Fundamentals of Remote Sensing

Prof. Dr. Sajid Rashid Ahmad

sajidpu@yahoo.com

Atiqa Ijaz Khan _ Demonstrator

atiqa_ss09@yahoo.com

• What is Remote Sensing?

• If you are reading this sentence, now you are doing Remote Sensing. In fact, anyinformation acquired from the object without touching is Remote Sensing.

• Remote sensing offers the ability to observe and collect data for large areas relativelyquickly, and is an important source of data for GIS. (Source: digimap)

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Remote Sensing

• “The art and science of obtaining information about an object withoutbeing in direct contact with the object” (Jensen 2000).

• The science (and art) of acquiring information about an object, withoutentering in contact with it, by sensing and recording reflected oremitted energy and processing, analyzing, and applying thatinformation.• Information usually gathered from spacecraft or an airplane.

• In from of aerial photographs to satellite images.

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Eyes

Binoculars Digital Camera

Pigeon Cameras

1903

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5Types

Terrestrial RS

Optical 300nm – 3000nm

Thermal>3000nm-14,000nm

Microwave 1mm-1mCelestial RS

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HUMAN’s EYE

Rods (to see objects at night) = 7 million

Cones (to see colors) = 100 millionCAT’s EYE

Rods (to see objects at night) =~ 21 million

Cones (to see colors) =~ far less

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The basic principle of remote sensing is based upon the interaction ofelectromagnetic radiation with atmosphere and the earth. Electromagneticradiation reflected or emitted from an object is the usual source of remotesensing data.

Monday, March 30, 2015Institute of Geology, University of the Punjab

8Remote sensing is

concerned with the

measurement of EMR

returned by the earth’s

natural and cultural

features that first receive

energy from the sun or an

artificial source such as a

radar transmitter.

Visible light contains light

from 0.4 to 0.7 micrometers

Infrared light from 0.1

micrometers to 1 millimeter

Wavelength

Frequency

(how many times peak

passes per second)

Light - can be thought of as a wave in the 'electromagnetic field' of the universe

A wave can be characterized by its wavelength or its frequency

Blue green yellow red

1020 Hz 1018 Hz 1016 Hz 1014 Hz 1012 Hz 1010 Hz

1 pm 10pm 10 nm 1 micron 100 microns 1 mm 100 mm

vi-si-ble

Gamma Rays

X-Rays UV N. IR

Th.IR

Microwaves

Radar

TV FMRadiowaves

0.4 m 0.5 m 0.6 m 0.7 m

MidIR

Far IR

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Types of Remote Sensing

Passive Remote Sensing and Active Remote Sensing

Active Remote SensingPassive Remote Sensing

Remote sensing methods that provide

their own source of electromagneticRemote sensing of energy naturally

reflected or radiated from the terrain.

radiation to illuminate the terrain.

Radar is one example.

Own energy source

© 2008 Ko Ko Lwin

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Components in Remote Sensing

Platform

The vehicle which carries a sensor. i.e. satellite, aircraft, balloon, etc...

Sensors

Device that receives electromagnetic radiation and converts it into a signal that can be

recorded and displayed as either numerical data or an image.

One platform can carry more than

one sensor. For example:Platform

Sensor

Platform Name Sensor Name

Landsat TM Thematic Mapper(Passive: Optical sensor)

Landsat ETM Enhanced Thematic Mapper(Passive: Optical sensor)

ALOS PRISM (Passive: Optical sensor) AVNIR-2 (Passive: Optical sensor) PALSAR (Active: Microwave sensor)

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Remote Sensing and GIS Work Flow

Platform (satellite) DATA ACQUISITION

Data transmission

Ground receiving station &

data warehouseSun

Solar radiation from

the sun

Earth

1Example in optical Remote Sensing

DATA PROCESSING & ANALYSIS DATA PRE-PROCESSING

Atmospheric correction

Radiometric correction

Geometric correction

etc.Spatial data modeling along

with other GIS datasetAlgorithm development

Multi-spectral classification 23

© 2008 Ko Ko Lwin

Monday, March 30, 2015Institute of Geology, University of the Punjab

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Examples

Landsat TM/ETMSPOT

ALOS

IKONOS

QuickBird

Earth rotation

Satellite orbit

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14Resolutions

SPATIAL

Smallest identifiable area as a discrete object in an image

SPECTRAL

No. of frequencies recorded = sensors

TEMPORAL

Time interval between measurements

RADIOMETRIC

Intensities identified by sensors

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No.Satellites

Altitude

(km)Bands (µm) Multi-spectral (m)

Panchromati

c (m)

Thermal

(m)Purpose

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Imagery and their price ranges

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18Imagery free of cost

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