introduction tointroduction to remote sensingremote sensing

Introduction toIntroduction toIntroduction to Introduction to Remote SensingRemote SensingRemote SensingRemote Sensing

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OutlineOutline

Remote Sensing DefinedRemote Sensing Defined Remote Sensing DefinedRemote Sensing Defined ResolutionResolution Electromagnetic Energy (EMR)Electromagnetic Energy (EMR) TypesTypes

InterpretationInterpretation InterpretationInterpretation ApplicationsApplications ApplicationsApplications

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Remote Sensing DefinedRemote Sensing Defined

R t S i iR t S i i Remote Sensing is:Remote Sensing is:

“The art and science of obtaining information “The art and science of obtaining information about an object without being in direct contact about an object without being in direct contact with the object” (Jensen with the object” (Jensen 20002000).).

There is a medium of transmission involved.There is a medium of transmission involved.

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Remote Sensing:Remote Sensing: Remote Sensing:Remote Sensing:

the collection of information about Earth surfacesthe collection of information about Earth surfaces … … the collection of information about Earth surfaces the collection of information about Earth surfaces and phenomena using sensors not in physical contact and phenomena using sensors not in physical contact with the surfaces and phenomena of interestwith the surfaces and phenomena of interestwith the surfaces and phenomena of interest. with the surfaces and phenomena of interest.

We will focus on data collected from an overhead We will focus on data collected from an overhead perspective via transmission of electromagnetic perspective via transmission of electromagnetic radiation.radiation.

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Remote Sensing Includes:Remote Sensing Includes:

A) The mission plan and choice of sensors;A) The mission plan and choice of sensors;

B) The reception, recording, and processing of the B) The reception, recording, and processing of the signal data; andsignal data; and

C) The analysis of the resultant data.C) The analysis of the resultant data.

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Remote Sensing Process Components

Energy Source or Illumination (A)

Remote Sensing Process Components

Energy Source or Illumination (A)

Radiation and the Atmosphere (B)

Interaction with the Target (C)

Recording of Energy by the Sensor (D)

Transmission, Reception, and Processing (E)

Interpretation and Analysis (F)

Application (G)

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ResolutionResolution

AllAll remote sensing systems haveremote sensing systems have four typesfour types ofof AllAll remote sensing systems have remote sensing systems have four typesfour types of of resolution:resolution:

SpatialSpatial

SpectralSpectral

TemporalTemporal

RadiometricRadiometric

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SpatialResolution

High vs Low?High vs. Low?

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SpectralSpectralResolution

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Temporal Resolution

July 2 July 18 August 3

16 days

July 2 July 18 August 3

TimeTime

11 days

July 1 July 12 July 23 August 3

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Radiometric Resolution

6-bit range0 63

8-bit range0 255

10-bit range010 bit range

1023

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Electromagnetic SpectrumElectromagnetic Spectrum

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Aerial PhotosAerial Photos

Balloon photographyBalloon photography Balloon photography Balloon photography ((18581858))

Pigeon camerasPigeon cameras Pigeon cameras Pigeon cameras ((19031903))Kit h t hKit h t h Kite photography Kite photography ((18901890))

Aircraft (WWI and Aircraft (WWI and WWII)WWII) Images: Jensen (2000)))

Space (Space (19471947))

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Early days: Boston, from Tethered Balloon (1860)Development of air photography before airplanesDevelopment of air photography before airplanes

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Word War I: Air photos for preconnaisance from fighter planes and planes and pigeons

Balloons and kites were easy to shoot down, but pigeons were not Small light weight cameras were attached to the were not. Small light weight cameras were attached to the birds and a timer was set to take pictures ever 30 seconds as it flew 24

Oblique photos from mountain peaks: BanffOblique photos from mountain peaks: Banff

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Early topographic mapping from Early topographic mapping from mountain peaks:mountain peaks:mountain peaks: mountain peaks:

Canadian Rockies, Canadian Rockies, 18901890

PhotoPhoto--topography led by topography led by Edouard DevilleEdouard Deville

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Since 1945, all our topographic mapping is done from aerial photography: Air photos enabled a huge reduction in fieldwork costs, and an increase in how

i kl d t l l ld b d quickly and accurately large areas could be mapped

Athabasca Glacier, 1958 27

Photogrammetry: "the science of obtaining reliable measurements from photos"

Photo interpretation: "the identification and extraction of meaning of objects"objects

Photogrammetry needs a minimum 5 known point locations per photo

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Anaglyphs Anaglyphs –– 33D imageryD imagery

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Elements of Image InterpretationElements of Image InterpretationElements of Image InterpretationElements of Image Interpretation

Shape:Shape: Shape:Shape: Many natural and humanMany natural and human--made features have made features have

unique shapes.unique shapes.

Often used are adjectives like linear, Often used are adjectives like linear, l l ll l d ll l ll l d lcurvilinear, circular, elliptical, radial, square, curvilinear, circular, elliptical, radial, square,

rectangular, triangular, hexagonal, star, rectangular, triangular, hexagonal, star, g g gg g gelongated, and amorphous.elongated, and amorphous.

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Shape: the form of an object on an air photo helps to identify the object. Regular uniform shapes often indicate a human i l t involvement;

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ShapeShapeShapeShape

Jensen (2000)

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Size: a measure of the object's surface area(e.g. single-lane vs. multi-lane highways); (e.g. single lane vs. multi lane highways);

Time: temporal characteristics of a series of h h b h l f l dphotographs can be helpful in determining

the historical change of an area (e.g. looking at a series of photos of a city taken in p ydifferent years can help determine the growth of suburban neighbourhoods; 38

Pattern:Pattern: Pattern:Pattern: Pattern is the spatial arrangement of objects on Pattern is the spatial arrangement of objects on

the landscapethe landscapethe landscape.the landscape.

