climate and global change notes 5-1 observing climate - remote sensing remote sensing observations...
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Climate and Global Change Notes
5-1
Observing Climate - Remote Sensing
Remote Sensing Observations
Fundamental Principle
Satellite Remote Sensing ComponentsTypes of Sensing
Passive SensingActive Sensing
Fundamental PropertiesRadiometric ResolutionSpectral ResolutionSpatial Resolution
Science Concepts
Definition
Climate and Global Change Notes
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Observing Climate - Remote Sensing
View NOVA Mayan Movie
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Observing Climate - Remote Sensing
DefinitionScience and art of obtaining information about an object, area or phenomenon through an analysis of data acquired by a device that is not in direct contact with the area, object or phenomenon under investigation
Lillesand, Thomas M., and Ralph W. Kiefer, 1979, Remote Sensing and Image Interpretation, John Wiley and Sons, Inc., p. 1
What are some common examples of remote sensors?
Climate and Global Change Notes
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Observing Climate - Remote Sensing
History• Telescope invented by
spectical-maker Hans Lippershey (c1570-c1619) of Holland
• Galileo introduced the telescope to astronomy in 1609
- Limited magnification - up to 30 times - and a narrow field of view
- First to see the craters of the moon, discover sunspots, the four large moons of Jupiter, and the rings of Saturn
Galileo
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http://www-groups.dcs.st-and.ac.uk/
~history/Posters2/Galileo.html
Climate and Global Change Notes
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Observing Climate - Remote Sensing
History (Con’t)
• 1858 — First aerial (balloon) photographer Gaspard Felix Tournachon, also known as Nadar; picture of Paris
• 1903 — The Bavarian Pigeon Corps
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http://latteier.com/pigeoncam/
http://latteier.com/pigeoncam/
http://latteier.com/pigeoncam/
San Francisco from a kite, 1906
http://www.skyeyephotography.
com/history.htm
Climate and Global Change Notes
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Observing Climate - Remote Sensing
History (Con’t)
• 1908 — First photos from an airplane
First flight, Wright Bros., Dec. 1903
• 1909 — Dresden International Photographic Exhibition
• 1914-1918 — World War I
Climate and Global Change Notes
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Observing Climate - Remote Sensing
History (Con’t)
• Today — Many platforms
- Ground based
- Aircraft
- Space shuttle
- Satellite
Climate and Global Change Notes
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Observing Climate - Remote Sensing
Fundamental Principle
• Targets display discernible differences in emitted, reflected or transmitted energy
- Target appearance changes with the wavelength with which it is observed- Dissimilar targets have differing appearances in a single wavelength
(or band of wavelengths)
Data Types• Photographic - Record one frame
at a time on a physical medium
• Digital - Record brightness (intensity) and convert to digital value one pixel at a time
• Pixels - Picture elements
Climate and Global Change Notes
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Observing Climate - Remote Sensing
Satellite Remote Sensing Components
• Source of illumination
• Atmosphere
• Target
• Sensing system
• Data processing and analysis system
• Output product
Two Types of Sensing Systems
• Passive
• Active
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Observing Climate - Remote Sensing
Passive Sensing
• Satellite measures energy that is reflected, emitted or transmitted (i.e., not absorbed or reflected) from the object, i.e., after the radiation has interacted with the object- Human eye- Camera- Radiometer
• Passive scanning geometry measuring Earth’s emitted radiation
• Passive scanning geometry measuring Earth’s reflected solar radiation
Sensor ImageOutput
Processing & Analysis
Source of Illuminationand Target
Scattered Transmitted
Atmosphere
Absorbed
Source of Illumination
Sensor
Target
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Observing Climate - Remote Sensing
Passive Sensing (Con’t)
• Passive limb scanning geometry measuring atmosphere’s transmitted (not absorbed or reflected solar radiation
Sun
Atmosphere
Target
Source of Illumination Sensing System
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Observing Climate - Remote Sensing
Active Sensing
• Satellite emits energy and then measures return energy after the radiation has interacted with the Earth’s surface or atmosphere.
- Radar- Sonar- Laser
Sensor
ImageOutput
Processing & AnalysisTarget
Reflected Energy
Atmosphere
TransmittedEnergy
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Observing Climate - Remote Sensing
Four Fundamental Properties For Design
• Image depends on the wavelength response of the sensing instrument (radiometric and spectral resolution) and the emission or reflection spectra of the target (the signal).
