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

GEOGRAPHY 372Lecture 1 – Introduction to Remote Sensing26 January 2009

Lab Meetings • Section 0101 9 to 11 am, Thursday • Section 0102 11 am to 1 pm, Thursday

Lab Meetings This Week • 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 Textbook • Campbell, J.B., Introduction to Remote Sensing, 4th edition, The Gulford Press, 2007.

Class Web Page 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 Geography GEOG 372 – Introduction to Remote Sensing GEOG 472 – Principles of Remote Sensing GEOG671 – Remote sensing instrumentation and observing systems GEOG672 – Physical principles of remote sensing and land surface characterization Geog 788A – Seminar in Remote Sensing

Course Goals • 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 Structure • 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 Schedule • 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 Exercises • 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 Exercises • 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 Material At the end of each lecture, I will post a pdf file that contains • The figures, pictures, and tables used in that days lecture • A summary of the key points and concepts introduced during the lecture

Keys for success in GEOG 372 • Attend lectures and labs • Read assignment prior to class • During lectures, listen and synthesize information into key points • Review lecture materials and readings at the end of each week: keep up and make sure you understand key points and concepts • Ask questions!!! • Attend all labs and turn in assignments on time

Honor Code • 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 Points • Definition of remote sensing • Key elements of a remote sensing system • Definition of remote sensing (revisited) • Why remote sensing??? • Categories of remote sensors • Resolution and Remote Sensing • Key epochs or eras in remote sensing

Reading Assignment • 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? • 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? Definition 1 –Remote sensing is the acquiring of information about an object or scene without touching it through using electromagnetic energy • RS deals with systems whose data can be used to recreate images • RS deals with detection of the atmosphere, oceans, or land surface

Elements of a Remote Sensing System 3. Sensing Device 4. Data Recorder 5. Information Production System 6. Information Delivery System 2. Area or scene of interest 1. Information User

Basic Remote Sensing System Sun Camera System

Balloon Photo of Boston ca. 1860s

What is remote sensing? 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

Why Remote Sensing? • Electromagnetic energy being detected by remote sensors is dependent on the characteristic of the surface or atmosphere being sensed – • Remote sensing provides unique information • 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 • Remote sensors can continuously collect data • Reliable and consistent source of information

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

MODIS Sea Surface Temperatures

Ultraviolet (  < 0.4 m) Visible ( 0.4 m <  < 0.7 m) Reflected IR ( 0.7 m <  < 2.8 m) Emitted (thermal) IR ( 2.4 m <  < 20 m) Microwave ( 1 cm <  < 1 m) EM Spectrum Regions Used in Remote Sensing  = EM radiation wavelength

Thermal IR Sensors • 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

Microwave remote sensing instruments operate at wavelengths greater than 1 mm • Figure 1-18 from Elachi, C., Introduction to the Physics and Techniques of Remote Sensing, 413 pp., John Wiley & Sons, New York, 1987.

Radar systems operate in the microwave region of the EM spectrum Figure from Jensen

Categories of Remote Sensors Remote sensors are based on • Specific regions of the EM spectrum • The types of EM energy being detected • The source of EM energy, e.g., passive versus active sensors

Types of EM energy detected by remote sensors 3. Scattered EM energy Atmosphere 1. Reflected energy 2. Emitted EM energy 1. Reflected EM energy Earth surface

Categories of Remote Sensors Remote sensors are based on • Specific regions of the EM spectrum • The types of EM energy being detected • The source of EM energy, e.g., passive versus active sensors

Passive versus active systems • 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

6000º K emitted UV, Visible, Near IR Sensors Active Sensors Microwave, Visible scattered Thermal IR, Microwave Sensors reflected emitted 300º K emitted

Definition of resolution • 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 Resolution • The measure of the smallest distance between objects that can be resolved by the sensor

Figure 1-8 from Jensen

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

Figure 9 Spectral Bands in a Visible and Near IR Remote Sensor Sensor has 6 different bands or channels Each band has a center wavelength Each band has a width = spectral resolution

Spectral Resolution • 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

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