Module-01 Fundamentals of Remote Sensing.pdf

7/27/2019 Module-01 Fundamentals of Remote Sensing.pdf

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Module-01: Fundamentals of Remote Sensing

Certificate Course on

Basic Training on Remote Sensing

Bangladesh Institute of Planners (BIP)Under the Professional Skill Development Program

By: Md. ESRAZ-Ul-Zannat

Date: 27 September 2013


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Md. ESRAZ-Ul-Zannat

MURP (BUET), BURP (BUET)

MBIP (509), RAJUK Enlisted (RP09004)

GIS & Remote Sensing Specialist

Information & Communication Technology (ICT) Division

Institute of Water Modelling (IWM)

House # 496, Road # 32, New DOHS, Mohakhali, Dhaka-1206

Cell: +8801712688268

Phone (Office): 8824590-91, 8802882205-6, Telex: 117

Fax: 88-02-8827901

Email (Personal): [email protected]

Email (Official): [email protected]

Web: www.iwmbd.org

Signature
mailto:[email protected]:[email protected]://www.iwmbd.org/http://www.iwmbd.org/mailto:[email protected]:[email protected]


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Outline

Fundamentals of Remote Sensing Electromagnetic energy (spectrum)

Interactions with the atmosphere

Characteristics of images

Resolution: spatial, spectral, temporal and radiometric

Basics of visual image interpretation

Remote Sensing technology.

Overview of different satellites and

Sensors


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Remote sensing is the science and art of

obtaining information about an object, area, orphenomenon through the analysis of data

acquired by a device that is not in contact with

the object, area, or phenomenon underinvestigation.

Definition


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Hearing, seeing, smelling are all remote

sensing, but we will focus on one kind:

Measurement, by satellite-borne sensors, of

the electromagnetic energy reflected or

emitted from objects on the Earths surface.

Remote Sensing

Source of image: http://rst.gsfc.nasa.gov/Intro/nicktutor_I-1.html

Collecting information without

being in contact with itMeasurement from a distance
http://rst.gsfc.nasa.gov/Intro/nicktutor_I-1.htmlhttp://rst.gsfc.nasa.gov/Intro/nicktutor_I-1.htmlhttp://rst.gsfc.nasa.gov/Intro/nicktutor_I-1.htmlhttp://rst.gsfc.nasa.gov/Intro/nicktutor_I-1.html


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Definition of Remote Sensing

Measurement from a distance.

Measurement, by satellite-borne sensors, of the electromagnetic energy

reflected or emitted from objects on the Earths surface.

Source of image: http://rst.gsfc.nasa.gov/Intro/nicktutor_I-1.html


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Satellites


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Types of Satellites


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Remote Sensing Satellites


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Whats standing between you and your signal???

The atmosphere

Terrain relief

Season

Sun angle

Partial spectral signatures


11/92Remote Sensing Realities | June

Remote sensing data must be corrected for

atmospheric, topographic, and solar effects if theyare to be compared to a library of spectral

reflectance curves. Furthermore, relative

atmospheric correction is needed if data

signatures from one image date are to becompared to those from another date.

Robert A. Schowengerdt, Remote Sensing: Models

and Methods for Image Processing



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A common radiometric response is required for

quantitative analysis of multiple satellite images ofa scene acquired on different dates with differentsensor.

Ideally, you want all image to appear as if theywere acquired with the same sensor while

observing through the same atmosphere andillumination conditions.

