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GEOG 372 February 4 2009

GEOG 372 February 4 2009. What is remote sensing?. Definition 1 – Remote sensing is the acquiring of information about an object or scene without touching it through using electromagnetic energy RS deals with systems whose data can be used to recreate images

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GEOG 372 February 4 2009

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  1. GEOG 372February 4 2009

  2. What is remote sensing? Definition 1 –Remote sensing is the acquiring of information about an object or scene without touching it through using electromagnetic energy • RS deals with systems whose data can be used to recreate images • RS deals with detection of the atmosphere, oceans, or land surface

  3. Lecture 2 Continued The Basics of Electromagnetic Radiation (EM)February 4th 2009

  4. EM Radiation Particle Model -Radiation from Atomic Structures

  5. Wave Theory • Speed of light c = 3*108 m/sec • Wavelength = • Frequency= v • c = *v • v = c/ • = c/v

  6. Stefan-Boltzmann Law* The amount of EM radiation (M) emitted from a body in Watts m-2 can be calculated as M =  T4 Wien Displacement Law* • The wavelength with the highest level of emitted radiation (max) for an object of temperature T can be calculated as max = k / T

  7. Lecture Topics • Types of thermal energy transfer • Models of EM radiation/energy • Particle Model • Photon absorption, excitation, de-excitation • Wave Model • Characteristics of EM waves • Polarization, speed of light, wavelength, frequency • Laws governing EM radiation • Stephan-Boltzman Law • Planck’s Formula • Wien Displacement Law • Remote sensing in the visible and reflected infrared region of the EM spectrum • Maximum Solar Output Wavelengths λ • Examples of Visible & RIR λ Images • Basic Interactions of EM energy & the earths surface • Descriptors of EM radiation • Radiant flux • Radiant flux density – irradiance and exitance • Radiation budget equation • Reflection • Absorption • Transmission • Remote Detection of Exitance • Radiance

  8. Wavelength region for VI/ reflected IR remote sensing is between 0.4 and 2.6 m Figure 1 Reflected near and SW infrared Visible λ Reflected IR λ

  9. Incoming/Outgoing max = 2898/5880 = 0.49 mm max = 9.7 mm

  10. 92%

  11. Expand Information Express it Visually

  12. Lecture Topics • Types of thermal energy transfer • Models of EM radiation/energy • Particle Model • Photon absorption, excitation, de-excitation • Wave Model • Characteristics of EM waves • Polarization, speed of light, wavelength, frequency • Laws governing EM radiation • Stephan-Boltzman Law • Planck’s Formula • Wien Displacement Law • Remote sensing in the visible and reflected infrared region of the EM spectrum • Maximum Solar Output Wavelengths λ • Examples of Visible & RIR λ Images • Basic Interactions of EM energy & the earths surface • Descriptors of EM radiation • Radiant flux • Radiant flux density – irradiance and exitance • Radiation budget equation • Reflection • Absorption • Transmission • Remote Detection of Exitance • Radiance

  13. Reflected IR Region of EM Spectrum • 0.7 to 1.3 m – Near infrared • 1.3 to 2.8 m – Reflected Middle or Shortwave (SW) IR region

  14. False Color True Color

  15. Air Photo:Visible λcolor film, 1-2 m detailTimothyLake, OR

  16. Landsat 30 m Mt. St. Helens Mt. Adams RIR λ Columbia River

  17. AVHRR 1 km RIR λ Olympic Pen. Yellowstone N.P. Columbia River Mt. St. Helens

  18. Landsat 30m False Color Composite

  19. Space Shuttle 70 mm photo 5 m resolution Coral Reefs Bahamas

  20. Landsat 30m True Color λ

  21. Lecture Topics • Types of thermal energy transfer • Models of EM radiation/energy • Particle Model • Photon absorption, excitation, de-excitation • Wave Model • Characteristics of EM waves • Polarization, speed of light, wavelength, frequency • Laws governing EM radiation • Stephan-Boltzman Law • Planck’s Formula • Wien Displacement Law • Remote sensing in the visible and reflected infrared region of the EM spectrum • Maximum Solar Output Wavelengths λ • Examples of Visible & RIR λ Images • Basic Interactions of EM energy & the earths surface • Descriptors of EM radiation • Radiant flux • Radiant flux density – irradiance and exitance • Radiation budget equation • Reflection • Absorption • Transmission • Remote Detection of Exitance • Radiance

  22. Key components of VIS/RIR remote sensing 2. Energy emitted from sun based on Stephan/Boltzmann Law, Planck’s formula, and Wein Displacement Law 1. Sun is EM Energy Source VIS/NIR Satellite 6. EM energy detected by a remote sensing system EM energy 3. EM Energy interacts with the atmosphere 5. EM Energy interacts with the atmosphere 4.EM energy interacts with the Earth’s Surface

  23. Lecture Topics • Types of thermal energy transfer • Models of EM radiation/energy • Particle Model • Photon absorption, excitation, de-excitation • Wave Model • Characteristics of EM waves • Polarization, speed of light, wavelength, frequency • Laws governing EM radiation • Stephan-Boltzman Law • Planck’s Formula • Wien Displacement Law • Remote sensing in the visible and reflected infrared region of the EM spectrum • Maximum Solar Output Wavelengths λ • Examples of Visible & RIR λ Images • Basic Interactions of EM energy & the earths surface • Descriptors of EM radiation • Radiant flux • Radiant flux density – irradiance and exitance • Radiation budget equation • Reflection • Absorption • Transmission • Remote Detection of Exitance • Radiance

