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Satellite Systems

PAST QUESTION: Describe Global Positioning Satellite (GPS) systems and satellite navigation


Global Positioning Satellite (GPS) systems are used to determine the exact location of a number of modes of transport (e.g., airplanes, cars, ships, etc).  Cars usually refer to GPS as satellite navigation systems (i.e. satnav).

Satellites surrounding the Earth transmit signals to the surface.  Computers installed in the mode of transport receive and interpret these signals.  Knowing their position on Earth depends on very accurate timing (atomic clocks are used in the satellites which are accurate within a fraction of a second per day).  Each satellite transmits data indicating its position and time.  The computer on board the mode of transport calculates its exact position based on the information from at least three satellites.

In cars, the onboard computer generally contains stored road maps.  With these satnav systems, the car’s exact location, based on satellite positioning, can be shown on the map and the driver can also be given verbal instructions such as ‘After 200 metres, take the next right turn onto BCD124’.  A screen on the satnav device also shows the car’s position in relation to the road network.



It removes errors (can warn drivers about one way streets, street closures, etc).

The system can also give useful information such as location of restaurants, petrol stations, service areas.

The driver need not consult paper maps, so it is far safer.

The system is able to estimate the time of arrival.

It is also possible to program in the fastest route, route to avoid towns, etc.

The system can warn the driver about the location of speed cameras (again aiding safety).



If incorrect starting point or ending point is keyed in the system, it will give incorrect information.

If the maps are not kept up to date, they can give incorrect instructions.

Loss of satellite signals can cause problems.

Unless the system is sophisticated, road closures, due to accidents or road works, can cause problems.


PAST QUESTION: What is Geographic Information System (GIS)


Geographic Information System (GIS) is a computer system that allows us to map, model, query and analyse large amounts of data according to their location.

GIS allows us to create interactive queries, analyze spatial information (this refers to how objects fit together in space) or edit map data.  The technology combines maps with computer graphics and databases.

Essentially GIS enables the following:

  •     Amalgamation of information into easily understood maps
  • performance of complex analytical calculations and then presentation of the results in the form of maps, tables or graphics (or a combination of all three)
  • geographers, scientists and engineers are able to see the data in several different ways in order to see patterns and relationships.

GIS essentially uses layering techniques to produce a visually effective answer to a query made in the GIS system.

Carrying out queries on GIS systems (in a method similar to internet searches) will produce the data which matches the query.  The data will be displayed in the form of a diagram, map or a set of tables.  By zooming into the map, it is possible to find finer details about the layering data used.


Uses of GIS systems

Teachers can use GIS in their geography, engineering or science classes.

Environmentalists and Biologists use GIS to protect animal and plant life in vulnerable areas (which meet a certain criteria after carrying out a search on the database).

Emergency services use GIS to send the closest emergency personnel to a location.


PAST QUESTION: Describe Media Communication Systems


Communication media refers to methods of delivering and receiving data/information using telecommunications.

There are various media available to send and receive information (e.g., copper cable, fibre optics and Wi-Fi).  However, we will take the example of the global communication method which makes of satellites.

Satellites contain antennas, transponders (to allow receiving and sending of data), solar panels (for power from the Sun) and propulsion (to ensure the satellite is in the correct orbit at all times).

Signals are converted to analogue (if necessary) and then beamed to the satellite from a satellite dish on Earth.  The signals are delivered by carrier waves which consist of radio waves.  Each signal has its own frequency and bandwidth (the larger the bandwidth the more data can be transmitted).

Once the data reaches the satellite, it is then resent to Earth.  The satellite usually ‘boosts’ the signal before sending it back to Earth.  Often the frequency is changed to prevent the signal received being confused with the signal sent.

The satellite system is used to transmit data from one part of the planet to another.  Due to the often great distances, cables would be too costly and there is also the problem of signal deterioration over long distances.

Satellite systems are used to transmit telephone, internet and television data around the world.


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