Lecture-8 Remote Sensing

Remote Sensing

Contents Definition

Types of Remote Sensing

Elements involved in Remote Sensing

Process of Remote Sensing

Sensors

Usual Platforms

Interaction with Atmosphere

Remote Sensing & GIS

Aerial Remote Sensing

Image Processing in Remote Sensing

Types of Resolution

Correction

Advantages & Disadvantages of Remote Sensing

Applications

Conclusion

DEFINITION

It is the acquisition of information about an object orphenomenon without making physical contact with the object

In modern usage, the term generally refers to the use of aerialsensor technologies to detect and classify objects on Earth bymeans of propagated signals

TYPES (on basis of energy)

Active Remote Sensing (artificial energy source)

Passive Remote Sensing (natural energy source)

TYPES (on basis of range of electromagnetic radiation)

Optical Remote Sensing(wavelength range 300nm-3000nm)

Thermal Remote Sensing(wavelength range 3000-14000nm)

Microwave Remote Sensing(wavelength range 1mm-1m)

ELEMENTS INVOLVED IN REMOTE SENSING

Source of energy

Radiation and the atmosphere

Interaction with object

Recording of energy by sensor

Transmission, reception and processing

Interpretation and analysis

Application

PROCESS OF REMOTE SENSING

Data acquisition

Processing

Analysis

Accuracy assessment

Information distribution to users

SENSORS

Imaging Sensors

Sensors which provide output to create image

Example: LISS I, LISS II, LISS III, etc (Linear Imaging Self Scanning Sensor LISS)

Non-imaging Sensors

Sensors which provide numerical output with respect to quantum of radiation

Example: Radiometer, Scatterometer, etc

USUAL PLATFORMSAIRCRAFT

Helicopters

Microlites

Low altitude aircrafts

High altitude aircrafts

SATELLITE

Orbiting satellites

Geostationary satellites

INTERACTION WITH THE ATMOSPHERE

Radiation used for remote sensing has to travel through Earth’s atmosphere

Particles and gases in the atmosphere can affect it

These effects are caused by mechanisms of scattering and absorption

Remote Sensing & GIS The science of acquiring information about the Earth using remote

instruments, such as satellites

It is inherently useful for disaster management

Satellites offer accurate, frequent and almost instantaneous dataover large areas anywhere in the world

When a disaster strikes, remote sensing is often the only way toview what is happening on the ground

Remote Sensing & GIS (Contd..)

Energy Source or Illumination (A)Radiation and the Atmosphere (B) Interaction with the Target (C)Recording of Energy by the Sensor (D)Transmission, Reception, and Processing (E)Interpretation and Analysis (F)Application (G)

Aerial Remote SensingAerial Remote Sensing Aerial photography is the most commonlyused form of remote sensing and is widely used for topographicmapping, surveys for geological, soil and forestry mapping,engineering, town planning and environmental surveys on largerscale

IMAGE PROCESSING IN REMOTE SENSING

Input data

Reconstruction/ correction

Transformation

Classification

Output

TYPES OF RESOLUTION

Spatial Resolution

The size of a pixel that is recorded in a raster image

Spectral Resolution

The wavelength width of the different frequency bands recorded

Radiometric Resolution

The number of different intensities of radiation the sensor is able to distinguish

Temporal Resolution

The frequency of flyovers by the satellite or plane

CORRECTION

Radiometric correction

Gives a scale to the pixel values

Topographic correction

In rugged mountains, as a result of terrain, the effective illumination of pixels varies considerably. The purpose of topographic correction is to eliminate this effect

Atmospheric correction

Elimination of atmospheric haze by rescaling each frequency band

ADVANTAGES OF REMOTE SENSING Real time

Spatial locations and extent of features can be corrected accurately

Cheaper

Faster

Different scales

Easy updation

More analytical themes

Remote sensors "see" over a broader portion of the spectrum than the human eye

DISADVANTAGES OF REMOTE SENSING Expensive to build and operate

Measurement uncertainty can be large

Data interpretation can be difficult

APPLICATIONS OF REMOTE SENSING Conventional radar is mostly associated with aerial traffic control,

early warning, and certain large scale meteorological data

Altimeters measure wind speeds and direction, and surface ocean currents and directions

Light detection and ranging (LIDAR) is well known in examples of weapon ranging, laser illuminated homing of projectiles

Radiometers and photometers are the most common instrument in use, collecting reflected and emitted radiation in a wide range of frequencies

RADAR LIDAR

APPLICATIONS OF REMOTE SENSING (Contd..) Stereographic pairs of aerial photographs have often been used to

make topographic maps

Hyperspectral imagers are used in various applications including mineralogy, biology, defense, and environmental measurements

remote sensing allows to follow-up and monitor risk areas in the long term, to determine desertification factors

Conclusion Remote Sensing and GIS technology is very effective tool for

suggesting action plans /management strategies for variousdisciplines

The technique of obtaining information about objects through theanalysis of data collected by special instruments that are not inphysical contact with the objects of investigation