Hall et al., 1991



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Types of Satellites Orbits


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Types of Satellites Orbits

l


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Geostationary vs. polar orbiting sensors

Geostationary sensors orbitwith the earth continuallyviewing the samehemispheric area

Polar orbiters, continually

view new areas of the earthas the planet rotatesunderneaththe sensor. Keeps the samegeneral solar time as it cross

the equator on each orbit -called sun synchronous

Polar orbit


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GeostationaryField-of-View (FOV)

The field-of-view (FOV) of a Geostationary satellite (i.e., what itcan see from its vantage point in space) remains the same overtime, and is at most of the Earths surface (90 longitude oneeither side of the sub-orbital point on the equator).

sub-orbital point


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Nadir

Horizon

SolarZenithAngle

Zenith

ElevationAngle

OrbitalGeometry


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0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

250 500 750 1000 1250 1500 1750 2000 2250 2500

Wavelength (nm)

Radiance(Wm

-2n

m-1

sr-1

)

average shrub

average grass

average soil

0

0.1

0.2

0.3

0.4

0.5

0.6

250 500 750 1000 1250 1500 1750 2000 2250 2500

Wavelength (nm)

Reflectan

c

average shrub

average grass

average soil

1 2 3 4 5 7

What we

measurein remotesensing?


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Many more:

Temperature Soil moisture

Mineral and rock types

Rainfall

Snow cover, snow depth or snow water equivalent Vegetation type and biomass

Sea ice properties (concentration, thickness, extent,area)

Elevation and change Aerosol, gas types and concentration

You might name a few more?

What we measure in remote sensing?

Th d f Ed i i R i


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The need for Education in Remote Sensing

Pollution, population growth exceeding the

support capability of the land, loss of biodiversityand global climate change are only few of theproblems that face todays and tomorrowsgenerations. Remote sensing and related

technologies can contribute to ourunderstanding of these problems as well as theimplementation of practical solutions

Ad f i


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Advantages of remote sensing

Provides a regional view (large areas)

Provides repetitive looks at the same area Remote sensors "see" over a broader portion

of the spectrum than the human eye

Sensors can focus in on a very specificbandwidth in an image or a number ofbandwidths simultaneously

Provides geo-referenced, digital, data

Some remote sensors operate in all seasons,at night, and in bad weather

ll


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Satellite ImagesAdvantages

Covers large areas

Cost effective

Time efficient

Multi-temporal Multi-sensor

Multi-spectral

Overcomesinaccessibility

Faster extraction of GIS-ready data

Disadvantages

Needs groundverification

Doesnt offer details

Not the best tool forsmall areas

Needs expert system toextract data

R t S i A li ti


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Remote Sensing Applications

Land-use mapping

Forest and agriculture applications Telecommunication planning

Environmental applications

Hydrology and coastal mapping

Urban planning Emergencies and Hazards

Global change and Meteorology

Many more.

l f R


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Application of Remote sensing

Urbanization & Transportation Updating road maps

Asphalt conditions

Wetland delineation

Agriculture

Crop health analysis

Precision agriculture

Compliance mapping

Yield estimation

li i f R i


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Natural Resource Management Habitat analysis

Environmental assessment Pest/disease outbreaks

Impervious surface mapping

Lake monitoring

Hydrology

Landuse-Landcover monitoring

Mineral province Geomorphology

Geology

National Security

-Targeting

- Disaster mapping and monitoring

-Damage assessment

-Weapons monitoring

-Homeland security

-Navigation

-Policy

Application of Remote sensing

A li ti f N ti l P i it


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Agricultural

EfficiencyAir Quality

Water

ManagementDisaster

Management

Carbon

ManagementAviation

Ecological

ForecastingInvasive Species

Coastal

ManagementHomeland

Security

Energy

ManagementPublic Health

Applications of National Priority

l d


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Remotely Sensed Data

Aerial Camera Multispectral Satellite Radar Satellite Hyperspectral Sensor

Landsat/Ikonos/Quickbard Hyperion

P
http://landsat.gsfc.nasa.gov/earthasart/images/carnegie_hires.jpg


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Image Processing

Image Pre-Processing

- Image Restoration- Sensor Calibrations

- Atmospheric Corrections

- Solar Illumination Corrections

- Topographic Corrections

- Geometric Corrections

Image processing

- Spatial enhancement

- Spectral enhancement

- Classification

- Feature Extraction

I P i S ft


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Image Processing Software

ERDAS Imagine

ENVI

ILWIS

ArcGIS PCI Geomatica

Nature of Remote Sensing Data


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Nature of Remote Sensing Data

