Climate and Global Change Notes 5-1 Observing Climate - Remote Sensing Remote Sensing Observations Fundamental Principle Satellite Remote Sensing Components

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


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View NOVA Mayan Movie


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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?


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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

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

http://www-groups.dcs.st-and.ac.uk/

~history/Posters2/Galileo.html


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History (Con’t)

• 1858 — First aerial (balloon) photographer Gaspard Felix Tournachon, also known as Nadar; picture of Paris

• 1903 — The Bavarian Pigeon Corps





http://latteier.com/pigeoncam/



San Francisco from a kite, 1906

http://www.skyeyephotography.

com/history.htm


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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


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History (Con’t)

• Today — Many platforms

- Ground based

- Aircraft

- Space shuttle

- Satellite


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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


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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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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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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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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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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


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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?


0.4 m 0.7 m

Black & White Images

Blue + Green + Red


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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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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?


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• Example (Con’t)

- Blue only sensitive film

- Green only sensitive film

- Red only sensitive film


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- 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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- 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)

QuickTime™ and aTIFF (LZW) decompressor



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• Example - Thermal infrared view

Note warmer objects are brighter


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• Example

- What do you believe the image would look like if you used near and middle infrared sensitive film?



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)


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• Example

- What do you believe the image would look like if you used near and middle infrared sensitive film?


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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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• Example of sampling wavelengths


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Spatial Resolution

• 40 X 40


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Spatial Resolution (Con’t)

• 80 X 80


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• 320 X 320

Image depends both onspatial resolution and on radiometric resolution of the optical instrument


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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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• In addition, MODIS observes 36 separate frequencies of radiation, ranging from visible to infrared. GOES detects only five frequencies.



http://science.nasa.gov/headlines/y2004/09jan_sport.htm

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Climate and Global Change Notes 5-1 Observing Climate - Remote Sensing Remote Sensing Observations Fundamental Principle Satellite Remote Sensing Components