remote sensing [compatibility mode]

Introduction to Introduction to Remote SensingRemote Sensing

Prof. Prof. SumantaSumanta DasDasDept. of civil Dept. of civil EnggEngg..

MEFGI, RajkotMEFGI, Rajkot

Image: NASA 2005

ND GIS Users Workshop ND GIS Users Workshop Bismarck, ND October 24Bismarck, ND October 24--26, 26,

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OutlineOutline

Remote Sensing DefinedRemote Sensing Defined ResolutionResolution Electromagnetic Energy (EMR)Electromagnetic Energy (EMR) TypesTypes InterpretationInterpretation ApplicationsApplications


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Remote Sensing DefinedRemote Sensing Defined

Remote Sensing is:Remote Sensing is:

“The art and science of obtaining information “The art and science of obtaining information about an object without being in direct contact about an object without being in direct contact with the object” (Jensen 2000).with the object” (Jensen 2000).

There is a medium of transmission involved.There is a medium of transmission involved.


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EnvironmentalEnvironmental Remote Sensing:Remote Sensing:

… the collection of information about Earth surfaces … the collection of information about Earth surfaces and phenomena using sensors not in physical contact and phenomena using sensors not in physical contact with the surfaces and phenomena of interest. with the surfaces and phenomena of interest.

We will focus on data collected from an overhead We will focus on data collected from an overhead perspective via transmission of electromagnetic perspective via transmission of electromagnetic radiation.radiation.


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Source: Jensen (2000)


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Remote Sensing Includes:Remote Sensing Includes:

A) The mission plan and choice of sensors;A) The mission plan and choice of sensors;

B) The reception, recording, and processing of the B) The reception, recording, and processing of the signal data; andsignal data; and

C) The analysis of the resultant data.C) The analysis of the resultant data.

Types of Remote Sensing:Types of Remote Sensing:--

Based on Range of Electromagnetic Based on Range of Electromagnetic Spectrum:Spectrum:--

1.1. Optical Remote Sensing.Optical Remote Sensing.2.2. Thermal Remote Sensing.Thermal Remote Sensing.3.3. Microwave Remote Sensing.Microwave Remote Sensing.

Based on the source of the energy:Based on the source of the energy:--1.1. Active remote sensing.Active remote sensing.2.2. Passive remote sensing.Passive remote sensing.

Optical Remote Sensing:Optical Remote Sensing:-- The optical remote sensing devices The optical remote sensing devices

operate in the visible, near infrared, operate in the visible, near infrared, middle infrared and short wave middle infrared and short wave infrared portion of the electromagnetic infrared portion of the electromagnetic spectrum. spectrum.

These devices are sensitive to the These devices are sensitive to the wavelengths ranging from 300 nm to wavelengths ranging from 300 nm to 3000 nm. 3000 nm.

Based on Range of Electro Based on Range of Electro magnetic Spectrum:magnetic Spectrum:--

Thermal Remote Sensing:Thermal Remote Sensing:--

The sensors, which operate inThe sensors, which operate inthermal range of electromagneticthermal range of electromagneticspectrum record, the energyspectrum record, the energyemitted from the earth features inemitted from the earth features inthe wavelength range of 3000 nm tothe wavelength range of 3000 nm to5000 nm and 8000 nm to 14000 nm. 5000 nm and 8000 nm to 14000 nm.

Microwave Remote Sensing:Microwave Remote Sensing:--

A microwave remote sensor records the A microwave remote sensor records the backscattered microwaves in the backscattered microwaves in the wavelength range of 1 mm to 1 m of wavelength range of 1 mm to 1 m of electromagnetic spectrum. electromagnetic spectrum.

Most of the microwave sensors are active Most of the microwave sensors are active sensors, having there own sources of sensors, having there own sources of energy. energy.

Depending on the source of the Depending on the source of the energy:energy:--

Active remote sensing:Active remote sensing:-- Active remote sensing Active remote sensing uses an artificial source for uses an artificial source for

energy. energy. For example the satellite itself can send a pulse of For example the satellite itself can send a pulse of

energy which can interact with the target. energy which can interact with the target. In active remote sensing, humans can control the In active remote sensing, humans can control the

nature (wavelength, power, duration) of the source nature (wavelength, power, duration) of the source energy. energy.

