Cl-1&2 RS Introduction

8/2/2019 Cl-1&2 RS Introduction

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CS5905 Spatial Informatics

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Remote Sensing

Lecture 1 & 2: Introduction to RS

Dr. K. S. RajanAssociate Professor,

Lab for Spatial Informatics, IIIT Hyderabad

Dec 29th 2011, Jan 2nd 2012


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A Picture is worth a thousand

words (Chinese Proverb)

What is this?What do you

think of this

statue?


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A Satellite Image- IRS P6 image of the West Coast of India


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Remote sensing began in 1840

when balloonists used new

camera technology to take

pictures.

At the turn of the century there

was a pigeon fleet in Europe.

Camera systems were placed on

V-2 rockets tested at White Sands,NM after WW II.

Sputnik in 1957 changed our

outlook toward using outer space

as a place from which observe the

earth.

Explorer-1 was the first successfulU.S. earth satellite launched onJanuary 31, 1958 (123 days after

Sputnik-1) TIROS-1 (Television InfraredObservation Satellite) was the firstweather satellite launched on April1, 1960

TIROS 1 paved the way forgenerations of weather satellites.

Explorer-1

TIROS-1

Stark contrast between first TIROS image and the full-color

full-Earth image that GOES-8 produces today.


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What is remote sensing?Definition 1 Remote sensing is the acquiring of

information about an object or scene withouttouching it through using electromagneticenergy

a. RS deals with systems whose data can be usedto recreate images

b. RS deals with detection of the atmosphere,oceans, or land surface


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Basic Remote Sensing System


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Elements of a Remote Sensing

System


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What is Remote Sensing

Definition 2 Remote sensing is the non-

contact recording of information from the

UV, visible, IR, and microwave regions of

the EM spectrum by means of a variety of

electro-optical systems, and the

generation and delivery of informationproducts based on the processing of these

data


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The Remote Sensing Process


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The Remote Sensing Process Energy Source or Illumination (A) - the first

requirement for remote sensing is to have anenergy source which illuminates or provideselectromagnetic energy to the target ofinterest.

Radiation and the Atmosphere (B) - as theenergy travels from its source to the target, itwill come in contact with and interact withthe atmosphere it passes through. Thisinteraction may take place a second time asthe energy travels from the target to thesensor.


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The electromagnetic (EM) spectrum


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EM Spectrum Regions Used in

Remote Sensing

1. Ultraviolet ( < 0.4 m)

2. Visible ( 0.4 m < < 0.7 m)

3. Reflected IR ( 0.7 m < < 2.8 m)

4. Emitted (thermal) IR ( 2.4 m < < 20 m)

5. Microwave ( 1 cm < < 1 m)

= EM radiation

wavelength


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Ultraviolet Radiation

Shortest wavelengths

used for remote

sensing

Some earth rocks and

minerals fluoresce

when illuminated with

ultraviolet light


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Visible Light Region of EM Spectrum

Detected by our onboard remote sensor (eyes)

A very small part of the total spectrum

Ranges from 0.4 m, violet, to 0.7 m, red


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Thermal IR Sensors

Ranges from 0.7 to 100 m

Reflected IR covers wavelengths approximately 0.7 m

to 3.0 m Thermal IR deals with the Far IR region of the EMspectrum, wavelengths between 2.4 and 100 m

Most Thermal IR scanners use wavelengths between 8and 15 m


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Microwave Spectrum

From about 1 m

to 1 m wavelengths

Short wavelengths

similar to thermal

Long wavelengths

similar to radio

waves


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Microwave remote sensing instrumentsoperate at wavelengths greater than 1 mm


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Interaction with the Target (C) once theenergy makes its way to the target through the

atmosphere, it interacts with the target

depending on the properties of both the target

and the radiation.

Recording of Energy by the Sensor (D) - after

the energy has been scattered by, or emitted

from the target, we require a sensor (remote -

not in contact with the target) to collect and

record the electromagnetic radiation.


