GEOGRAPHY 372 Lecture 1 – Introduction to Remote Sensing 26 January 2009 1

GEOGRAPHY 372

Lecture 1 – Introduction to Remote Sensing

26 January 2009

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Lab Meetings2

Section 01019 to 11 am, Thursday

Section 010211 am to 1 pm, Thursday

Lab Meetings This Week3

Short meeting to review syllabus/policies etc., and also to tease out any technical difficulties. MANDATORY!!!

For those in Section 0101: We will meet this week from 10:00 – 11:00

For those in Section 0102: We will meet this week from 11:00 – 12:00

Course Textbook4

Campbell, J.B., Introduction to Remote Sensing, 4th edition, The Gulford Press, 2007.

Class Web Page5

All class materials will be placed on the Department of Geographies Courses Webpage:

http://www.geog.umd.edu/

Click onto Academics/Course Information/

Course Materials/GEOG 372

Summary of Remote Sensing Courses in the Department of Geography6

GEOG 372 – Introduction to Remote Sensing

GEOG 472 – Principles of Remote SensingGEOG671 – Remote sensing

instrumentation and observing systemsGEOG672 – Physical principles of remote

sensing and land surface characterizationGeog 788A – Seminar in Remote Sensing

Course Goals

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Provide the student with a basic understanding of the science and technology of remote sensing of the environment

Provide a strong foundation for GEOG 472 Enable the student to understand the

differences between the various satellite remote sensing systems that are in existence today

Enable the student to differentiate between the different types of information products generated from data collected by these systems

Introduce students to the basics of digital image processing

Lecture Structure8

Part 1 – Remote Sensing Basics Part 2 – Remote Sensing in the Visible

and Near IR Region of the EM Spectrum Part 3 – Thermal and Microwave Remote

Sensing

Lab Schedule9

There will be 9-10 full labs throughout the course of the term

Each lab will last 2 hours The first full lab will be during week 4 or

5

Grading – Lab Exercises10

Each lab is worth an equal proportion of your grade, though the number of questions may not be equal.

Lab exercises turned in late will not receive full credit.

Late Lab Exercises11

Up to 4 days late – 80% maximum 5 to 7 days late – 50% maximum 8 to 14 days late – 20% maximum > 14 days late – 0 credit

Policy on Lecture Material12

At the end of each lecture, I will post a pdf file that contains

1. The figures, pictures, and tables used in that days lecture

2. A summary of the key points and concepts introduced during the lecture

Keys for success in GEOG 37213

1. Attend lectures and labs2. Read assignment prior to class3. During lectures, listen and synthesize

information into key points4. Review lecture materials and readings at the

end of each week: keep up and make sure you understand key points and concepts

5. Ask questions!!!6. Attend all labs and turn in assignments on time

Honor Code 14

The University has a nationally recognized Honor Code, administered by the Student Honor Council. The Student Honor Council proposed and the University Senate approved an Honor Pledge. The University of Maryland Honor Pledge reads:

"I pledge on my honor that I have not given or received any unauthorized assistance on this assignment/examination.“

This honor code must be handwritten and signed on all assignments and exams.

Lecture 1 Outline/Key Points15

1. Definition of remote sensing2. Key elements of a remote sensing

system3. Definition of remote sensing (revisited)4. Why remote sensing???5. Categories of remote sensors6. Resolution and Remote Sensing7. Key epochs or eras in remote sensing

Reading Assignment16

Campbell, Chapter 1 Tatum, A.J., S.J. Goetz, and S.I. Hay, Fifty

years of earth observation satellites, American Scientist 96:390-398, 2008.

What is Remote Sensing?17

Remote sensing uses the radiant energy that is reflected, emitted, or scattered from the Earth and its atmosphere from various portions (“wavelengths”) of the electromagnetic (EM) spectrum – referred to as electromagnetic radiation

Our eyes are only sensitive to the “visible light” portion of the EM spectrum

What is remote sensing?18

Definition 1 – Remote sensing is the acquiring of information about an object or scene without touching it through using electromagnetic energy

a. RS deals with systems whose data can be used to recreate images

b. RS deals with detection of the atmosphere, oceans, or land surface

Lecture 1 Outline/Key Points19

1. Definition of remote sensing2. Key elements of a remote sensing

system3. Definition of remote sensing (revisited)4. Why remote sensing???5. Categories of remote sensors6. Resolution and Remote Sensing7. Key epochs or eras in remote sensing

