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Remote Sensing(?)

Remote Sensing-Derived GeospatialInformation

Remote Sensing is the observation of the Earth from satellites or aircrafts.

Sensors mounted on these platforms capture images of the Earth that reveal features may or may not apparent to the naked eye.

The end users or image analysts interpret the data, extract information, and use it to answer real world questions.

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Gaspard Felix Tournachon (1820-1910), a Parisian portrait photographer, was kneeling in a fragile balloon gondola.

He obtained the first aerial photograph from a tethered balloon in 1858 near Paris, France.

Tournachon patented the aerial survey as we known it today.

A portion of an aerial photograph of Downtown Boston, obtained by James W. Black and Samuel A. King from a tethered balloon 1,200 ft. above in October 13, 1860.

It is believed to be the first aerial photograph taken from a captive balloon in the U.S. and the earliest aerial photograph still exist.

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King commented in 1860 that:

“This is only the precursor, no doubt, of numerous other experiments; for no one can look upon these pictures, obtained by aid of the balloon, without be convinced that the time has come when what has been used for public amusement can be made to serve practical end.”

In 1903, Julius Neubronner patented a breast-mounted aerial camera for carrier pigeons.

The lightweight (approximately 2.5 oz) 70-mm camera for acquiring oblique photos.

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One of the Wright Brothers in an unpowered heavier-than-air glider at Kitty Hawk, NC, in 1902.

Orville Wright(1871-1948)

Wilbur Wright(1867-1912)

Orville Wright took the first successful heavier-than-air engine-powered flight on December 17, 1903, while Wilbur Wright running at wingtip. It lasted 12 seconds and covered 120 ft.

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During the WWI aerial photography was employed.

Aerial photo-reconnaissance played a significant role in WWII.

A 1943 photo shows the main classroom of the U.S. Navy’s Photographic Interpretation School in Washington D.C.

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Throughout WWII military photo interpreters provided critical photo-derived information for use in bombing industrial targets and for post-bombing appraisals of the damages.

Aerial photograph of a German railroad yard and photo-derived map.

An example of WWII use of aerial photographs for bomb damage assessment.

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Geologists learned much about how to interpret vertical aerial photographs as an aid to mineral prospecting.

Vegetation types were delineated for wise forest management pre-WWII.

Use of aerial photographs for inventorying wildlife.

Oblique aerial photograph for counting of an antelope band, just prior to the start of its fall migration.

Feb. 2011

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Oblique aerial photograph for counting of snow geese during a “fly-by” over marshes in Delaware. About 13,500 snow geese could be counted from the whole picture.

Multispectral techniques developed in 1950s.• Penetration of camouflage materials

Near-IRVisible light photo

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• Early detection of diseases and damages on vegetation

Black-White Photo Near-IR Photo

Historical Aerial Photograph in Rhode Island

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10/26/1951

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American Civilian Space Program

As the National Aeronautic and Space Act of 1958 passed, National Aeronautic and Space Agency (NASA) officially started business on October 1, 1958.

Space Age – 1957 …

Earth Observation Era – 2000 …

Remote Sensing Platforms and Sensors

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QuickBird Satellite Panchromatic Images (0.6-m Spatial Resolution)

Remote Sensing

A comprehensive definition:

Remote sensing is the art, science, and technology of obtaining reliable information about physical objects and the environment, through the process of recording, measuring and interpreting imagery and digital representations of energy patterns derived from non-contact sensor systems (Colwell, 1997).

Colwell, R.N., 1997. History and place of photographic interpretation, Manual of Photographic interpretation, W.R. Philipson (Ed.) 2nd Ed., Bethesda: American Society for Photogrammetry & Remote Sensing, 33-48.

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How Far Is Remote?

There is no clear distinction about how great the distance should be. It could be 1 meter, 100 meters, or > 1 million meters.

Remote Sensing vs. in situ Data Collection

In remote sensing sensor systems record energy levels, by electromagnetic radiation (EMR) , directly and indirectly reflected or emitted from the ground targets.

Most of the in situ data collection involves going out in fields and questioning the phenomena of interests.

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Remote Sensing: Advantages

1. Remote sensing is unobtrusive, i.e., a passive remote sensing does not disturb the object or area of interest.

2. Remote sensing devices are often programmed to collect data systematically (size, time…). This systematic data collection can remove sampling bias introduced in some in situ investigations.

3. Remote sensing can provide fundamental biophysical data, including: x,y location, z elevation or depth, biomass, temperature, moisture content, etc.

