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8082958
3l Satellite communications systems
Descrição
A level, A2 IT (Chapter 3) Mapa Mental sobre 3l Satellite communications systems, criado por Gladys Mba em 13-03-2017.
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ict
it
alevel
a2
g063
ocr
chapter 3
it
chapter 3
a level, a2
Mapa Mental por
Gladys Mba
, atualizado more than 1 year ago
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Criado por
Gladys Mba
mais de 7 anos atrás
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Resumo de Recurso
3l Satellite communications systems
GPS
Applications
SatNav
Offers maps, directions and warnings ETC
GeoCaching
GeoTagging
How it works
24 satellites in NAVSTAR constellation.
Always at least 4 satellites in line of sight
Uses 3 satellites to do trilateration, using distance from each station
Orbit earth twice a year
Advantages
O- No need for large maps
O- Time saved planning journeys
O- Calculates new route if error is made
O- very accurate (as good as +- 30cm)
O- Maps can be updated via internet
O- GPS on phone can be used to find lost people
Disadvantages
X- Blind-spots due to tunnels or building
X- Maps may not up-to-date
X- Atmospheric conditions can affect accuracy of GPS
X- Drivers may become lost if GPS breaksdown
X- Desired destination may not be recognised
X- Setting destination and looking at SatNav may distract from driving
Weather
Applications
Monitor cloud formations to predict direction of weather fronts
Collect data on snow ad ice cover, pollution effects, fires, smog, dust and ocean currents
How it works
Can have geostationary orbit 35,000 km over one spot on the equator
Used by TV companies to provide cloud formation photos
Polar orbit, orbits over the poles 850km above earth
Higher quality pictures
Can use thermal and infrared images to find land and water temperatures
Advantages
O- Can monitor fires, hurricanes and sand clouds to give warnings
O- Can track energy usage and light pollution
Disadvantages
X- Expensive to build and launch satellites
X- Weather forecasts may not always be accurate
X- Concern over use of equipment for spying
Television
Applications
Can watch more channels than with aerial due to high bandwidth
Can be free to air or subscription
Can be used with set top box to see TV guide
How it works
TV companies send signals fro earth to a geosychronous satellite
Direct Broadcast satellite (DBS) encrypt signal so homes can only receive channels they have paid for
Signal compressed so more channels can be broadcast with same frequency
Satellite dish receives microwave signals from space
Receicer, set top box, decodes and decrypts signals to receive subscribed channels and decompress signal to find individual channel
Advantages
O- High bandwidth=> Hundreds of channels available
O- Can be received in remote areas where antenna signal is weak
O- Encrypted signals so viewers can pay for one-off programmes or subscriptins
Disadvantages
X- Equipment/ subscription is initially expensive
X- Need extra set top boxes to have satellite TV in other rooms
X- Weather conditions affects satellite signal
X- Signal dish is unsightly
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