Quantized grid of small

areas on the Earths

surface. The energy of

reflected

electromagneticradiation in each grid

cell is a function of the

characteristics of the

objects in that cell.Landsat

Red = 5 (MIR)

Green = 4 (NIR)

Blue = 3 (Red)

B d


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A set of adjacent wavelengths or frequencies

with a common characteristic. For example,

visible light is one band of the electromagneticspectrum, which also includes radio, gamma,

radar and infrared waves.

Band

El t ti S t


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Electromagnetic waves are radiated through space from somesource. When the energy encounters an object, even a very

tiny one like a molecule of air, one of three reactions occurs.The radiation will be:

(1) reflected off the object,(2) absorbed by the object, or

(3) transmitted through the object.

Electromagnetic Spectrum

Some Light Is Reflected


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Some Light Is Reflected

Albedo:

reflective quality of a surface, expressed as percent of incident light reflected.

S


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Sensors Sensors - gather and process information

detect and measure photons.

Most air/space sensors are spectroradiometers

The term spectroradiometer is reserved for sensors

that collect the dispersed radiation in bands rather

than discrete wavelengths.

Spectroradiometry is the measurement of absolute

radiometric quantities in narrow bands of wavelength

All s s s sid l tf


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All sensors reside on a platform

Ground based sensors are

used to compare with infocollected by satellite

sensors.

S T h l


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Sensor Technology

EMR is reflectedor emittedfrom

target, through atmosphere,

monitored by sensor.

Sensors measure photons.

Critical component - the detector.

Ph l i ff (Alb Ei i )


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Photoelectric effect (Albert Einstein)

The release of electrons that occurs when

electromagnetic radiation comes in contact with a

metal.

Plate

EMR

Photoelectric effect

electrons

Signal


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Radiometeris a general term for any

instrument that quantitativelymeasures EMR.

Most sensors are spectroradiometers.

radiation collected in narrow spectral

bands.

Prism or diffraction grating - breaks

radiation into discrete wavelengths.

S S t


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Sensor System Platforms - Ground based ,Airborne , Satellite

Sensor Types

Passive, active

Imaging, nonimaging

Passive Sensors

Photographic

spectroradiometers

Passive microwave systems

Visible, infrared, and thermal imaging systems

Active Sensors - Radar, Lidar

T l ss s f s s s


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Two classes of sensors

Passive - radiation received comes from

external source, Sun.

Active - energy generated from within

sensor system, beamed outward, and

fraction returned is measured.

P ssi S ns s


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Passive Sensors

Sun provides source of energy

reflected (vis, near IR)

absorbed and re-emitted (thermal IR)

Passive sensors can only be used to detect ener

when the sun is illuminating the Earth.

thermal infrared - detected day or night.

A ti


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Active sensors

sensor emits radiation which is directed toward target.

radiation reflected from target is detected and measured

by sensor.

Active sensors


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Active sensors

Advantage

measurements anytime, regardless of time of

day or season.

can be used for examining wavelengths not

sufficiently provided by the sun, such as

microwaves.

Sensors can be


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non-imaging - measures radiation and

reports result as electrical signal

imaging - electrons released 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.

Sensors can be

Electromagnetic Spectrum


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ElectromagneticSpectrum

Source: http://oea.larc.nasa.gov/PAIS/DIAL.html

Remote Sensing Platforms


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Remote Sensing Platforms

Ground-based Airplane-based Satellite-based


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NASAResearch

Spacecraft


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In remote sensing, we are largely concerned with

REFLECTED RADIATION. This is the radiation that

causes our eyes to see colors, causes infrared film torecord vegetation, and allows radar images of the earth

to be created.

The source of a vast majority of this reflected radiation is

the sun.

