hi...it has been a while that we haven't talked about our beloved topic 'remote sensing' so i thought its the time to do the otherwise.
today let us talk about sensors for a start.
in the dictionary the word 'sensor' is defined as a device which detects or measures a physical property.
well of course it is true that in the journey of our lives from birth to death we use so many sensors in order to interact with the world.in my case the world is what i have sensed through my sensors.
eyes,ears,skin,tongue,nose they all acted as sensors (but not all as remote sensors). in remote sensing we consider about the sensors which don't require a physical contact with the object being measured or detected.
the most significant sensor for me is the "EYE" it is the fundamental remote sensor of the human body.
just take a look at the human eye .
similar kind of thing happens with the sensor of a remote sensing platform.now for an eye to get info about an object light must enter through the cornea.but we all know that the source of the light which enters the eye reflecting off an object is not the eye itself, no wonder why we dont see people with flash bulb eyes lol... so human eye is what we call a "passive sensor"
passive sensors need a source to illuminate the object being observed and that source is not embedded to the sensor.(as in Landsat )
so the active sensors are the opposite of the passive ones they have got their own source of electro-magnetic radiation emitter.(as in SONAR,LIDAR)