GEOM3003 Engineering Surveying (Mining) 1 The previous Slide Set contains: Spatial Information...

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GEOM3003 Engineering Surveying (Mining)

The previous Slide Set contains:• Spatial Information• Terrain Modelling• GIS, Geographic Information Systems

This Lecture Notes Slide Set contains:• Introduction to Remote Sensing

The next Silde Set contains:• Introduction to Photogrametry

Dr Gerd R Dowideit

School of Geography, Planning and ArchitectureThe University of Queensland

Copyright, 2004

2Start this PowerPoint Session as a Slide Show !

Engineering Surveying (Mining)THE UNIVERSITYOF QUEENSLAND


Remote SensingLecture 7, Part 1

Dr Gerd R Dowideit

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Remote Sensing

An Introduction:

What is REMOTE SENSING ?

REMOTE SENSING includes all methods and techniques used to gain qualitative and quantitative information about distant objects without coming into direct contact with these objects.Look-Look, NO Touch

Landsat TM Near IR Band

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Remote Sensing (RS) methods try to answer four basic questions:

HOW MUCH of WHAT is WHERE? What is the SHAPE and EXTENT of ... ? (Area, Boundaries, Lineaments, ...)Has it CHANGED?What is the MIX of Objects

Remote Sensing

An Introduction:


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HOW MUCH of WHAT is WHERE? WHAT: Type, Characteristic and Properties of Object. eg. Water, Vegetation, Land; Temperature, Concentration, State of Development; Subtype, Species, Use of ... ; Includes determination of generic object type, character and property as well as it’s abstract meaning.

=> DATA INTERPRETATION

Remote Sensing

An Introduction:


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HOW MUCH of WHAT is WHERE?HOW MUCH: determine by simple COUNTING, measuring AREA covered or percentage of total area coverage.WHERE: Relate locations and area covered to either a standard map or to the actual location on the ‘ground’ where the object occurs.NOTE: WHERE also refers to a moment in

time

Remote Sensing

An Introduction:


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What is the SHAPE and EXTENT of ... ? (Area, Boundaries, Lineaments)This extends the ‘WHERE’ to be a completely GEOMETRIC problem. MAP PRODUCTION methods are to be applied to the analysis of RS information. These include:

Photogrammetric Methods:Identification and Delineation of Boundaries and Lineaments (Roads, Rivers, Fault Lines)

Remote Sensing

An Introduction:


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Has it CHANGED?

CHANGE may occur with progress of TIME.Change may be detected through comparison of observed states at different moments in time.

=> CHANGE DETECTION

Remote Sensing

An Introduction:


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What is the MIX of Objects?The surface of the Earth is covered by objects like Soil, Water, Grass, Trees, Houses, Roads and so on. These are ‘GENERIC OBJECTS’. We know these well, but we also know objects like Open Forest, Residential and Industrial Estates, etc. Each of these ABSTRACT OBJECTS are made up of a typical collection of Generic Objects.

Remote Sensing

An Introduction:


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Remote Sensing (Look-Look, No Touch) is a much wider field than we will discuss in this lecture series. We will concentrate on that part of RS dealing with EARTH RESOURCES

Vision Medical Imaging

Sound and Radio Wave Detection

Remote Sensing

An Introduction:


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What makes it tick ???(1) RS requires a CARRIER of information, which can bridge distances.(2) RS requires a SENSOR which can detect changes in the carried Signal.(3) RS requires RECORDING, ANALYSIS, INTERPRETATION and REPRESENTATION of the sensed information in a purposeful way.

(1) RS requires a CARRIER of information, which can bridge distances.These Carriers of Information are FIELDS of FORCES:* Pressure Wave Fields of Sound,* Gravity Force Fields,* Magnetic Force Fields and* Electro-magnetic Force Fields.The latter are of our main interest, since they include visible and invisible LIGHT.

Remote Sensing

An Introduction:


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(2) RS requires a SENSOR which can detect changes in the carried Signal.Apart from our own eyes and ears, technology has provided us with a multitude of sensors operating in the detection of force fields:microphones, geophones,photographic film, video cameras and photo detectors,radio wave receivers, gravimeters and magnetometers.


Remote Sensing

An Introduction:


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(3) RS requires RECORDING, ANALYSIS, INTERPRETATION and REPRESENTATION of the sensed information in a purposeful way.This is a technique based topic. It is essential for the success or failure of RS in respect of it’s anticipated purpose.This topic will be dealt with in it’s main aspects (but not completely).


Remote Sensing

An Introduction:


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Source of ForceField

Reflection

Sensor System eg. Camera

Resulting RS Data Set

eg. Image

DATAACQUISITION

Remote Sensing

An Introduction: What is Remote Sensing

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RS Data Seteg. Image

DATAPROCESSING

Interpretation (secondary) Measurements

Data Processing & Mapping (geometric)Presentation of Processing Results

Explaining deduced OBJECT INFORMATION

Remote Sensing

An Introduction: What is Remote Sensing

Model of Real World

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Remote SensingElectromagnetic Radiation:

Fraunhofer Lines

(found empirically by observation)

Dispersion of Lightthrough a refractiveprism

Fraunhofer discovered ‘black lines’ in the spectrum of light emitted by various superheated chemical elements. These lines were as typical for each of the elements as fingerprints for humans.

Chemical Composition of objects effects emitted ER in a unique way for each element.

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Fraunhofer Lines

Dispersion of Lightthrough a refractiveprism

E = mc2

In Einstein's formula E = mc^2 E = Energy m = mass (of matter/object) c = propagation velocity of

lightWhat does that tell us ?There is a well defined relationship between MATTER, ENERGY and ELECTROMAGNETIC RADIATION (eg. light)

Remote Sensing

Electromagnetic Radiation:

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The basic building blocks of all matter are ATOMSThe basic building blocks of Atoms are the NUCLEUS (Neutrons and Protons) and several ELECTRONS.Electrons are thought to be spinning around the Nucleus at orbits of different, but well pre-defined discrete sequential radii.

