be merely inconvenient or lead to serious social or legal complications. GPS helps greatly, but it is not only maps that need continual updating but also the geographic address of data that is particularly useful in social science. Among these are census tracts, political districts, administrative units, pollution zones, and epidemiological information, or research concerning traffic and movement. More controversially we may monitor individuals.

4. Examples Of The Use Of GPS And Its Social Implications

The development of GPS and its diffusion is a step towards having geographic address (x, y, z coordinates in space, or longitude, latitude and height) and exact time as a component of any type of information. GPS equipment is already widely used by utilities companies for the identification of the components in their networks (poles, pylons, wells, technical components, etc.), while among the earlier applications we should remember the use of GPS for the positioning and identification of submarine oil wells from offshore oil platforms. Additionally anyone, at any moment in time, can visualize the location or destination of any vehicle transmitting its coordinates to be collected in real time by GPS. For example when mounted on a public bus, a GPS can supply immediate information on the vehicle’s location, the journey time and anything else that is necessary to satisfy the needs of the driver, passenger, or manager alike. For some time now, insurance companies have been using this system to reduce the incidence of car thefts. Car manufacturers are now equipping cars across the range with navigators: electronic navigation systems containing a digital map of the area in which the car is travelling and on which the positioning and movement of the vehicle itself is traced, thanks to the continual tracking of its location through GPS. Integrated with other systems, GPS permits a vehicle to proceed automatically, without the aid of the driver or pilot. Systems already exist in marine and aeronautical applications that are capable of functioning as autonomous autopilots. Exact details of military applications are not public knowledge, but it is easy to guess that the same basic technology is used with more sophisticated developments. An internal GPS in a cellular phone provides the user with their exact coordinates, and can be used to visualize the location of similarly equipped phones. Such devices are in regular use at large conventions to facilitate (or avoid) meetings. The same device alerts emergency services to incidents on lonely stretches of unfamiliar road or, worn as clothing, GPS may guide the sight-impaired or proof children against becoming lost. All fields that use geographic coordinates may derive benefits from the use of GPS.

There are two principal problems linked to the use of GPS: a reduction in the capability of orientation and the limitation of privacy.

The problem of the reduction in the capacity to orientate oneself is due in part to the use of digital coordinates, rather than analog information such as: go to the square, turn right at the newsstand, go straight on to the white building, etc. With GPS a person can supply a visitor with the coordinates of their position by simply pressing a button; the visitor receives the coordinates and transfers them to his autopilot or navigation system, and the vehicle navigator directs the visitor to the location they require. Nothing will remain in the visitor’s memory, unless he has paid attention to the features of his route and not simply paid attention to the screen. It is a question of personal choice whether to learn to navigate in one’s environment or to rely wholly on digital assistants.

The privacy problem is a crucial aspect of the use of GPS in society. The power of knowing in a given moment the location of someone equipped with a GPS can be a source of enormous security in certain cases; for example for those suffering from an accident or particular illness who may require treatment as quickly as possible. But knowing someone’s movements is potentially a great intrusion on personal privacy. For example, with GPS and GIS we could discover the shop, office or facility someone is currently visiting, or recreate their activities during the past 24 hours or longer. The surveillant society is the flip-side of the information society. Separating valuable monitoring from unwarranted intrusion into personal privacy, and deciding who has the power to distinguish between them, poses a major problem for society.

5. Summary

Cartographers, engineers, planners, archaeologists, and geographers have drawn enormous advantages from the active use of GPS and will continue to enjoy the benefits of a new technology that allows for rapid and much less costly collection and updating of geographic information. The integration of engineering designs realized with CAD, digital mapping, and GPS, introduces the possibility of devices capable of elaborating designs for civil engineering and proceeding through interactive surveys, to the construction of roads, buildings, etc. GPS also integrates well with the analysis of data that has been collected via satellite for the observation of the earth, in that it allows for the exact identification of the coordinates of specific features on the satellite image. Social applications range across all walks of life. Inevitably, as with all technological innovations, its use should be evaluated critically, and the limits of its appropriate use determined.

Bibliography:

1. http://www.trimble.com/gps
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3. http:/www.navtechgps.com/
4. http://www.colorado.edu/geography/gcraft/notes/gps/gps-f.html