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Geographic Information Systems

GIS Data - Remote Sensing

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Remote Sensing Definition

"I want to know how God created this world. I am not interested in

this or that phenomenon, in the spectrum of this or that element. I

want to know His thoughts; -the rest are details. Albert Einstein

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Remote Sensing Definition ..

The technique of collecting information from adistance without physical touch

Remotely sensed dataAerial photography

Digital satellite images

Radar imagesetc.

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2. Properties of EM Energy

EM travels at the speed of light 3x108m/sec

Wavelength land Frequency n

l

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Properties ..

The type of energy is defined by its position inthe EM spectrum in terms of wavelength,measured bymm

1m = 1,000mm, 1mm = 1,000mm

http://kr.blog.yahoo.com/bmw26z/2188

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Properties ..

http://www.crisp.nus.edu.sg/~research/tutorial/atmoseff.htm#windows

Atmospheric windowsThose wavelengths that are relatively easilytransmitted through the atmosphere

The windows: UV, visible, near infrared, midinfrared, far infrared, microwave

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Properties ..

Atmospheric scattering

The redirection of EM energy by particlessuspended in the atmosphere or large molecules

of atmospheric gases Radiation of short wavelength is easier to be

scattered

http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/opt/mch/sct.rxml

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Properties ..

Responses of features on earth to EM energy

Reflection (%), transmission (%), and absorption(%)

Reflection + Transmission + Absorption = 100%

Reflection Absorption Transmission

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Properties ..

Reflection

- Light ray is redirected as it strikes anontransparent surface

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Properties ..

Reflection

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Properties ..

Transmission

Radiation passes through a substance withoutsignificant attenuation

Transmittance (t):transmitted radiation

t = ---------------------------

incident radiation

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Properties

http://www.crisp.nus.edu.sg/~research/tutorial/infrared.htm

Absorption and emission

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3 (1) Aerial Photography

Photographic cameras

Uses aerial cameras and film

Mounted on an aircraft

Produces aerial photographs

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3 (2) Electro-Optical Remote Sensing

Electro-Optical scanners

Uses light-sensitive detectors

Mounted on spacecrafts or aircrafts

Generates digital images

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http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=4396

Buffalo, NYNovember 20,

2000

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http://www.esri.com/news/pressroom/hurricanemaps.html

Biloxi Coast

Before HurricaneKatrina, April 12, 2005 Biloxi Coast

After HurricaneKatrina, August 31, 2005.

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3 (3) Microwave Remote Sensing

Uses antennas as detectors Passive microwave systems

Active microwave systems,

RADAR

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http://www.erh.noaa.gov/buf/

http://rst.gsfc.nasa.gov/Sect8/Sect8_3.html

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Operation ..

Pixel and IFOV

Pixel - picture element

IFOV - Instantaneous

Field of View - Theground area viewed bythe sensor at a giveninstant

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Operation ..

Sensors and detectors

Each sensor system contains a set of detectors,each set is sensitive to a certain range of

wavelength (band)Detectors of each band produce a digital image,

which is a matrix consisting of rows and columnsof pixels

The digital number of each pixel measures theintensity of energy received from the IFOV areaon the ground

Images of several bands result in a composite

image

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Operation

True and false color composite images

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5. Types of Resolution

Spectral resolution

Radiometric resolution

Spatial resolution

Temporal resolution

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5(2) Spatial Resolution

A measure of the smallest angular or linearseparation between two objects that can berevolved by the sensor, 30m, 1m, 1km

10m 20m 40m 80m

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5(3) Radiometric Resolution

The sensitivity of a detector to differences insignal strength as it records the radiant levels

2 levels 4 levels 16 levels 256 levels

1 bit 2 bit 4 bit 8 bit

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5(4) Temporal Resolution

How often a given sensor obtains imagery of aparticular area, e.g., 16 days, daily

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6. Commonly Used Satellite ImageData

Moderate resolution land satellites

Landsat

SPOT

Landsat 5, New York

http://landsat.gsfc.nasa.gov/images/gallery.html

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6. Commonly Used Satellite Image Data

High resolution land satellites

IKONOS

Orbview

GeoEye

QuickBird

IKONOS images: Washington DC, Hoover Dam, Hollywood
http://www.geoeye.com/gallery/default.htmhttp://www.geoeye.com/gallery/default.htm

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6. Commonly Used Satellite ImageData ..

Meteorologicalsatellites

AVHRR

EOS

Sea surface temperature in hurricanealley. This false color composite image ismade using data taken by AMSR-E on

board EOS, May 2002.AVHRR

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Radar systems

RADARSET

LIDAR

RADARSET

Courtesy of EarthData TechnologiesLIDAR

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Digital aerialphotographs

DOQQ

LIDAR

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Readings

Chapter 8

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