  24. Radiant Flux -  • The fundamental unit to measure electromagnetic radiation is radiant flux -  •  is defined as the amount of energy that passes into, through, or off of a surface per unit time • Radiant flux () is measured in Watts (W)

  25. Definition of a Watt (FYI – I won’t ask about these definitions on exams) • Newton - force required to cause the mass of one kilogram to accelerate at a rate of one meter per second squared • Joule - the amount of energy exerted when a force of one newton is applied over a displacement of one meter • Watt – one joule / second

  26. Radiant Flux Density Radiant flux density is simply the amount of radiant flux per unit area Radiant flux density represents the amount of EM energy coming from the area represented by a pixel  Radiant flux density =  /area

  27. Irradiance and Exitance Irradiance is the radiant flux energy that strikes a surface Exitance is the radiant flux density coming from a surface 

  28. Irradiance - I  Irradiance is the amount of incident radiant flux per unit area to strike a plane surface in Watts/square meter (W m –2 ) I Fig 2-20 in Jensen

  29. Exitance - M  • Exitance is the amount of radiant flux per unit area leaving a plane surface in Watts per square meter (W m –2 ) Fig 2-20 in Jensen

  30. Lecture Topics • Types of thermal energy transfer • Models of EM radiation/energy • Particle Model • Photon absorption, excitation, de-excitation • Wave Model • Characteristics of EM waves • Polarization, speed of light, wavelength, frequency • Laws governing EM radiation • Stephan-Boltzman Law • Planck’s Formula • Wien Displacement Law • Remote sensing in the visible and reflected infrared region of the EM spectrum • Maximum Solar Output Wavelengths λ • Examples of Visible & RIR λ Images • Basic Interactions of EM energy & the earths surface • Descriptors of EM radiation • Radiant flux • Radiant flux density – irradiance and exitance • Radiation budget equation • Reflection • Absorption • Transmission • Remote Detection of Exitance • Radiance

  31. Radiation Budget Equation Three things can happen to incident EM energy [i] when it interacts with a feature • Reflected • Absorbed • Transmitted i The degree to which EM energy is reflected, transmitted, and absorbed is dependent on the wavelength of the EM energy & the characteristics of the material the EM energy is interacting with

  32. Reflectance, Absorption, &Transmittance • Reflectance (r) is the ratio of incident EM radiation that is directly reflected from a surface of an object: r = r / i • Absorption () is the ratio of incident EM that is absorbed by the object:  = a / i • Transmittance () is the ratio of incident EM radiation that is transmitted through an object:  = t / i

  33. Reflectance r

  34. Absorption α

  35. Transmittance τ

  36. i (λ)= r(λ)+ t (λ) + a (λ) i (λ)= Incident Energy r (λ)= Reflected Energy a (λ)= Absorbed Energy t (λ)= Transmitted Energy

  37. Radiation Budget Equation* i = r+ t + a r is the amount of energy reflected from the surface ais the amount of energy absorbed by the surface tis the amount of energy transmitted through the surface

  38. Lecture Topics • Types of thermal energy transfer • Models of EM radiation/energy • Particle Model • Photon absorption, excitation, de-excitation • Wave Model • Characteristics of EM waves • Polarization, speed of light, wavelength, frequency • Laws governing EM radiation • Stephan-Boltzman Law • Planck’s Formula • Wien Displacement Law • Remote sensing in the visible and reflected infrared region of the EM spectrum • Maximum Solar Output Wavelengths λ • Examples of Visible & RIR λ Images • Basic Interactions of EM energy & the earths surface • Descriptors of EM radiation • Radiant flux • Radiant flux density – irradiance and exitance • Radiation budget equation • Reflection • Absorption • Transmission • Remote Detection of Exitance • Radiance

  39. For a VIS/RIR remote sensing system, the surface characteristic being detected is the result of reflectance from the earth’s surface VIS/RIR Remote Sensor The sensors only detect reflected EM radiation from a certain direction and in certain wavelength regions

  40. In remote sensing, we are not interested in all exitance, but only that exitance in the direction of the satellite system Because of diffuse scattering, there is exitance in all directions from a surface

  41. Detection of Exitanceby a remote sensing system Satellite Radiometer θ – Sensor viewing angle Area as seen by the sensor (projected area) = A cos θ A = area on ground being sensed

  42. RadianceSolid angle of the sensor a Flux from a surface is actually being emitted or reflected in all directions equally, i.e., it is being distributed into a hemisphere d The radiometer intercepts a fraction of the exitance from a surface, this fraction is defined by the solid angle, Ω, of the sensing system, which can defined by the area of the detector surface (a) and the distance to the target area (d) Ω = a/d

  43. Space Shuttle Limb Photographs Before Mt. Pinatubo Eruption After Mt. Pinatubo Eruption

  44. SyllabusLecture/Hourly Exam Schedule and Assigned Readings (Subject to Change) Week Date Lecture Topic Reading Part I Remote Sensing Basics 1 26-Jan 1 Introduction to Remote Sensing Ch 1 28-Jan University Closed2 02-Feb 2 Principles of EM radiometry and basic EM Theory Ch 2 04-Feb Principles of EM radiometry and basic EM Theory II3 09-Feb3 Atmospheric Influences on EM Radiation 11-Feb 4 Photographic Systems/Image InterpretationCh 3,54 16-Feb 5 The Digital Image I Ch 4,10 18-Feb The Digital Image II5 23-Feb 6 Applications with areal and space photography 25-Feb Exam 1 26-Feb Lab 1 Introduction to ENVI – manipulation of digital imagery

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