G l d i ti i l d d dG l d i ti i l d d d General descriptions include random and General descriptions include random and systematic; natural and humansystematic; natural and human--made.made.

More specific descriptions include circular, oval, More specific descriptions include circular, oval, curvilinear, linear, radiating, rectangular, etc.curvilinear, linear, radiating, rectangular, etc.

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Pattern: similar to shape the spatial arrangement of objects Pattern: similar to shape, the spatial arrangement of objects (e.g. row crops vs. pasture) is also useful to identify an object and its usage;

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PatternPatternPatternPattern

Jensen (2000)Jensen (2000)

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Elements of Image InterpretationElements of Image InterpretationElements of Image InterpretationElements of Image Interpretation Shadow:Shadow: Shadow:Shadow:

Shadow reduction is of concern in remote sensing Shadow reduction is of concern in remote sensing because shadows tend to obscure objects thatbecause shadows tend to obscure objects thatbecause shadows tend to obscure objects that because shadows tend to obscure objects that might otherwise be detected.might otherwise be detected.

However, the shadow cast by an object may be However, the shadow cast by an object may be the only real clue to its identity.the only real clue to its identity.y yy y

Shadows can also provide information on the Shadows can also provide information on the h i ht f bj t ith lit ti lh i ht f bj t ith lit ti lheight of an object either qualitatively or height of an object either qualitatively or quantitatively.quantitatively.

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ShadowShadow

Jensen (2000)

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Shadow: a shadow provides information about the object's height, shape, and orientation (e.g. tree species); height, shape, and orientation (e.g. tree species);

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Elements of Image InterpretationElements of Image InterpretationElements of Image InterpretationElements of Image Interpretation Tone and Color:Tone and Color:

A A bandband of EMR recorded by a remote sensing of EMR recorded by a remote sensing instrument can be displayed on an image in instrument can be displayed on an image in p y gp y gshades of gray ranging from black to white.shades of gray ranging from black to white.

These shades are called “tones” and can beThese shades are called “tones” and can be These shades are called tones , and can be These shades are called tones , and can be qualitatively referred to as dark, light, or qualitatively referred to as dark, light, or intermediate (humans can seeintermediate (humans can see 4040--5050 tones)tones)intermediate (humans can see intermediate (humans can see 4040 50 50 tones).tones).

Tone is related to the amount of light reflected Tone is related to the amount of light reflected from the scene in a specific wavelength interval from the scene in a specific wavelength interval (band).(band).

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Tone/Colour: the colour characteristics of an object, relative to other objects in the photo (e.g. sand has a bright tone, while water usually has a dark tone; tree species can be determined by the colour of their leaves a dark tone; tree species can be determined by the colour of their leaves at certain times of the year);

Monochrome(panchromatic) air (panchromatic) air photos are used more frequently as colour photography colour photography costs twice as much.

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Tone and ColorTone and Color

Jensen (2000)( )

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Elements of Image InterpretationElements of Image InterpretationElements of Image InterpretationElements of Image Interpretation Texture:Texture: Texture:Texture:

Texture refers to the arrangement of tone or color Texture refers to the arrangement of tone or color in an imagein an imagein an image.in an image.

Useful because Earth features that exhibit similar Useful because Earth features that exhibit similar tones often exhibit different textures.tones often exhibit different textures.

ff Adjectives include smooth (uniform, Adjectives include smooth (uniform, homogeneous), intermediate, and rough (coarse, homogeneous), intermediate, and rough (coarse, h t )h t )heterogeneous).heterogeneous).

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TextureTexture

Jensen (2000)

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Texture: the physical characteristics of an object affect texture (e.g. calm water has a smooth texture; a forest canopy has a rough texture); py g );

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Elements of Image InterpretationElements of Image InterpretationElements of Image InterpretationElements of Image Interpretation Height and Depth:Height and Depth:g pg p

As discussed, shadows can often offer clues to the As discussed, shadows can often offer clues to the height of objects.height of objects.g jg j

In turn, relative heights can be used to interpret In turn, relative heights can be used to interpret objectsobjectsobjects.objects.

In a similar fashion, relative depths can often beIn a similar fashion, relative depths can often beIn a similar fashion, relative depths can often be In a similar fashion, relative depths can often be interpreted.interpreted.

D i ti i l d t ll i t di t d h tD i ti i l d t ll i t di t d h t Descriptions include tall, intermediate, and short; Descriptions include tall, intermediate, and short; deep, intermediate, and shallow.deep, intermediate, and shallow.

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Height and DepthHeight and DepthHeight and DepthHeight and Depth

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Elements of Image InterpretationElements of Image InterpretationElements of Image InterpretationElements of Image Interpretation Association:Association: Association:Association:

This is This is veryvery important when trying to important when trying to i bj i ii bj i iinterpret an object or activity.interpret an object or activity.

AssociationAssociation refers to the fact that certain refers to the fact that certain features and activities are almost always features and activities are almost always yyrelated to the presence of certain other related to the presence of certain other features and activitiesfeatures and activitiesfeatures and activities.features and activities.

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Association/Site: associating the presence of one object with another, or relating it to its environment, can help identify the object (e.g. industrial buildings often have access to railway sidings; industrial buildings often have access to railway sidings;

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AssociationAssociation

Jensen (2000)

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Thank YouThank YouThank YouThank You

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introduction tointroduction to remote sensingremote sensing

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