Radiant Intensity


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Jensen, 2000

Radiant Intensity

of the Sun

What Does The Detector See?


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What Does The Detector See ?The instantaneous field of view (IFOV) is the cone

angle in which the incident energy on the detectoris focused.

Objective

Detector

Cone of light

Angle = IFOV

Useful conversion: the ground area

a detector sees ifnadir (pointed

straight down) is:

D = H*IFOV, whereD = diameter of circular ground

area viewed by the detector

H = height of the detector above

terrain

IFOV = angle (in radians) of the

systems instantaneous field of

viewD

H

Swath


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Swath

Area imaged on the ground

Imaging swaths for different sensors vary

from tens and hundreds of km wide.

Swath


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Earth is rotating (from west to east).

satellite swath covers new area with each

consecutive pass.

Allows complete coverage of Earth's

surface.

Swath

Describing Sensors


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Describing Sensors

Resolution: the smallest difference/unitsthat is resolvable by a sensor

Extent: the range of units of measurement

that a sensor can resolveFour Types:

1. Spatial

2. Spectral

3. Radiomatric

4. Temporal

Radiometric Resolution


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Spectral Resolution

1-bit8-bits

Landsat

IKONOS

Spatial Resolution


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The detail discernible in an image is

dependent on the spatial resolution of the

sensor.

SpatialResolution

Spatial Resolution


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Pixel size of satellite images

High spatial resolution: 0.5 - 4 m

Medium spatial resolution: 4 - 30 m

Low spatial resolution: 30 - > 1000 m

Landsat spatial resolution = 30m

SpatialResolution

Spatial Resolution


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SpatialResolution

Spatial Resolution


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SpatialResolution

General rule of thumb: the

spatial resolution should be less

than half of the size of the

smallest object of interest.

Spatial Extent


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Spatial Extent

Swath Width

Angular Field of View (AFOV)

Spectral Resolution


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Spectral Resolution

Spectral resolution

The number, wavelength position and width of spectralbands a sensor has

A band is a region of the EMR to which a set of

detectors are sensitive.

Multispectral sensors have a few, wide bands

Hyperspectral sensors have a lot of narrow bands

Spectral Resolution


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Number and position of bands in the

electromagnetic spectrum that the sensor

measures.

High spectral resolution: - 220 bands

Medium spectral resolution: 3 - 15 bands

Low spectral resolution: - 3 bands

Landsat = 7 bands

Spectral Resolution


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Spectral

Resolution

Jensen, 2000

Radiometric Resolution and Extent


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Radiometric Resolution and Extent Radiometric resolution: the difference in signal

strength resolvable by the sensor

Reported in terms of bits: n-bits = 2n levels ofsensitivity.

A 6-bit sensor can record 26 levels ofbrightness, or 64 levels. A 12-bit sensor canrecord 212 levels of brightness, or 4096 levels.

Radiometric extent: the range of brightness values asensor band is sensitive to: While there is a zero point (e.g. zero radiance is

received by the sensor), there is no physical limit onhow bright a pixel can be. Depending on the purposeof the sensor, this maximum is set accordingly. Itcan be controlled by having a smaller IFOV, shortersampling time or narrower bands.



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The actual information content in an image.

The sensitivity of the sensor to the magnitude of

electromagnetic energy determines the

radiometric resolution

refers to the smallest change in intensity level that

can be detected by the sensing system.




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In a digital image, the radiometric resolution is

limited by the number of discrete levels used to

digitize the continuous intensity value.

Digital Number (DN) - each pixel has a discrete

value made by converting the analog signalto

digital values of whole numbers over a finite range.

Landsat system range is 28, 0 to 255




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8-bit

256 greys

6-bit

64 greys

4-bit

16 greys

3-bit

8 greys

2-bit

4 greys

1-bit

2 greys


Bit Depth


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Bit DepthThe range of values that a particular raster format can store,

based on the formula 2n. An 8-bit depth dataset can store 256

unique values. Range of values by pixel depth.

