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Remote Sensing

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The science, art and technology associated with the acquisition and ... Includes photogrammetry. Photogrammetry. Def'n. Extraction of quantitative information ... – PowerPoint PPT presentation

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Title: Remote Sensing


1
Remote Sensing
  • Topic 1 Fundamentals of
  • Remote Sensing
  • Chapter 1 Lillesand and Keifer

2
  • Remote Sensing
  • Defn.
  • The science, art and technology associated with
    the acquisition and analysis of data about an
    object, area, or phenomenon without direct
    contact

3
A Simple RS System
4
Elements of a CompleteRemote Sensing System
5
Data Acquisition
a) Energy Source EMR from Sun, flashbulb, or
transmitted from antenna
6
Data Acquisition
b) Propagation reflection, refraction and
absorption of energy as it moves toward object of
interest
7
Data Acquisition
c) Incident Energy reflection, refraction and
absorption of energy as it strikes object of
interest
8
Data Acquisition
b) Propagation reflection, refraction and
absorption of energy as it moves away from object
of interest
9
Data Acquisition
d) Sensor and Platform detection, quantification
and recording energy in various wavelengths
10
Data Acquisition
f) Data Products - distribution of data in hard
copy or digital format
11
Data Analysis
g) Interpretation and Analysis - extraction of
information through visual interpretation,
photogrammetric techniques and digital image
analysis
12
Data Analysis
Reference Data maps, photographs, reports, and
other ancillary data used to facilitate analysis
13
Data Analysis
h) Information Products computer display, maps,
reports, geospatial databases, etc.
14
Data Analysis
i) Users managers, politicians, policy makers
that use information to make decisions
15
Airphoto Interpretation
  • Defn
  • The analysis of all types of aerial photography
    to extract quantitative and qualitative
    information
  • Uses a variety of cameras, films and filters
  • Includes photogrammetry

16
Photogrammetry
  • Defn
  • Extraction of quantitative information
  • Typically uses vertical photos
  • Includes measures of
  • Distance
  • Area
  • Direction
  • and Height

17
EMR
  • EMR is energy
  • Sun is most common source
  • Detected by passive RS systems

18
EMR
  • Modern physics acknowledges dual nature of EMR
  • The wave-particle duality refers to how EMR of
    differing wavelengths behaves, not what it is
  • Low frequency EMR tends to act more like a wave
    higher frequency EMR tends to act more like a
    particle

19
Wave Model
  • EMR travels as a set of sinusoidal orthogonal
    harmonic waves travelling at the speed of light,
    (c 3.0x108ms-1)

20
Wave Model
  • Wavelength (?) is the distance between successive
    waves measured in micrometers (1 ?m 1x10-6m).

21
Wave Model
  • Frequency (v) is the number of waves (cycles)
    passing a fixed point in a given period of time
    measured in cycles per second or hertz.

22
Wave Model
  • Wavelength and frequency are related to the speed
    of light as follows c ?v
  • ? c/v
  • v c/?

23
Particle Model
  • EMR is comprised of tiny particles (quanta)
    called photons travelling in a wave-like pattern
    at the speed of light
  • Intensity is proportional to number of photons
  • Total amount of energy is related to wavelength
    and frequency by Plancks constant (h)
  • Q hv
  • Q hc/?
  • where Q energy of a quantum

24
EMR
25
EMR and Remote Sensing
  • All RS systems obtain information by measuring
    and recording EMR received at the sensor
  • All objects interact (reflect, refract, absorb)
    with incident EMR differently
  • In addition, all objects above absolute zero (0º
    K) emit EMR directly proportional to their
    temperature

All RS systems discussed in this course deal
with the detection of EMR, however, there are RS
systems that are based on the detection of sound
waves, gravity, and electrical resistivity.
26
The Foundation of RS
  • Differences in how features interact with and
    emit EMR allow us to distinguish between objects
    based on their unique spectral characteristics or
    signatures
  • Variations are wavelength dependant some things
    may look the same at certain wavelengths but
    different in others

27
Radiance of EMR
  • A black body is hypothetical material that
    absorbs and re-radiates ALL incident EMR.
  • The Stephan-Boltzman equation describes the total
    amount of radiation emitted by a black body as a
    function of its surface temperature
  • M sT4
  • where M energy (Wm-2)
  • s Stephan-Boltzman constant
  • T temperature (K)

28
Total EMR Emitted
  • The higher the temperature the more total energy

Total Energy Area Under Curve
29
Wavelength of EMR Emitted
  • The higher the temperature the lower/shorter the
    wavelength of maximum radiance
  • Wein Law states that ?m A/T 
  • where A is a constant

Shortwave EMR
Longwave EMR
30
Atmospheric EMR Interactions
  • Atmospheric interactions include reflection,
    scattering and absorption of EMR
  • EMR that is not scattered or absorbed is simply
    transmitted through the atmosphere unaltered
    this is good
  • Some wavelengths of the EMS are so effectively
    scattered or absorbed that very little EMR
    reaches Earths surface this is bad

31
Transmission of EMR
  • Propagation of EMR through the material/object
    with no interaction
  • Path of EMR can be deflected or refracted as it
    passes through materials of differing density
  • Results in a change in velocity and wavelength
    but not frequency

32
Scattering EMR Interactions
  • Occurs when EMR bounces in all directions off
    gas molecules and particles in the atmosphere
  • Doesnt alter the incident EMR but may filter out
    a large proportion of it

33
Ralyleigh Scatter
  • Occurs when EMR is scattered by gas molecules and
    particles smaller than ?
  • Scattering is diffuse (in all directions) and ?
    dependent or selective
  • Scattering 1/ ?4

34
Mie Scatter
  • Occurs when EMR is scattered by particles larger
    than ?
  • Scattering is predominantly forward and is not ?
    dependent

35
Absorption of EMR
  • Occurs in atmosphere and at Earths surface
  • Incident EMR is typically converted to sensible
    heat energy and used to raise temperature of
    surface or object
  • Essentially, incident SW EMR is absorbed and
    reradiated as outgoing LW EMR
  • Absorption is wavelength dependent

36
Reflected EMR
  • Also occurs in atmosphere and at Earths surface
  • Two types of reflection dependent on roughness of
    surface or object

37
Specular Reflection
  • Incident EMR is reflected away from the surface
    like a mirror
  • angle of incidence equals angle of reflection.
  • Most common with smooth surfaces
  • Non-selective, all wavelengths are reflected
    equally
  • So no information about the object

38
Diffuse (Lambertian) Reflection
  • Occurs when incident EMR bounces off a material
    and scatters in all directions
  • Wavelength selective so diffusely reflected EMR
    does contain information about the character of
    an object
  • Most common when surface is rough compared to the
    ? of incident EMR

39
Surface Energy Balance
40
Overall Energy Balance
41
Where Do We Look ?
42
Spectral Signatures
  • Reflectance is wavelength dependent
  • Signatures represent average reflectance values
  • Signatures are spatially and temporally variable

43
Typical Spectral Signatures
44
Next TopicPhotographic PrinciplesChapter 2
Lillesand and Kiefer
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