- Radiometric resolution
- Spectral resolution
• Image depends on the size of objects (spatial resolution) that can be discerned
- Spatial resolution
• Knowledge of the changes in the target depends on how often (temporal resolution) the target is observed
- Temporal resolution
Climate and Global Change Notes
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Observing Climate - Remote Sensing
Radiometric Resolution
• Number of shades orbrightness levels at agiven wavelength
• Smallest change in intensity level that can be detected by the sensing system
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Spectral Resolution
• Example: Black and white image
- Single sensing device
- Intensity is sum of intensity of all visible wavelengths
Can you tell the color of the platform top?
How about her sash?
Observing Climate - Remote Sensing
0.4 m 0.7 m
Black & White Images
Blue + Green + Red
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Observing Climate - Remote Sensing
Spectral Resolution (Con’t)• Example: Color image
- Color images need least three sensing devices, e.g., red, green, and blue; RGB
Using increased spectral resolution (three sensingwavelengths) adds information
In this case by “sensing” RGB can combine toget full color rendition
0.4 m 0.7 m
Color Images
Blue Green Red
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Observing Climate - Remote Sensing
Spectral Resolution (Con’t)
• Example
- What do you believe the image would look like if you used a blue only sensitive film?
- What do you believe the image would look like if you used a green only sensitive film?
- What do you believe the image would look like if you used a red only sensitive film?
Climate and Global Change Notes
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Observing Climate - Remote Sensing
Spectral Resolution (Con’t)
• Example (Con’t)
- Blue only sensitive film
- Green only sensitive film
- Red only sensitive film
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Observing Climate - Remote Sensing
Spectral Resolution (Con’t)
• Example (Con’t)
- What do you believe the image would look like if you used a thermal infrared sensitive film?
Blinded in the darkness, he extended his arms, felt around for obstacles, both to avoid and to hide behind. The men wearing infrared monocular night-vision units, the lenses strapped against their eyes by means of a head harness and helmet mount, were doubtless also carrying handguns. The others had rifles fitted with advanced infrared weapon sights. Both allowed the user to see in total darkness by detecting the differentials in thermal patterns given off by animate and inanimate objects.
Ludlum, Robert, 2000: The Prometheus Deception, p. 96.
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Observing Climate - Remote Sensing
Spectral Resolution (Con’t)
• Example (Con’t)
- What do you believe the image would look like if you used a thermal infrared sensitive film?
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What do you see if you look in the thermal infrared wavelength, i.e., around 10 microns?
Visible range from 0.4 to 0.7 microns Infrared range around 10 microns
Heat - Energy Transfer (Con’t)
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Observing Climate - Remote Sensing
Spectral Resolution (Con’t)
• Example - Thermal infrared view
Note warmer objects are brighter
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Observing Climate - Remote Sensing
Spectral Resolution (Con’t)
• Example
- What do you believe the image would look like if you used near and middle infrared sensitive film?
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http://observe.arc.nasa.gov/nasa/education/reference/reflect/ir.html
Near and middle infrared wavelengths, wavelengths between the visible and the thermal infrared (~10 microns)
Climate and Global Change Notes
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Observing Climate - Remote Sensing
Spectral Resolution (Con’t)
• Example
- What do you believe the image would look like if you used near and middle infrared sensitive film?
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Observing Climate - Remote Sensing
Spectral Resolution (Con’t)• Spectral response depends on target
• Leaves reflect green and near IR
• Water reflects at lower end of visible range
IncidentRadiation
Reflected
Absorbed
Transmitted
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Observing Climate - Remote Sensing
Spectral Resolution (Con’t)
• Example of sampling wavelengths
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Observing Climate - Remote Sensing
Spatial Resolution
• 40 X 40
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Observing Climate - Remote Sensing
Spatial Resolution (Con’t)
• 80 X 80
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Observing Climate - Remote Sensing
Spatial Resolution (Con’t)
• 320 X 320
Image depends both onspatial resolution and on radiometric resolution of the optical instrument
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Observing Climate - Remote Sensing
Spatial Resolution (Con’t)• GOES sounder – temporal resolution every hour; spatial resolution (10 km)
• MODIS instrument on the polar orbiting platforms - up to four passes a day, two daytime and two nighttime; spatial resolution (1 km)
AQUA MODIS 24 JAN 2004 GOES LST 2 AM CST
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Observing Climate - Remote Sensing
Spatial Resolution (Con’t)
• In addition, MODIS observes 36 separate frequencies of radiation, ranging from visible to infrared. GOES detects only five frequencies.
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http://science.nasa.gov/headlines/y2004/09jan_sport.htm