Active remote sensing can be carried out during Active remote sensing can be carried out during day and night and in all weather conditions.day and night and in all weather conditions.

ExampleExample-- RADARRADAR

Passive remote sensing:Passive remote sensing:--

Passive remote sensing Passive remote sensing depends on a natural depends on a natural source to provide energy. source to provide energy.

The sun is the most powerful and commonly The sun is the most powerful and commonly used source of energy for passive remote used source of energy for passive remote sensing. sensing.

The satellite sensor in this case records primarily The satellite sensor in this case records primarily the radiation that is reflected from the target. the radiation that is reflected from the target.

Fig. active & passive remote sensing.Fig. active & passive remote sensing.


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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)Source: Canadian Centre for Remote Sensing

Remote Sensing Process Components

EM energy interaction of earth surface:

Advantages of remote sensing:Advantages of remote sensing:--

Provides a regional view (large areas). Provides a regional view (large areas). Provides repetitive looks at the same area. Provides repetitive looks at the same area. Remote sensors "see" over a broader. Remote sensors "see" over a broader.

portion of the spectrum than the human portion of the spectrum than the human eye. eye.

Provides geoProvides geo--referenced, digital, data. referenced, digital, data. Some remote sensors operate in all Some remote sensors operate in all

seasons, at night, and in bad weather.seasons, at night, and in bad weather. Give information of inaccessible area. Give information of inaccessible area.

DISADVANTAGE OF REMOTE DISADVANTAGE OF REMOTE SENSING:SENSING:--

• Expensive to build and operate.• Expensive to build and operate.

• Measurement uncertainty can be • Measurement uncertainty can be large.large.

• Data interpretation can be difficult.• Data interpretation can be difficult.

Applications of Remote Applications of Remote Sensing:Sensing:--

Agriculture:Agriculture:--

Crop type classification. Crop type classification. Crop condition assessment. Crop condition assessment. Crop yield estimation.Crop yield estimation. Mapping of soil characteristic.Mapping of soil characteristic. Soil moisture estimation.Soil moisture estimation.

Geology:Geology:--

Lithological mapping. Lithological mapping. Mineral exploration. Mineral exploration. Environmental geology. Environmental geology. Sedimentation mapping and Sedimentation mapping and monitoring. monitoring. GeoGeo--hazard mapping. hazard mapping. Glacier mapping.Glacier mapping. Hydrocarbon exploration and mine Hydrocarbon exploration and mine

explorationexploration

Urban Planning:Urban Planning:--

Land parcel mapping. Land parcel mapping. Infrastructure mapping. Infrastructure mapping. Land use change detection. Land use change detection. Future urban expansion planning.Future urban expansion planning.

Hydrology:Hydrology:-- Watershed mapping and management. Watershed mapping and management. Flood delineation and mapping. Flood delineation and mapping. Ground water targeting.Ground water targeting.

Land Use/Land Cover Land Use/Land Cover mapping:mapping:--

Natural resource management. Natural resource management. Wildlife protection.Wildlife protection. Encroachment.Encroachment. LULC change detection & analysisLULC change detection & analysis

Ocean applications:Ocean applications:--

Storm forecasting. Storm forecasting. Water quality monitoring. Water quality monitoring. Aquaculture inventory and monitoring. Aquaculture inventory and monitoring. Navigation routing. Navigation routing. Coastal vegetation mapping. Coastal vegetation mapping. Oil spill.Oil spill. Coastal hazard monitoring & Coastal hazard monitoring &

assessment.assessment.

Civil Engineering:Civil Engineering:--

Building construction(ICONOS,LIDAR)Building construction(ICONOS,LIDAR) City and Town planning & developmentCity and Town planning & development SurveyingSurveying Ground water exploration and mappingGround water exploration and mapping Site investigationSite investigation Land information system(LIS)Land information system(LIS)


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ResolutionResolution AllAll remote sensing systems have remote sensing systems have four typesfour types of of

resolution:resolution:

SpatialSpatial

SpectralSpectral

TemporalTemporal

RadiometricRadiometric


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High vs. Low?

