1. 2 Campbell, Chapters 3 (3.1-3.8) and 5 (5.1 to 5.11) Unless otherwise noted, all images in this lecture are from Jensen, J.R., Remote Sensing of the

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Lecture 4

Photographic Systems, Aerial Photography, and Image InterpretationFebruary 11th 2009

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SyllabusLecture/Hourly Exam Schedule and Assigned Readings (Subject to Change)

Week Date Lecture Topic Reading Part I Remote Sensing Basics

1 26-Jan 1 Introduction to Remote Sensing Ch 1 28-Jan University Closed

2 02-Feb 2 Principles of EM radiometry and basic EM Theory Ch 204-Feb Principles of EM radiometry and basic EM Theory II

3 09-Feb 3 Atmospheric Influences on EM Radiation 11-Feb 4 Photographic Systems/Image Interpretation Ch 3,5

4 16-Feb 5 The Digital Image I Ch 4,1018-Feb The Digital Image II

5 23-Feb 6 Applications with areal and space photography 25-Feb Exam 126-FebLab 1 Introduction to ENVI – manipulation of digital imagery

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Campbell, Chapters 3 (3.1-3.8) and 5 (5.1 to 5.11)

Unless otherwise noted, all images in this lecture are from Jensen, J.R., Remote Sensing of the

Environment - An Earth Resource Perspective, 544 pp., Prentice Hall, Upper Saddle River, NJ, 2000.

Reading Assignment

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1. Components of a camera system2. Collection of aerial photographs 3. Categories of aerial photographs4. Photogrammetry5. Definition of image interpretation6. Reasons for using image interpretation7. Key elements of image interpretation

Lecture 4 Outline and Key Points

5Source of image from the internet

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Joseph Niepce – 1826Created first photographic image in FranceUsed a camera obscura, exposed the scene for

8 hoursPhotographic plate was made of pewter and

was coated by bitumen suspended in lavender oil

Bitumen is a tar like substance found in crude oil – today it is used in roofing tar and asphalt pavement

When exposed to light, bitumen/oil hardened and adhered to the pewter plate

Non-hardened areas washed away

Early pioneers in photography

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Emulsion layer

Base layer

Anti-halationlayer

Figure 5

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Emulsion layers – contain light sensitive particles (silver-halide crystals) suspended in gelatin

Base or support material (polyester or cellulose acetate)

Anti-halation layer – absorbs all light that gets through first two layers to prevent reflection back into the emulsion

Film Layers

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Based on three primary colors (red, green, blue)

When added together, these three primary colors produce white light

ACT is the basis for human vision and photographic systems

Additive Color Theory

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Color films have 3 emulsion layers – filters are used to expose the emulsion layers to different regions of the EM spectrum

0.4 to 0.5 m: blue region of the EM spectrum

0.5 to 0.6 m: green region of the EM spectrum

0.6 to 0.7 m: red region of the EM spectrum

0.7 to 1.1 m: near infrared region of the EM spectrum

Photographic films

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Aerial metric cameraFigure 6

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Throughout most of the 20th century, aerial camera systems used film to record information

Aerial cameras used black and white, color and color-IR film to record data

This changed in 1986, when Kodak invented the first charged couple device that was capable of sensing and recording an entire photographic image The first digital camera recorded 1.4 million picture

elements (pixels) in a 5 by 7 inch format

Now, digital aerial camera systems are quite common

Invention of Digital Cameras

18Digital Aerial Camera System from Vexcel Corp.

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Focal length (f) – is the distance, when the lens is focused on infinity from the center of the lens to the film or focal plane where the image is in focusWide angle lenses, have short focal lengthsTelescopic lenses have longer focal lengthsArea of coverage ~ 1 / f

Focal Length

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One can alter the focal length

of the lenses used in a camera system to vary

the area of coverage of the

system

Figure 9

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Relationship between aircraft altitudeand ground coverage – two ways to change FOV

a. Changing the focal length of the camera lens will alter the angular coverage of the system – as the focal length gets smaller, the angular coverage increases

b. As the angular cover increases (focal length decreases), the FOV increases

Figure 23

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Relationship between aircraft altitudeand ground coverage – two ways to change FOV

Changing the aircraft altitude will alter the ground coverage of the system

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Vertical Photograph Camera optical axis < 3° off vertical

Low-ObliqueCamera optical axis > 3° off verticalHorizon not in image

High ObliqueCamera optical axis > 3° off verticalHorizon in image

Categories of Aerial Photographs

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SR-71World’sFastest Aerial Camera Platform

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The science of making accurate measurements by means of aerial photographyRequires development of specific skills

What is Photogrammetry?