Bit depth Range of values that each cell can contain

1 bit 0 to 12 bit 0 to 3

4 bit 0 to 15

Unsigned 8 bit 0 to 255

Signed 8 bit -128 to 127

Unsigned 16 bit 0 to 65535

Signed 16 bit -32768 to 32767

Unsigned 32 bit 0 to 4294967295Signed 32 bit -2147483648 to 2147483647

Floating-point 32 bit -3.402823466e+38 to 3.402823466e+38

Bit Depth

Radiometric Extent


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Maximum

brightness = 255

Maximum

brightness = 127

Rad ometr c Extent

Temporal Resolution and Extent


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Temporal resolution: the shortest amount of timebetween image acquisitions of a given location.

Temporal extent: the time between sensor launch

and retirement.

Important to consider if historical data is necessary.



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Specifies the revisiting frequency of a satellite

sensor for a specific location.

High temporal resolution: < 24 hours - 3 days

Medium temporal resolution: 4 - 16 days

Low temporal resolution: > 16 days

Landsat = 16 days


Temporal Resolution


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Temporal Resolution

MISR and MODIS are both on the TERRA satellite:

MISR has a swath width of 360 km. andimages the earth once every 9 days.

MODIS has a swath width of 2,330 km.and images the earth once every 1 to 2

days.

Temporal Extent


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p

The temporal extent of satellites is their launch to

retirement date.

There are continuity missions for certain sensors,

where an older sensor is replaced by a newer onebefore retirement.

LANDSAT sensors (1-7, except 6 which never made it

to orbit) have been operating continuously since 1972.

GOES (8-10) have been operating since 1994.


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PixelSize

Spectral Band Width


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Pixel

Size

Swath Width


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SwathWidth

Repeat Time


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Fundamental Principle of Studies Using Remote Sensing: For any given

material, the amount of radiation that is reflected (absorbed, transmitted)

varies with wavelength. Different materials have different reflectance

characteristics.


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For any given material, the amount of radiation that is reflected

(absorbed, transmitted) varies with wavelength.


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The satellite images, consist of numbers which

are measurements of the amount of energy thathas been reflected from the earth's surface in

different wavelength bands. Some of these bands,

such as the infrared bands which contain so

much information about vegetation growth andcondition, can't be seen with the human eye The

numbers recorded for the different satellite

bands are displayed in red, green and blue colourguns on a computer screen.

Reflectance spectra ofvegetation


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vegetation

--Chlorophyll reflects higherGreen andInfrared, but absorbs more Red

--NDVI is (IR-R)/(IR+R); range is1 to +1

-- NDVI of an actively photosynthesizing leaf

is, e.g. (72-22)/(72+22) = 0.53

Colored lines

approx. represent

TM bands 1-4

Modified from Jensen, J. 2000. Remote Sensing of the Environment. Prentice-Hall


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Land cover

Land use (inside Protected Area(PA) and adjacent lands)

Fragmentation

Vegetation health

Vegetation parameters (NDVI, NPP,LAI)

Frequency of invasive species

Climate change impacts

Air quality Water quality

Streamflow

Inputs (nitrogen, mercury)

Remote Sensing?

Sensor networks?

}Sensor networks?


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Landsat Satellite


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Landsat 1 (originally named Earth Resources Technology Satellite

1): launched July 23, 1972, terminated operations January 6, 1978

Landsat 2: launched January 22, 1975, terminated January 22, 1981Landsat 3: launched March 5, 1978, terminated March 31, 1983

Landsat 4: launched July 16, 1982, terminated 1993

Landsat 5: launched March 1, 1984, still functioning, but severe

problems since November 2011. On December 26, 2012, USGS

announced that Landsat 5 will be decommissioned.

