Group members:Ng Poh Hoong

Santhiya A/P PeremelNadilah Binti Mohd YusoffNorazatul Aini Binti Azhar

Norizan Binti Ibrahim

Introduction:What is Remote Sensing?

"Remote sensing is the science (and to some extent, art) of acquiring information about the Earth's surface without actually being in contact with it. This is done by sensing and recording reflected or emitted energy and processing, analyzing, and applying that information.“

Remote Sensing System

Remote Sensing ProcessA- Energy SourcesB- Radiation & The AtmosphereC-Interaction with the targetD-Recording Energy by the sensorE-Transmision,Reception & ProcessingF-Interpretation & AnalysisG-Application

SensorsA device.Measure a physical quantity and covert it

into a signal which can be read by an observer by an instrument.

For example: Mercury-in-glass thermometer-converts the

measured temperature into expansion.

Types:Active

Energy leading to radiation received comes from an external source, e.g., the Sun

Example: Mobile Satellite Service (MSS) Passive

Energy generated from within the sensor system is beamed outward, and the fraction returned is measured

Example: radar

Types:Imaging

Measures the radiation received from all points in the sensed target, integrates this, and reports the result as an electrical signal strength or some other quantitative attribute, such as radiance.

Types:Non-imaging

The electrons released and captured by the detector.

The electrons are used to excite or ionize a substance like silver (Ag) in film or to drive an image producing device like a TV or computer monitor or a cathode ray tube or oscilloscope or a battery of electronic detectors.

Sensor Examples:

Sensor Operation Principle:The remote sensing apply the EM radiation

for most of its source.That the bulk of the radiation sensed is either

reflected or emitted from the target.The radiation travel through the air and

detected by sensors.

Sensor Operation Principle:Designed to measure photons that

transmitted by the EM radiation.Fundamental principle underlying sensor

operation centres on what happens in a critical component - the detector. 

Explained by concept of the photoelectric effect (Albert Einstein)

Photoelectric Effect:An emission of negative particles (electrons)

when a negatively charged plate of some appropriate light-sensitive material is subjected to a beam of photons.

Electrons can then be made to flow as a current from the plate, are collected, and then counted as a signal.

The magnitude of the electric current produced (number of photoelectrons per unit time) is directly proportional to the light intensity. 

Photoelectric Effect:Changes in the electric current can be used

to measure changes in the photons (numbers; intensity) that strike the plate (detector) during a given time interval.

Kinetic energy of the released photoelectrons varies with frequency (or wavelength) of the impinging radiation.

Different materials undergo photoelectric effect release of electrons over different wavelength intervals.

Sensor Classes:

Sensor Classes:Polarimeter

An instrument used in polarimetry which uses two Nicol prisms, one fixed (the polarizer) and one rotatable (the analyzer), with the sample between them, to measure optical activity and other aspects of polarization.

Mechanism of polarimeter: The plane of polarization of the sodium light from the

polarizer is rotated as it passes through a solution of optically active substances such as sucrose.

The extent of the rotation is determined by rotating the analyzer until no light reaches the observer.

The slits in the analyzer are then at right angles to the final plane of polarization 

Sensor Classes:Polarimeter:

Sensor classes:Scatterometer

Satellite remote sensor.Active microwave sensorsDetermine the wind direction over water.Send out a signal and measure how much of

that signal returns after interacting with the target.

The fraction of energy returned to the satellite (backscatter) is a function of wind speed and wind direction. 

Sensor Classes:Radiometer

Instrument that quantitatively measures the EM radiation in some interval of the EM spectrum.

SpectrometerInstrument used to measure properties

of light over a specific portion of the electromagnetic spectrum.

Spectro-radiometerSensors that collect the dispersed radiation in

bands rather than discrete wavelengths. 

Active sensor:Sensor that able to direct energy at an object

in the form of electromagnetic radiation (EMR). 

Object is scanned and the sensors detect any radiation reflected back from the object.

Types of active remote sensing:Active Optical Remote SensingActive Thermal Remote SensingActive Microwave Remote Sensing

Active Optical Remote SensingActive optical remote sensing involves using

a laser beam upon a remote target to illuminate it, analyzing the reflected or backscattered radiation in order to acquire certain properties about the target.

The velocity, location, temperature and material composition of a distant target can be determined using this method.

Example:LIDAR( Light Detection and Ranging)

Active Optical Remote Sensing• LIDAR( Light Detection and Ranging) The instrument works by using a transmitter and

a receiver.  The laser generates pulses which excite the

specified target, causing it to absorb radiation at certain wavelengths.

The target then reflects radiation in the form of photons which are detected by the LIDAR's sensors and converted to an electrical signal.

Active Thermal Remote SensingThermal remote sensing deals with

information acquired primarily in the thermal infrared range. 

The majority of the thermal remote sensing is done using passive sensors.

Active Microwave Remote SensingActive microwave remote sensing uses

sensors that operate in the microwave region of the electromagnetic spectrum.

Example:RADAR (Radio detection and ranging)

Active Microwave Remote SensingRADAR

The sensor transmits a microwave (radio) signal upon a specified target. 

The reflected or backscattered radiation from the target is then detected by the active sensors which measure the round trip time delay to targets allowing the system to calculate the distance of the target from the sensors.

Passive Sensor:Passive sensors detect electromagnetic

radiation emitted from an object. Record incoming radiation that has been

scattered, absorbed and transmitted from the Earth in transit from its original source, the Sun.

Passive Sensor:Gamma-ray spectrometer

Passive sensor that detects gamma rays.The sources for the radiation is are generally

upper-soil layers as well as rock layers. Caused by radioactive decay.  Used to explore mineral deposits.

Passive Sensor:Aerial cameras

Used in aerial photography.Aircraft serve as a platform as well as many

low-earth orbiting satellites deploy many aerial cameras.

Used for topographic mapping.

Passive Sensor:Thermal infrared video cameras

Equipped to detect radiation in the near-infrared range.

Sometimes combined with active sensors, such as radar, to provide additional information.

Aircraft as well as satellites can serve as platforms.

Passive Sensor:Multispectral scanner 

Records information in the visible and infrared spectrum.

Scans the Earth's surface for various wavelength bands.

Satellites act as platforms for such passive sensors.

Used for geological purposes.

Passive Sensor:Imaging Spectrometer

Similar to the multispectral scanner.Scans very narrow wavelength bands of the

spectrum.Satellites are used as platforms.Used for determining the mineral composition

of the Earth's surface and concentrations of suspended matter in surface water.

Platform:The vehicles or carriers for remote sensors

are called the platforms.Selection of a platform is determined by the

altitude that determines the ground resolution.

3 types of platform:Ground Based PlatformsAirborne PlatformsSpaceborne Platforms

Ground Based Platform:Used to record detailed information about

the surface which is compared with information collected from aircraft or satellite sensors.

Placed on a ladder, scaffolding, tall building, cherry-picker, crane, etc.

Up to 50 m from earth.Example:

DOE ARM (Atmospheric radiation Program)NASA AERONET (AErosol Robotic NETwork)

Are primarily stable wing aircraft, although helicopters are occasionally used.

Used to collect very detailed images and facilitate the collection of data.

Up to 50 km from earth.Examples:

NCAR, NOAA, and NASA research aircrafts.

Spaceborne Platforms:Platforms that located from about 100 km to

36000 km from earth.Examples:

rockets, satellites, shuttleTypes of spaceborne platforms:

Space shuttle: 250-300 km Space station: 300-400 km Low-level satellites: 700-1500 km High-level satellites: about 36000 km