4. Remote sensing can cover large areas and some of the areas are very difficult or impossible in in situdata collection (wetland, forest, desert, …).

Remote Sensing: Limitations

1. Remote sensing provides some spatial, spectral, and temporal information of value. Data analysis is critical.

2. Human beings designed the sensors to collect data, specify resolutions, calibrate sensors, select platforms that carry sensors, determine when data will be collected, and specify how data are processed. Human-induced error will likely be involved.

3. Remote sensing data could be expensive to collect and interpret or analyze.

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Remote Sensing vs. Bird’s-eye View?

(vertical view vs. elevated view of an object from above with a perspective)

Instantaneous Field of View (IFOV)

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Vertical Aerial Photography

A vertical photography is obtained when the camera's optical axis is within 3o of being vertical (perpendicular) to the Earth's level surface.

Vertical Aerial Photography

A vertical photograph in conjunction with another overlapping vertical aerial photograph obtained from slightly different viewing position may be analyzed using quantitative principles to derive the following type of information:

• Accurate planimetric (x, y location) base maps of natural and man-made features.

• Topographic (z-elevation above sea level) base map• Raster digital elevation models (DEM)• Accurate orthophotographs (aerial photographs that

are geometrically accurate in x, y)

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Remote Sensing vs. Bird’s-eye View?

Oblique Aerial Photography

An oblique aerial photograph is obtained if the camera's optical axis deviates more than 3 degree from vertical.

Low oblique aerial photograph: the horizon is not visible. Visual interpretation of the photograph yields detailed information about the object.

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High oblique aerial photograph: horizon is visible.

Object with height appear to lean away from the person viewing the image. It may never be able to extract quantitative information from oblique aerial photograph.

Types of Aerial Cameras

Single-lens mapping cameras: obtain most of the aerial photography used to map the planimetric (x, y) location of features and to derive topographic (contour) maps.1. Narrow angle camera lens: < 60o

2. Normal angle camera lens: 60o - 75o

3. Wide-angle camera lens: 75o - 100o

4. Super-wide-angle: > 100o

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Types of Imageries

Black-and-White Imagery (film or digital)Panchromatic - sensitive to blue, green, and red lights. It produces gray tones that are expected and recognized by human beings.

Black-and-White Infrared Imagery (film or digital)Sensitive to near-infrared (NIR) spectrum. Records energy that is beyond our human perception. Certain tones might not represent what we would anticipate in the image.

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Black-and-White Infrared Imagery

Health green vegetation is dark on panchromatic photography because it absorbs almost 80-90% of the incident blue, green, and red radiant energy for photosynthetic purpose.

Conversely, healthy vegetation is bright on the black-and-white near-IR photography because it reflects 40-70% of the incident near-infrared energy.

Black-and-white panchromatic

Black-and-white near-infrared (IR)

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In a black-and-white panchromatic photograph vegetation is recorded in relatively dark tones because it absorbs much of the incident green and red energy.

A black-white near-infrared (IR) photograph depicts land-water interface well. Deciduous trees and tidal wetland vegetation are bright because healthy vegetation reflects much of incident near-IR energy.

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Panchromatic - blue Black-white Near IR

Normal / True Color ImageryRecords energy in the region from 0.47-0.7 m (blue, green, and red light) and depicts the terrain in the same colors as our eyes perceive the landscape.

Color-Infrared ImageryOriginally developed during World War II, when there was great interest in increasing the sensitivity of films in infrared region of the spectrum to detect camouflage.

Color IR records reflected energy from visible to near IR spectrum and can portray the energy in false colors.

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True Color Orthophoto

QuickBird Satellite

True-color and

False/pseudo-color Images

Concept of Multispectral

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Landsat True Color Imagery Landsat Pseudo Color Imagery

This is a natural color, high-resolution DigitalGlobe satellite image featuring the Golden Gate Bridge and Toll Plaza.

Image collected March 7, 2010

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This is an enhanced satellite image of the oil spill and clean up effort in the Gulf of Mexico. This image leverages the different sensor bands of WorldView-2 satellite to highlight the oil and dispersant. (Image collected June 15, 2010)

Unmanned Aerial Vehicle (UAV), or drone, is an aircraft with no pilot on board. UAVs can be remote controlled (e.g. flown by a pilot at a ground control station) or can fly autonomously based on pre-programmed flight plans.

UAV revolutionized the image acquisition capabilities.

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UAVs are capable of collecting very high spatial resolution images in flexible time windows, which provide a new avenue for monitoring fast changing environments.