Spatial Resolution



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SpectralResolution


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Temporal Resolution

Time

July 1 July 12 July 23 August 3

11 days

16 days

July 2 July 18 August 3


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Radiometric Resolution

6-bit range0 63

8-bit range0 255

010-bit range

1023


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Electromagnetic RadiationElectromagnetic Radiation


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Electromagnetic SpectrumElectromagnetic Spectrum


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Signature SpectraSignature Spectra


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RS DataRS Data-- AVHRR (Advanced Very AVHRR (Advanced Very High Resolution Radiometer) NASAHigh Resolution Radiometer) NASA


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GOES (Geostationary Operational GOES (Geostationary Operational Environmental Satellites) IR 4Environmental Satellites) IR 4


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MODIS (250 m)MODIS (250 m)


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Landsat TM Landsat TM (False Color Composite)(False Color Composite)


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SPOT (2.5 m)SPOT (2.5 m)


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QUICKBIRD (0.6 m)QUICKBIRD (0.6 m)


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IKONOS (4 m Multispectral) IKONOS (4 m Multispectral)


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IKONOS (1 m Panchromatic)IKONOS (1 m Panchromatic)


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RADAR RADAR (Radio Detection and Ranging)(Radio Detection and Ranging)

Image: NASA 2005

LIDAR LIDAR (Light Detection and Ranging)(Light Detection and Ranging)

Image: Bainbridge Island, WA courtesy Pudget Sound LIDAR Consortium, 2005


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Elements of Image InterpretationElements of Image Interpretation

Shape:Shape: Many natural and humanMany natural and human--made features have made features have

unique shapes.unique shapes.

Often used are adjectives like linear, Often used are adjectives like linear, curvilinear, circular, elliptical, radial, square, curvilinear, circular, elliptical, radial, square, rectangular, triangular, hexagonal, star, rectangular, triangular, hexagonal, star, elongated, and amorphous.elongated, and amorphous.


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Jensen (2000)

ShapeShape


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Elements of Image InterpretationElements of Image Interpretation Shadow:Shadow:

Shadow reduction is of concern in remote sensing Shadow reduction is of concern in remote sensing because shadows tend to obscure objects that because shadows tend to obscure objects that might otherwise be detected.might otherwise be detected.

However, the shadow cast by an object may be However, the shadow cast by an object may be the only real clue to its identity.the only real clue to its identity.

Shadows can also provide information on the Shadows can also provide information on the height of an object either qualitatively or height of an object either qualitatively or quantitatively.quantitatively.


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Jensen (2000)

ShadowShadow


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Elements of Image InterpretationElements of Image Interpretation Tone and Color:Tone and Color:

A A bandband of EMR recorded by a remote sensing of EMR recorded by a remote sensing instrument can be displayed on an image in instrument can be displayed on an image in shades of gray ranging from black to white.shades of gray ranging from black to white.

These shades are called “tones”, and can be These shades are called “tones”, and can be qualitatively referred to as dark, light, or qualitatively referred to as dark, light, or intermediate (humans can see 40intermediate (humans can see 40--50 tones).50 tones).

Tone is related to the amount of light reflected Tone is related to the amount of light reflected from the scene in a specific wavelength interval from the scene in a specific wavelength interval (band).(band).


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Jensen (2000)

Tone and ColorTone and Color


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Elements of Image InterpretationElements of Image Interpretation Texture:Texture:

Texture refers to the arrangement of tone or color Texture refers to the arrangement of tone or color in an image.in an image.

Useful because Earth features that exhibit similar Useful because Earth features that exhibit similar tones often exhibit different textures.tones often exhibit different textures.

Adjectives include smooth (uniform, Adjectives include smooth (uniform, homogeneous), intermediate, and rough (coarse, homogeneous), intermediate, and rough (coarse, heterogeneous).heterogeneous).


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TextureTexture


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Elements of Image InterpretationElements of Image Interpretation Pattern:Pattern:

Pattern is the spatial arrangement of objects on Pattern is the spatial arrangement of objects on the landscape.the landscape.

General descriptions include random and General descriptions include random and systematic; natural and humansystematic; natural and human--made.made.

More specific descriptions include circular, oval, More specific descriptions include circular, oval, curvilinear, linear, radiating, rectangular, etc.curvilinear, linear, radiating, rectangular, etc.


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Jensen (2000)

PatternPattern


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Elements of Image InterpretationElements of Image Interpretation Height and Depth:Height and Depth:

As discussed, shadows can often offer clues to the As discussed, shadows can often offer clues to the height of objects.height of objects.