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Surface Interactions

Absorption

Reflection

Specular Diffuse

Transmission


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Spectral Response

Spectralresponsepatterns allowfordifferentiationof varioussurfaces

May be similarat some wavelengths butquite differentat others

Reflected spectral signatures of two important

alteration minerals, kaolinite in blue and alunite in

red. Wavelength is along the x-axis and is given in

microns from 2.0-2.5 um. Reflectance is reported in

percent from 0 1.0 on the y-axis. Minerals

lendthemselves easily to identification due to their

highly unique crystal geometries. Such signatures

can be measured in the field with a portable field

spectroradiometer such as the one sitting atop

kaolinite boulders in the photograph. They can also

be measured in the imagery itself.

Each materials on the earth (Land

Cover) have very unique spectral

signatures (different reflectance

pattern)

Spectral: in terms of wavelength

Optical RS is measuring spectral

energy or reflectance, from which

we can identify materials

Spectral Signatures Spectral Signatures CS5905 Spatial Informatics

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Categories of Remote Sensors

Remote sensors are based on

1. Specific regions of the EM spectrum

2. The types of EM energy being detected

3. The source of EM energy, e.g., passive

versus active sensors


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Types of EM energy detected by

remote sensors


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Coverage of Sensors


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Categories of Remote Sensors

Remote sensors are based on

1. Specific regions of the EM spectrum

2. The types of EM energy being detected

3. The source of EM energy, e.g., passiveversus active sensors


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Passive versus active systems

Passive systems record energy that isemitted, scattered or reflected from naturalsources (e.g., sunlight or based on thetemperature of the surface or atmospherebeing imaged)

Active systems provide their own source ofEM radiation, which is then reflected orscattered, and this signal detected by thesystem


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Passive and Active Sensors


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Through 7/31/2002

A map showing the number and location of Landsat 7scenes in the US archive.

Landsat 7 Global ArchiveCS5905 Spatial Informatics

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Remote Sensing Process


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Remote Sensing ProcessTransmission, Reception, and Processing (E): the energy

recorded by the sensor has to be transmitted, often inelectronic form, to a receiving and processing stationwhere the data are processed into an image (hardcopyand/or digital).

Interpretation and Analysis (F) the processed image isinterpreted, visually and/or digitally or electronically, toextract information about the target which was illuminated.

Image Interpretation Visual Interpretation

Digital Processing Preprocessing

Enhancement

Transformation

Classification

Integration


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US StationsInternational Cooperators

US & International Landsat Receiving

Stations

Data Receiving station


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Image Characteristics

Black & White photo Digital Image

Data Processing

Geometric Correction: to know the exact position and overlay withmaps.

R A

Preprocessing II


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Image Display

Primary colors displayed as

single channel with same

brightness level Red, Blue, and

Green

Primary colors displayed as

multiple channel with different

primary color at different

brightness


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Color Assignments


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Classification

Objectives of Classification

Carry out quantitative interpretation using mathematical /statistical modeling.

To assign corresponding class to groups with homogeneouscharacteristics, with the aim of discriminating multiple objectsfrom each other within the image.

The level is called class. Classification will be executed on thebase of spectrally defined features, such as density, texture etc.in the feature space. It can be said that classification divides thefeature space into several classes based on a decision rule.

Classes are for such as Land use, Land Cover, Crop Type,Forest Types, and etc.

To divide images into several number of classes. Landuse/Landcover

Further Analysis Further Analysis

Calculating Physical Parameters using Models


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Supervised and Un-Supervised

ClassificationSupervised Classification

Classify each pixel into a pre-established class. Population statistics of each class is to be identified by training areas.

Each pixel will be classified into a class which has similar (nearest )property with the pixel.

Un-supervised Classification

Analyze inherent structure of the data Unconstrained by external knowledge about area

When knowledge about the area is not enough

Combination

Un-Supervised Classification -> Ground Truth -> SupervisedClassification


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Advantage of RS Wide Coverage, Periodical Observation

Variety of Observing Method

Multi-resolution Multi-temporal Multi-spectral

Global Environment Local Application

Application Field Hydrology, Oceanography, Global Env. Study, CO2

Agriculture, Forestry, Fisheries, Ecological Mapping

Coastal zone management, Health Management, Energy Fire, Oil-spill, Volcano, Earthquake, Flood, Ice

Land use mapping, Cadastral Mapping, Topographic Map,Change Detection

Military

Use wisely by understanding advantage and limitation

Documents

Cl-1&2 RS Introduction