Elements of a Remote Sensing System20

2. Area or scene of interest

3. Sensing Device

4. Data Recorder

5. Information Production System

6. Information Delivery System

1. Information User

Basic Remote Sensing System21

Sun Camera System

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Balloon Photo of Boston ca. 1860s

Lecture 1 Outline/Key Points23

1. Definition of remote sensing2. Key elements of a remote sensing

system3. Definition of remote sensing (revisited)4. Why remote sensing???5. Categories of remote sensors6. Resolution and Remote Sensing7. Key epochs or eras in remote sensing

What is remote sensing?24

Definition 2 – Remote sensing is the non-contact recording of information from the UV, visible, IR, and microwave regions of the EM spectrum by means of a variety of electro-optical systems, and the generation and delivery of information products based on the processing of these data

Lecture 1 Outline/Key Points25

1. Definition of remote sensing2. Key elements of a remote sensing

system3. Definition of remote sensing (revisited)4. Why remote sensing???5. Categories of remote sensors6. Resolution and Remote Sensing7. Key epochs or eras in remote sensing

Why Remote Sensing?

26 1. Electromagnetic energy being detected by remote sensors is dependent on the characteristic of the surface or atmosphere being sensed – Remote sensing provides unique information

2. Many portions of the earth’s surface and atmosphere are difficult to sample and measure using in situ measurements Only way to systematically collect data in

many regions

3. Remote sensors can continuously collect data Reliable and consistent source of information

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Moderate Burn All Years

y = 0.3299x - 18.268

R2 = 0.82

-18

-16

-14

-12

-10

-8

-6

-4

-2

0

0 10 20 30 40 50

6 cm % Volumetric Moisture

ERS-2 Backscatter (dB)

All Years

2003-4 Validation Sites

Linear (All Years)

Radar backscatter (image intensity) in burned forests is proportional to soil moisture

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31MODIS Sea Surface Temperatures

Lecture 1 Outline/Key Points32

1. Definition of remote sensing2. Key elements of a remote sensing

system3. Definition of remote sensing (revisited)4. Why remote sensing???5. Categories of remote sensors6. Resolution and Remote Sensing7. Key epochs or eras in remote sensing

EM Spectrum Regions Used in Remote Sensing

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1. Ultraviolet ( < 0.4 m)2. Visible ( 0.4 m < < 0.7 m)3. Reflected IR ( 0.7 m < < 2.8 m)4. Emitted (thermal) IR ( 2.4 m < <

20 m)5. Microwave ( 1 cm < < 1 m)

= EM radiation wavelength

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Thermal IR Sensors36

Thermal IR deals with the Far IR region of the EM spectrum, wavelengths between 2.4 and 20 um

Most Thermal IR scanners use wavelengths between 8 and 15 um

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Figure 1-18 from Elachi, C., Introduction to the Physics and Techniques of Remote Sensing, 413 pp., John Wiley & Sons, New York, 1987.

Microwave remote sensing instruments operate at wavelengths greater than 1 mm

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Radar systems operate in the microwave region of the EM

spectrum

Figure from Jensen

Categories of Remote Sensors

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Remote sensors are based on 1. Specific regions of the EM spectrum2. The types of EM energy being detected3. The source of EM energy, e.g., passive

versus active sensors

Types of EM energy detected by remote sensors

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1. Reflected energy1. Reflected EM energy

Atmosphere

2. Emitted EM energy

3. Scattered EM energy

Earth surface

Categories of Remote Sensors41

Remote sensors are based on 1. Specific regions of the EM spectrum2. The types of EM energy being detected3. The source of EM energy, e.g., passive

versus active sensors

Passive versus active systems42

Passive systems record energy that is emitted, scattered or reflected from natural sources, e.g., sunlight or emitted energy = f(the temperature of the surface or atmosphere being imaged)

Active systems provide their own source of EM radiation, which is then reflected or scattered, and this signal detected by the system

