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Passive and Active sensors
Passive sensors
• Remote sensing systems which measures natural
energy
• Sun provides source of energy for remote sensing
• Energy from sun is either reflected as is the case
for visible wavelengths or absorbed and re-
emitted as it is for infrared wavelength
• Remote sensing systems which measures naturally
available energy are called passive remote sensing
• Passive remote sensing can only take place when sun
is illuminating the earth
• Or no reflected energy available from the sun at night
• Energy which is naturally emitted (infrared) can be
detected day or night provided energy should be
emitted large enough to be recorded
• Passive remote sensing is also possible in microwave
region
Passive and active sensors
Disadvantage
• Passive sensors will work only during the day
time as sun’s reflected energy is not available
for illumination at night
• Seasonal dependency
Active sensors
• Active sensors provides their own energy
source for illumination
• Sensors emits radiations which is directed
towards the target to be investigated
• The radiation reflected from that target is then
detected and measured by the sensors
• Its advantage is that we can obtain
measurements anytime regardless of the time of
the day or season
• Another advantage is that active sensors can be
used for examining wavelengths that are not
sufficiently provided by the sun such as
microwaves
• Active systems require the generation of a
fairly large amount of energy to adequately
illuminate the targets. Example is radar
Passive and active sensors
Passive and active sensors

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Passive and active sensors

  • 2. Passive sensors • Remote sensing systems which measures natural energy • Sun provides source of energy for remote sensing • Energy from sun is either reflected as is the case for visible wavelengths or absorbed and re- emitted as it is for infrared wavelength
  • 3. • Remote sensing systems which measures naturally available energy are called passive remote sensing • Passive remote sensing can only take place when sun is illuminating the earth • Or no reflected energy available from the sun at night
  • 4. • Energy which is naturally emitted (infrared) can be detected day or night provided energy should be emitted large enough to be recorded • Passive remote sensing is also possible in microwave region
  • 6. Disadvantage • Passive sensors will work only during the day time as sun’s reflected energy is not available for illumination at night • Seasonal dependency
  • 7. Active sensors • Active sensors provides their own energy source for illumination • Sensors emits radiations which is directed towards the target to be investigated • The radiation reflected from that target is then detected and measured by the sensors
  • 8. • Its advantage is that we can obtain measurements anytime regardless of the time of the day or season • Another advantage is that active sensors can be used for examining wavelengths that are not sufficiently provided by the sun such as microwaves
  • 9. • Active systems require the generation of a fairly large amount of energy to adequately illuminate the targets. Example is radar