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1 What s in a Pixel? A Primer for Remote Sensing What s in a Pixel Development UNH Cooperative Extension Geospatial Technologies Training Center Shane Bradt UConn Cooperative Extension Geospatial Technology Program Sandy Prisloe URI Cooperative Extension Geospatial Extension Program Greg Bonynge National Geospatial Technology Extension Network Greg Bonynge, Shane Bradt, Sandy Prisloe NOAA Coastal Service Center Coastal Remote Sensing Group Shan Burkhalter, Jennifer Dare Mark Finkbeiner Supported in part by The Institute for the Application of Geospatial Technology Objectives Learn basic elements of RS technology Learn about the spatial, spectral, temporal, expense, and other differences among commonly used sensors and data products Learn how RS data is being used in a variety of applications Learn where & how to acquire RS data July 24th 30th, 2010 What s in a Pixel Page 1

2 What is Remote Sensing One of the Geospatial Sciences Remote Sensing, Geographic Information Systems, The Global Positioning System(s), Geodesy, Surveying, Spatial Statistics, Cartography, and others Definition "Remote Sensing is the science and art of obtaining information about an object, area, or phenomenon through the analysis of data acquired by a device that is not in contact with the object, area, or phenomenon under investigation." Lillesand and Kiefer Remote Sensing and Image Interpretation Typical Remote Sensing Devices Eyes Ears Nose July 24th 30th, 2010 What s in a Pixel Page 2

3 What Will Be Covered Why should you care? How does it work? Learning the lingo: what you need to know to talk the talk Types of data Sample applications How do you get it? Today! Thursday! It s All About Perspective How we view things (sensors) and the area that we look at affects what we can see and what we can know synoptic views provide a general overview close up views provide finer detail ground-level, oblique and birds-eye views provide different perspectives sensors capture information we can t see It s All About Perspective July 24th 30th, 2010 What s in a Pixel Page 3

4 Up Close What s This? Or This? Or This? July 24th 30th, 2010 What s in a Pixel Page 4

5 Areal Perspective Synoptic View 1998 Digital Orthophoto SID compressed image 1 meter pixels Getting Closer 1998 Digital Orthophoto SID compressed image 1 meter pixels Closer Still 1998 Digital Orthophoto SID compressed image 1 meter pixels July 24th 30th, 2010 What s in a Pixel Page 5

6 You Are Here or You Will Be Holloway Commons 1998 Digital Orthophoto SID compressed image 1 meter pixels Add a Little Color and a Building Holloway Commons 2003 Digital Orthophoto SID compressed image 1 meter pixels Sharpen the Focus Holloway Commons 2005 Digital Orthophoto SID compressed image 1 foot pixels 1:2,500 July 24th 30th, 2010 What s in a Pixel Page 6

7 Zoom in Once More Be Sure to Wave! Holloway Commons 2005 Digital Orthophoto SID compressed image 1 foot pixels Oblique Perspective See The Heights Oblique Perspective See The Relief Coastal Marsh Photo courtesy of Joel Stocker July 24th 30th, 2010 What s in a Pixel Page 7

8 Aerial Perspective - See What s Hidden Aerial Perspective - See The Context Google Earth 3-D Perspective - Visualization July 24th 30th, 2010 What s in a Pixel Page 8

9 Temporal Perspective How have our communities and the landscape evolved over time? If current trends continue, what will our communities look like in the future? July 24th 30th, 2010 What s in a Pixel Page 9

10 Management Perspective - Infrastructure Credit: City of Cranston, RI What Will Be Covered Why should you care? How does it work? Learning the lingo: what you need to know to talk the talk Types of data Sample applications How do you get it? Today! Thursday! July 24th 30th, 2010 What s in a Pixel Page 10

11 Components of Remote Sensing 1. An energy source 2. A means to measure the intensity of the reflected or emitted energy 3. A means to store these data 4. A means to visualize the stored data 5. A means to interpret the stored data Passive Sensors A passive sensor records reflected or emitted energy. Usually, the energy source is the sun. Examples include aerial and satellite images. ETM+ Quickbird IKONOS SPOT Note: Photographs and image data are different. Photos are recorded on sensitized film whereas images are recorded as electronic data. Active Sensors (LiDAR) An active sensor generates a signal that travels from the sensor to a target and back. Information about the signal such as the reflected intensity, time of travel, etc. are recorded by the sensor. Examples include sonar, radar and LiDAR. July 24th 30th, 2010 What s in a Pixel Page 11

12 Sensors - See What We Can t Sensors - Measure What We Can t Benthic Mapping Sensors - Measure What We Can t ETM path 20, row 31 4/11/99 RGB=4,5,6 2X Thermal Plume July 24th 30th, 2010 What s in a Pixel Page 12

13 Sensors - Measure What We Can t Seasonal Temperature Variation September 1984 November 1987 Credit: Dr. John Mustard, Department of Geological Sciences, Brown 2007 University University of New Hampshire Sensors - Measure What We Can t Color Landsat image in the Sahara Desert with a SIR- A inset, which penetrates the dry sand far enough to map the bedrock below. It reveals a channeled subsurface topography, with river valleys that have been lost by desertification. Shuttle Imaging Radar Sensors - Measure What We Can t Forest Health RDACS Imagery courtesy of NASA Institute for Technology Development July 24th 30th, 2010 What s in a Pixel Page 13

14 What s in an Image An image is made up of a collection of pixels (picture elements) Each pixel records the data measured by a sensor at a geographic location Software can display and analyze these pixels We Use Pixels All the Time Common devices that display pixels: TV, computer screen, cell phone Common devices that record pixels: digital camera, desktop scanner, TiVO But these all record visible light, see the same things as our eye What s in a Pixel Part 1 } RGB values True color images store, for each pixel location, 3 numbers that represent the brightness of red, green and blue colors. The RGB brightness values are used by the computer to recreate the image so we can see it on the computer s display. July 24th 30th, 2010 What s in a Pixel Page 14

15 What s in a Pixel Part 2 Sensors can be designed to measure and record data in more than just RGB visible light. Many RS sensors measure RGB and near-infrared. In this case, each pixel records 4 values but the computer can only display 3 at one time. Pixels Store Numbers Software uses the numbers to display colors? Near-IR (band 4) Red (band 3) Green (band 2) Blue (band 1) S A TE L L I T E C O M PU T E R July 24th 30th, 2010 What s in a Pixel Page 15

16 Questions? July 24th 30th, 2010 What s in a Pixel Page 16