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6000º Kemitted

300º K emitted

UV, Visible, Near IRSensors

Thermal IR, MicrowaveSensors

Active SensorsMicrowave, Visible

reflectedemitted

scattered

Lecture 1 Outline/Key Points44

1. Definition of remote sensing2. Key elements of a remote sensing

system3. Definition of remote sensing (revisited)4. Why remote sensing???5. Categories of remote sensors6. Resolution and Remote Sensing7. Key epochs or eras in remote sensing

Definition of resolution45

Also referred to as resolving power Defined as the ability of a remote sensor

to distinguish between signals that are spatially or spectrally similar

Four types of resolution important in remote sensing – spatial, spectral, radiometric, temporal

Spatial Resolution46

The measure of the smallest distance between objects that can be resolved by the sensor

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Figure 1-8 from Jensen

Spectral Resolution48

Refers to the dimensions (widths) and wavelength regions of the EM spectrum to which a specific sensor is sensitive.

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Spectral Bands in a Visible and Near IR Remote Sensor

Sensor has 6 different bands or channelsEach band has a center wavelengthEach band has a width = spectral resolution

Figure 9

Spectral Resolution50

Most remote sensing systems collect data in 1 to 10 different wavelength regions or bands, each with broad width. e.g. Landsat 7 ETM+ 7 bands

Hyperspectral remote sensing systems have a large number of very narrow bands. e.g. MODIS 36 Bands

Radiometric Resolution51

The sensitivity of a remote sensing detector to variations in the intensity of the emitted, reflected or scattered EM energy that is being detected, e.g., the precision of the system

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One way to think of Radiometric Resolution

– how many different intensity levels can be discriminated by the remote sensor within a specific band?

Figure 10

Temporal Resolution53

How often a remote sensor has the ability to record data over the same area.

Lecture 1 Outline/Key Points54

1. Definition of remote sensing2. Key elements of a remote sensing

system3. Definition of remote sensing (revisited)4. Why remote sensing???5. Categories of remote sensors6. Resolution and Remote Sensing7. Key epochs or eras in remote sensing

Key Milestones in Remote Sensing

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1826 – Joseph Niepce takes first photograph1858 – Gaspard Tournachon takes first aerial photograph from a

balloon1913 – First aerial photograph collected from an airplane1942 – Kodak patents color infrared film1950s, 60s – First airborne thermal scanner, multispectral

scanner, high resolution synthetic aperture radar1960s – Corona satellite systems (cameras) initiated by the

Intelligence community , space photographs collected by astronauts

1960s, 1970s – Development of high speed computers and digital recording

1972 – ERTS-1 Launched – First Landsat satellite1980s – 2000s: Continued improvement in computer hardware

and software - processing speed - storage capacity and data management

1990s – Development of the internet and world wide web2000s – Routine production and delivery of information

products derived from satellite images

Elements of a Remote Sensing System56

2. Area or scene of interest

3. Sensing Device

4. Data Recorder

5. Information Production System

6. Information Delivery System

1. Information User

Remote Sensing Eras – Sensing Devices57

1830s 1920s 1950s

Simple camerasAerial cameras

Electro – Optical &

Microwave Systems

Remote Sensing Eras – Sensor Platforms58

1850s 1910s 1960s 2000s

Balloons

Aircraft

Spacecraft

UAV – UnmannedAerialVehicle

Remote Sensing Eras – Data recording and storage

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1830s 1960s/70s 1990s 2000sFilmBW/Color/Color IR

Digital Magnetic

tape

CD/DVD

MechanicalHard Drives Non-

MechanicalHardDrives

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Standard for data storage until late 1980s – 9 track tape drive – Cost $50,000

1 tape = 2400 ft long

Stored 50 Mb of informationCost of storage continues to drop

2002 – 100 Gigabyte drive = $2000

Today – 100 Gigabyte drive = $< 200

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Remote Sensing Eras – Data processing and analysis – production of information62

1830s 1970sVisual interpretation

Optical analytical devices

Computer aided digital

analyses

Remote Sensing Eras – Delivery of information to the end user

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1830s 1970s 1990s 2000sPhotographic products

Hand-drawn products

Computer

generated products

via digital tapes via the

internet

wired wireless

For Next Lecture…64

We’ll continue with remote sensing related material, but also cover: Exams, including material covered, grading

and dates Overall course grading Lab meetings