5-1 observing clima - remo sensing -...

Climate and Global Change Notes

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Observing Climate - Remote SensingRemote 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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Observing Climate - Remote Sensing

View NOVA Mayan Movie


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Observing Climate - Remote SensingDefinition

Science and art of obtaining information about an object, area orphenomenon through an analysis of data acquired by a device that is not indirect contact with the area, object or phenomenon under investigation

Lillesand, Thomas M., and Ralph W. Kiefer, 1979, Remote Sensing and Image Interpretation, JohnWiley and Sons, Inc., p. 1

What are some common examples of remote sensors?


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Observing Climate - Remote SensingHistory• Telescope invented by

spectical-maker HansLippershey (c1570-c1619) ofHolland

• Galileo introduced the telescopeto astronomy in 1609

- Limited magnification -up to 30 times - and anarrow field of view

- First to see the craters of the moon,discover sunspots, the four large moons of Jupiter, andthe rings of Saturn

Galileo

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

~history/Posters2/Galileo.html


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Observing Climate - Remote SensingHistory (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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Observing Climate - Remote SensingHistory (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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Observing Climate - Remote SensingHistory (Con’t)• Today — Many platforms

- Ground based

- Aircraft

- Space shuttle

- Satellite


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Observing Climate - Remote SensingFundamental 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 digitalvalue one pixel at a time

• Pixels - Picture elements


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Observing Climate - Remote SensingSatellite 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 SensingPassive 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 interactedwith the object- Human eye- Camera- Radiometer

• Passive scanning geometrymeasuring Earthʼs emittedradiation

• Passive scanning geometry measuring Earthʼsreflected solar radiation

Sensor ImageOutput

Processing & Analysis

Source of Illuminationand Target

Scattered Transmitted

AtmosphereAbsorbed

Source of Illumination

Sensor

Target


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Observing Climate - Remote SensingPassive Sensing (Con’t)• Passive limb scanning geometry measuring atmosphereʼs transmitted (not

absorbed or reflected solar radiation

Sun

Atmosphere

Target

Source of Illumination Sensing System


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Observing Climate - Remote SensingActive Sensing• Satellite emits energy and then measures return energy after the radiation

has interacted with the Earthʼs surface or atmosphere.

- Radar- Sonar- Laser

Sensor

ImageOutput

Processing & AnalysisTarget

Reflected Energy

AtmosphereTransmitted

Energy


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Observing Climate - Remote SensingFour 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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Observing Climate - Remote SensingRadiometric Resolution• Number of shades or

brightness levels at agiven wavelength

• Smallest change inintensity level that canbe detected by thesensing 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 µm 0.7 µm

Black & White Images

Blue + Green + Red


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Observing Climate - Remote SensingSpectral 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 µm 0.7 µm

Color Images Blue Green Red


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Observing Climate - Remote SensingSpectral 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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Observing Climate - Remote SensingSpectral Resolution (Con’t)• Example (Conʼt)

- 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, bothto avoid and to hide behind. The men wearing infrared monocular night-visionunits, the lenses strapped against their eyes by means of a head harness andhelmet mount, were doubtless also carrying handguns. The others had riflesfitted with advanced infrared weapon sights. Both allowed the user to see intotal darkness by detecting the differentials in thermal patterns given off byanimate 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)


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Observing Climate - Remote SensingSpectral Resolution (Con’t)• Example - Thermal infrared view

Note warmer objects are brighter


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- 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 infraredwavelengths, wavelengthsbetween the visible and thethermal infrared (~10 microns)


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- 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 SensingSpectral Resolution (Con’t)• Spectral response depends on target

• Leaves reflect green and near IR

• Water reflects at lower end of visible range


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Observing Climate - Remote SensingSpectral Resolution (Con’t)• Example of sampling wavelengths


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Observing Climate - Remote SensingSpatial Resolution • 40 X 40


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Observing Climate - Remote SensingSpatial Resolution (Con’t)• 80 X 80


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Observing Climate - Remote SensingSpatial 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 SensingSpatial 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 SensingSpatial Resolution (Con’t)• 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

5-1 observing clima - remo sensing -...

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