Landsat 6: launched October 5, 1993, failed to reach orbit

Landsat 7: launched April 15, 1999, still functioning, but with faulty

scan line corrector (May 2003)

Landsat 8: Landsat Data Continuity Mission was launched February11, 2013. May 30, 2013 Landsat Data Continuity Mission was

turned over to USGS and renamed Landsat 8

Landsat Thematic Mapper (TM)
http://en.wikipedia.org/wiki/Landsat_1http://en.wikipedia.org/wiki/Landsat_2http://en.wikipedia.org/wiki/Landsat_3http://en.wikipedia.org/wiki/Landsat_4http://en.wikipedia.org/wiki/Landsat_5http://en.wikipedia.org/wiki/Landsat_6http://en.wikipedia.org/wiki/Landsat_7http://en.wikipedia.org/wiki/Landsat_8http://en.wikipedia.org/wiki/Landsat_8http://en.wikipedia.org/wiki/Landsat_8http://en.wikipedia.org/wiki/Landsat_8http://en.wikipedia.org/wiki/Landsat_7http://en.wikipedia.org/wiki/Landsat_7http://en.wikipedia.org/wiki/Landsat_7http://en.wikipedia.org/wiki/Landsat_6http://en.wikipedia.org/wiki/Landsat_6http://en.wikipedia.org/wiki/Landsat_6http://en.wikipedia.org/wiki/Landsat_5http://en.wikipedia.org/wiki/Landsat_5http://en.wikipedia.org/wiki/Landsat_5http://en.wikipedia.org/wiki/Landsat_4http://en.wikipedia.org/wiki/Landsat_4http://en.wikipedia.org/wiki/Landsat_4http://en.wikipedia.org/wiki/Landsat_3http://en.wikipedia.org/wiki/Landsat_3http://en.wikipedia.org/wiki/Landsat_3http://en.wikipedia.org/wiki/Landsat_2http://en.wikipedia.org/wiki/Landsat_2http://en.wikipedia.org/wiki/Landsat_2http://en.wikipedia.org/wiki/Landsat_1http://en.wikipedia.org/wiki/Landsat_1http://en.wikipedia.org/wiki/Landsat_1


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pp

7 channel sensor mounted on the Landsat platform

sun-synchronous, near-polar orbit

altitude 705 km.

16 day repeat coverage

30 m ground resolution across a swath of 185

km

except for thermal data -120 m ground

resolution.



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Bands

BLUE (0.45-0.52 m): water body penetration,

coastal water mapping, soil/vegetation

discrimination, forest type mapping, culturalfeature identification.

GREEN (0.52-0.60 m): green reflectance peak

of veg. for discrimination and vigor assessment,

cultural feature identification.

pp



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RED (0.63-0.69 m): chlorophyll absorption

region aiding in plant species differentiation,

cultural feature identification.

NEAR INFRARED (0.76-0.90 m): determining

vegetation types, vigor, and biomass content,

delineating water bodies, soil moisture

discrimination.



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MID-INFRARED (1.55-1.75 m): vegetation moisture

content and soil moisture, differentiation of snow from

clouds.

FAR-INFRARED (2.08-2.35 m): discrimination of

mineral and rock types, vegetation moisture content.

THERMAL INFRARED (10.4-12.5 m): vegetation

stress analysis, soil moisture discrimination, and thermal

mapping applications.

Sensor Summarization


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Image Processing Services


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g g

Our standard image processing

includes: Orthorectification

Client provided control (GCPs)

RPC (Sensor) Model

Mosaicking and tonal balancing

Cloud patching / haze correction

Colour enhancements

Image compression (ECW/SID)

Elevation Data Generation


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DTM generation from stereo imagery:

DEM (regular grid at 1-5m)

Contours (1m)

Breaklines (including hydrography and

access features) Random mass-points at high and low points

Vertical accuracy of +/- 1 to 1.5m with

surveyed control


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ThankingYou


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Documents

Module-01 Fundamentals of Remote Sensing.pdf