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Analogue photogrammetryVisual interpretation using hard copy

(photographs or transparencies)

Digital or analytical photogrammetryComputer analysis on digitized photography

What is Photogrammetry?

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The examination and analysis of images for the purpose of identifying objects and features and judging their importance

Image/Photo Interpretation

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1. Represents the fundamental process for human (visual) analysis of remote sensing imagery

2. Provides a unique spatial observation perspective

3. Provides information that cannot easily be obtained in other ways

4. Provides ability to do accurate mapping, including 3-D information

5. Can provide information beyond our visual perception range

6. Allows for change detection analyses of specific regions where satellite data are not available

Why is image interpretation such an important tool?

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38Image from -http://rs.gso.uri.edu/amy/avhrr.html

AVHRR Image of land and sea surface temperature from thermal IR radiance measurements

Red – warmestOrangeYellowGreenBlue Purple - coldest

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While human vision provides a unique perspective, it is a limited perspective

Humans primarily observe the world from a limited, ground-level view –vertical perspective

Aerial platforms allow the viewing of an area from a more synoptic, horizontal perspective

Unique perspective of aerial imagery – the aerial/regional perspective

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45Lillesand and Kiefer 2000Figure 4.32

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Can create a 3-D view using aerial photographs collected from slightly different vantage points

Using a stereoscope, allows an interpreter to view the earth’s surface in three dimensions

Extremely valuable for interpreting landforms and other 3-D features

Stereoscopic imagery can be processed to generate accurate 3-d maps (e.g., accurate in the x,y,z dimensions) of the earth’s surface

Stereoscopic viewing

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Monitoring Land Cover Change

1937

1955

1968

1990

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Analysis of the cartographic information in the image

Examination of image characteristics

Key Steps in Image Interpretation

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Analysis of image characteristicsSize (length, width, perimeter, area)ShapeShadowTone/colorPatternTextureSite/situation/association

Key Stepsin Image Interpretation

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Shape

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Shape

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The presence of a shadow provides important information on the relative positions of objects

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1. Provide information on relative height2. Contain indirect information on geometric

characteristics of some features3. Provide a unique means for interpreting

topographic features4. Areas that are in shadows lack information

4 important aspects of shadows

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BW photograph collected with Near infrared film

Image tone – variations in image tone (e.g., the grey scale from white to black) allow for discrimination of different forest cover types

Dark area is a pine stand and the light colored forests are deciduous trees

(see next slide)

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Vegetation Reflectance

00.050.1

0.150.2

0.250.3

0.350.4

0.450.5

300 400 500 600 700 800 900 1000

Wavelength (nanometers)

Refle

ctance

Maple Pine

Blue Green Red

Infrared

Maple trees have a brighter tone

Pine trees have a darker tone

Reflectance controls image tone

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Texture – characteristic placement and arrangement of repetitions of tone and color in an image

Pattern – systematic or random arrangement of discrete objects within a scene

Texture and Pattern

68Texture & Pattern

69Texture & Pattern

70Texture & Pattern

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Determining where an image was collected often provides key information on features within the image

Location provides context for interpreting an image

Importance of Location

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SyllabusLecture/Hourly Exam Schedule and Assigned Readings (Subject to Change)

Week Date Lecture Topic Reading Part I Remote Sensing Basics

1 26-Jan 1 Introduction to Remote Sensing Ch 1 28-Jan University Closed

2 02-Feb 2 Principles of EM radiometry and basic EM Theory Ch 204-Feb Principles of EM radiometry and basic EM Theory II

3 09-Feb 3 Atmospheric Influences on EM Radiation 11-Feb 4 Photographic Systems/Image Interpretation Ch 3,5

4 16-Feb 5 The Digital Image I Ch 4,1018-Feb The Digital Image II

5 23-Feb 6 Applications with areal and space photography 25-Feb Exam 126-FebLab 1 Introduction to ENVI – manipulation of digital imagery

Documents

1. 2 Campbell, Chapters 3 (3.1-3.8) and 5 (5.1 to 5.11) Unless otherwise noted, all images in this lecture are from Jensen, J.R., Remote Sensing of the