ContentsWhat is Remote Sensing ?What is Satellite Remote Sensing ? What is Earth Observed?Introduction to the basic elements in Remote SensingThe SensorsPassive Sensors &Active SensorsThe PixelThe Spatial Resolution
What is Remote SensingIt is a method of collecting information aboutan object without the instrument being used tocollect the data, coming in direct with the object.In other words it means, ‘measuring at a distance without physical contact’.Like, Eyesight is a form of remote sensing.When we take a photograph of an object, theEMR (Electromagnetic Radiations) is recorded on the film.A scanner in a satellite also records EMR. The picture takenfrom a satellite is referred to as an ‘image’.
What is satellite Remote Sensing? Whatis Earth ObservedThere are a great number of satellites inorbit around the earth. They have designed, built andlaunched in order torelay images of our planet back to earth.(application in areas such as scientificresearch, industry, environment, engineering, urban planning,agriculture, meteorology, education, business, otherareas of people related activities and in policies adopted bygovernment)Remotely sensed information is most widelyused in the application of urban, agriculture,disaster monitoring, oil spill monitoring etc.
Introduction to the basics elements inRemote Sensing The object to be observed The instrument or sensors to observe the target The form of the ‘information’ obtained from remote sensing, and the method of storage A platform to hold the instrument
The SensorsA sensor is a device used to acquire aPhotograph or an image. What a sensorWill do is, it will ‘sense’ and measure theAmount of radiated energy reflectedFrom an object and record it.Although the camera is a type of sensor, the word‘sensor’is normally used for the device used toAcquire images in remote sensingIn satellite remote sensing, the types of sensors used of capturing radiation from many differenet parts of the electromagnetic spectrum, which are visible to the human eye.
Passive Sensors & Active Sensors Passive SensorsAsensors will record information reflected fromEarth surface features.A sensor, which measures wavelengthsReflected or emitted by the objects under observations, is calledA‘ passive sensor’. Active SensorsActivesensors ‘emits’radiation that reflects off objects and only theLittle energy returned to the sensor is measured. The most commonActive sensor used in remote sensing is ‘radar’.
The Pixel A given data set or image, can be represented by a great number of pixel. A pixel is the smallest unit on a satellite image. A pixel is generally equivalent to one word or byte. (sometimes 2 bytes)Displayed in the correct order all the pixels build up a meaningful imageFor examples, if the observed object is a green plant and the sensor is specially made to detect green, the intensity will be very high. If we use the same sensor to observed a red object, the intensity will be very low The value of the pixel varies from 0 to255 displayed on a screen as gray levels ranging from black(0) to white(255)
Spatial Resolution The spatial resolutionor ground of an image isthe smallest size of afeature that the sensoris able identify.