A change in the energy level contained in an atom (eg. by heating or cooling) changesthe balance of forces inside the atom will automatically adept to energy level changes by moving electrons to higher or lower orbits.

Remote Sensing


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The loss of energy from an atom causes electrons to drop back to lower orbits which is of interest to us.One widely accepted theory says, that atoms lose energy in form of Electromagnetic Radiation

One theory explains ER as a WAVE field,another as a field of a stream of PHOTONS, particles so small that they have no mass. Both are said to propagate at light speed.

Photon

Wave

Energy differential = 1 Planck’s Quantum E = mc^2

Remote Sensing


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Photon

Wave


Some atoms may have been charged to a higher energy level; pushing electrons further than one orbital level. In turn they can drop back over more than one orbit level: more energy than one Quantum

Gerd’s interpretation:Since c is constant, all photons travel about 300,000 km/secThose with a higher energy charge will use a ‘more wiggly’ (thus, longer) wave path than those with lesser charge.

Remote Sensing


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Photon

Wave


Wave characteristics: = Wave length = distance between consecutive wave peaks (measured in m)f = frequency = number of wave peaks (wiggles) in the wave train propagating for 1 sec (measured in Hz) = c / fSumming up:High Energy Radiation proceeds at higher frequencies (shorter wavelength compares to low energy radiation.Radiation wave length mix depends on amount of (heat) energy contain in matter.

=>PLANCK’s LAWc = const ~ 300000 km/sec

Remote Sensing


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PLANCK’s LAW

Wave Length

Total RadiationEnergy emitted

Radiation Energy Curve foran object (BLACK BODY)at constant temperature.

short long

peak

WIEN’s LAW

Wave Length


Radiation Energy Curves foran object (BLACK BODY) at various constant temperatures.

short long

300K1000K

3000k6000K

Radiation output curves for ideal (Black Body) objects

Remote Sensing


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The Average Temperature of Earth’s Surface rarely exceeds 300 K, an object temperature to low to provide for EMITTED RADIATION of sufficient strength to register on most of the available sensors (except in thermal IR sensors).

(Even warm nights can be pitch black)

WIEN’s LAW

Wave Length


Radiation Energy Curves foran object (BLACK BODY) at various constant temperatures.

short long

300K1000K

3000k6000K

The surface of the Sun’s outer atmosphere (photosphere) has a temperature of about 5800K, hot enough to provide adequate radiation energy. (Peak output in GREEN of visible light).

Most RS systems utilise reflected sun light.

Remote Sensing


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QUESTION: Does incident sun light interact in a similar way with matter as described is the case for emitted radiation?

ANSWER: YES!

ER (including light) is a form of energy (as is heat). Matter (atoms) can absorb as well as emit energy.

Objects under illumination by sun light will partially absorb radiation.

Absorption level varies with wave length depending on chemical composition of the object

Radiation not absorbed is mostly reflected and available for RS.

=> Spectral Signatures

Remote Sensing


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GN238 Introduction to Remote Sensing 01/10/97 5

ER, the Physical Basis of RSExamples of Spectral Signatures

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0.4 (blue) 0.80.6 (red)0.5 (green) 0.7 (IR=>) 1.0 m

Reflectance

(of Sun Light)

0

Bare Soil (Grey/Brown)

Vegetation (green)

Water (clear)

(<= UV)

Remote Sensing


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ER, the Physical Basis of RSThe Electromagnetic Spectrum

(not to exact scale; see Textbook)

10^-6 10^-3 1 1000.1 10^5 10^8

-Rays

Sound

X-Ray UV

Visible

0.4 0.5 0.6 0.7 m

m

TV/RadioMicro-Wave

Thermal Infrared

Near & Mid Infrared

Wave Length

not part of ER)

Note: outsidethe visible Range,no colours orshades will be perceived.Blue Green Red

Remote Sensing


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The General Remote Sensing Model

I

R

AT

A

Sensor

RadiationSource

I = R + A + T

SimplifiedRadiation-Balance

R = I - A - T

I = Incident ERR = ReflectedA = AbsorbedT = TransmittedS = Scattering

S

Remote Sensing


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ER, the Physical Basis of RSA bright Idea for RS

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0.4 (blue) 0.80.6 (red)0.5 (green) 0.7 (IR=>) 1.0m

Reflectance

(of Sun Light)

0

Bare Soil (Grey/Brown)

Vegetation (green)

(<= UV)

G R IR

Veg. SoilG med medR low highIR high+ high

Truth Table

Remote Sensing


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A bright Idea for RS

G R IR

Truth Table

Veg. SoilG med medR low highIR high+ high

Remote Sensing


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ImageDisplay

Remote Sensing


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Ekati Diamond Mine,Northwest Territories

1989 1994 1999Colour codedCompsiteChange Detection:

Impact of Mine Development onthe Environment

Remote Sensing


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Spectral Classification of a Landsat MSS scene

Remote Sensing


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Using Fraunhofer’s ObservationsThe variation in Radiation output from a REAL OBJECT depends on it’s chemical composition. Water has a different SPECTRAL SIGNATURE than soil or chlorophyll containing leaf matter, etc.

Wave Length

Radiation Energy Curve foran object at constant temperature.

short long

Gerd’s realobject

QUESTIONS:• Can we use these facts to measure object temperatures?• Can we use these facts to identify the chemical composition of objects and• can we use the latter to identify the object itself?

Remote Sensing


GEOM3003 Engineering Surveying (Mining) 1 The previous Slide Set contains: Spatial Information...

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