In turn, relative heights can be used to interpret In turn, relative heights can be used to interpret objects.objects.

In a similar fashion, relative depths can often be In a similar fashion, relative depths can often be interpreted.interpreted.

Descriptions include tall, intermediate, and short; Descriptions include tall, intermediate, and short; deep, intermediate, and shallow.deep, intermediate, and shallow.


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Height and DepthHeight and Depth


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Elements of Image InterpretationElements of Image Interpretation Association:Association:

This is This is veryvery important when trying to important when trying to interpret an object or activity.interpret an object or activity.

AssociationAssociation refers to the fact that certain refers to the fact that certain features and activities are almost always features and activities are almost always related to the presence of certain other related to the presence of certain other features and activities.features and activities.


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Jensen (2000)

AssociationAssociation


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Digital Image processingDigital Image processing Correction of dataCorrection of data Digital enhancement for the purpose of better visual Digital enhancement for the purpose of better visual

interpretation.interpretation. It involves three basic steps:It involves three basic steps:1.1. Image preprocessingImage preprocessing2.2. Image processingImage processing3.3. Post processing & transformationPost processing & transformation

Why do we need image Why do we need image processing?processing?

oo Improvement of pictorial information for Improvement of pictorial information for human perceptionhuman perception

oo Image processing for autonomous Image processing for autonomous machine applicationmachine application

oo Efficient storage and transmissionEfficient storage and transmission


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Knowledge base

Image Acquisition

CompressionWavelet &

multiresolution processing

Image Filtering & Enhancement

Image Restoration

Color Image Processing

Segmentation

Morphological Processing

Representation & Description

Object Recognition

Image preprocessingImage preprocessing

Geometric correctionGeometric correction Radiometric correctionRadiometric correction


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Geometric correctionGeometric correction GeometricGeometric correctionscorrections areare mademade toto correctcorrect thethe

inaccuracyinaccuracy betweenbetween thethe locationlocation coordinatescoordinates ofof thethepicturepicture elementselements inin thethe imageimage data,data, andand thethe actualactuallocationlocation coordinatescoordinates onon thethe groundground.. SeveralSeveral typestypes ofofgeometricgeometric correctionscorrections includeinclude system,system, precision,precision, andandterrainterrain correctionscorrections..

Radiometric correctionRadiometric correction

RadiometricRadiometric correctionscorrections areare mademade toto thethe rawraw digitaldigitalimageimage datadata toto correctcorrect forfor brightnessbrightness values,values, ofof thethe objectobjectonon thethe ground,ground, thatthat havehave beenbeen distorteddistorted becausebecause ofofsensorsensor calibrationcalibration oror sensorsensor malfunctionmalfunction problemsproblems.. TheThedistortiondistortion ofof imagesimages isis causedcaused byby thethe scatteringscattering ofofreflectedreflected electromagneticelectromagnetic lightlight energyenergy duedue toto aaconstantlyconstantly changingchanging atmosphereatmosphere.. ThisThis isis oneone sourcesource ofofsensorsensor calibrationcalibration errorerror..


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Image processing Image processing

Enhancing an image or extracting Enhancing an image or extracting information or features from an imageinformation or features from an image

Computerized routines for information Computerized routines for information extraction (extraction (egeg, pattern recognition, , pattern recognition, classification) from remotely sensed classification) from remotely sensed images to obtain categories of information images to obtain categories of information about specific features.about specific features.


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Spatial filteringSpatial filtering Image quality and statistical evaluationImage quality and statistical evaluation Image contrast enhancement and sharpeningImage contrast enhancement and sharpening Image classificationImage classification

Pixel basedPixel based ObjectObject--oriented basedoriented based


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Post processing & transformationPost processing & transformation

Accuracy assessment of classificationAccuracy assessment of classification PostPost--classification and GISclassification and GIS Change detectionChange detection


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Clouds in ETM+Clouds in ETM+

Striping Noise and RemovalStriping Noise and Removal

CPCACPCA

Combined Principle Combined Principle Component AnalysisComponent Analysis

Xie et al. 2004

Speckle Noise and Speckle Noise and RemovalRemoval

GG--MAPMAP

Blurred objectsBlurred objectsand boundaryand boundary

Gamma Maximum A Posteriori Filter


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remote sensing [compatibility mode]

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