Sources of Geographic InformationWhat is Remote Sensing?Two Types of Remote SensingSolar RadiationLight and ColorSolar Electromagnetic RadiationEarly Remotely Sensed ImagesObtaining Remotely Sensed Images for Large AreasRemote Sensing - A Critical Source of IntelligenceRemote Sensing During WW IICold War Photo ReconnaissanceHigh Altitude Reconnaissance AircraftAVIRIS ER-2 ImageryThe Cuban Missile CrisisSatellite Remote SensingCivil Remote SensingGOES Hurricane ImageryThe Limitations of FilmThe Limitations of FilmThe Limitations of FilmDigital Remote SensingWhat is Digital Remote Sensing?Analog-to-Digital ConversionDigital ImagesMultispectral Remote SensingMultispectral Remote SensingHow Do We Display Multispectral Image Data?Color ArithmeticImage Display - Single BandImage Display - Single BandImage Display - Single BandImage Display - Multi-BandImage Display - Multi-BandDavid Tenenbaum – GEOG 070 – UNC-CH Spring 2005•Data properties: Spatial data, i.e. data that are associated with geographic locations•Data format: digital (analog data for traditional paper maps)•Data Inputs:•sampled from the real world•digitizing from paper maps•produced by government agencies, e.g. census bureau, USGS, USFS, state government, etc.•space or airborne remote sensing(NASA, NOAA, commercial, etc.)Approximately 80% of the duration of many large scale GIS projects is concerned with data input and managementSources of Geographic InformationDavid Tenenbaum – GEOG 070 – UNC-CH Spring 2005• Remote sensing is the science and art of obtaining information about a target, through the analysis of data acquired by a device that is not in contact with the target under investigation• We routinely use remote sensing when we see things:• Our eyes can see thing around us, and sometimes even far away from us • We can identify what we see as objects (e.g. blackboard, door, desks, etc.) • Why can we see? Because of the sunlight (or light from light bulbs) reflected off objects to the nerve cells in our retinae. However, our eyes can only see a narrow range of solar radiation within a large spectrumWhat is Remote Sensing?David Tenenbaum – GEOG 070 – UNC-CH Spring 2005• In remote sensing, the medium that usually carries the information is electromagnetic radiation. Using various sensors, we can collect the electromagnetic radiation in any portion of the spectrum. Based on the source of the energy, remote sensing can be broken into two categories:• Passive remote sensing: The source of energy collected by sensors is either reflected solar radiation (e.g. cameras) or emitted by the targets (thermal imaging).• Active remote sensing: The source of energy collected by sensors is actively generated by a man-made device. Examples include radar (which uses microwave energy) and LIDAR (LIght Detection Imagery And Ranging, which uses a laser).Two Types of Remote SensingDavid Tenenbaum – GEOG 070 – UNC-CH Spring 2005Electromagnetic radiation energy: Wave-particle dualityparticleWavelength (λ)• EMR energy moves at the speed of light (c): c = f λ• f = frequency: The number of waves passing through a point within a unit time (usually expressed per second)• Energy carried by a photon: ε = h f [h=Planck constant (6.626×10-34Js)]• The shorter the wavelength, the higher the frequency, and the more energy a photon carries. Therefore, short wave ultraviolet solar radiation is very destructive (sunburns)Solar RadiationDavid Tenenbaum – GEOG 070 – UNC-CH Spring 2005• Our visual system not only allows us to identify objects; we also see things in color; this provides us additional information about the objects we see• For example: We can distinguish between a bananathat is green (not ripe nor ready to eat) from a banana that is yellow (that is ripe and ready to eat)• The natural light we see can be described using seven colors, which can be remembered using the acronym ROYGBIV: R = Red, O = Orange, Y = Yellow, G = Green, B = Blue, I = Indigo, V = Violet• These colors were identified by Sir Isaac Newton with a prism in 1672: His research helped launch the era of modern opticsLight and ColorDavid Tenenbaum – GEOG 070 – UNC-CH Spring 2005Atmospheric windowsSolar Electromagnetic Radiation•The sun emits EMR across a broad spectrum of wavelengths:But the atmosphere blocks much of the energy before it reaches the surfaceDavid Tenenbaum – GEOG 070 – UNC-CH Spring 2005•M. Joseph Nicephore Niepce produced the very first permanent photograph (remotely sensed image) in 1826. He used a camera obscura and a metal plate coated with asphalt. The exposure lasted eight hours, taken through an open window at his courtyardPeartreeBarnroofEarly Remotely Sensed Images•Beyond what we see with our eyes, we need remotely sensed images that we can record and show to others:David Tenenbaum – GEOG 070 – UNC-CH Spring 2005•Geographic applications of remote sensing require that the camera be suspended high above the target to obtain remotely sensed images for large areas•Doing so required the means to suspend cameras in the airObtaining Remotely Sensed Images for Large Areas• Progress in aviation and remote sensing platforms:1. Pigeons2. Balloons3. Gliders4. Aircraft 5. SatellitesDavid Tenenbaum – GEOG 070 – UNC-CH Spring 2005•Like many technologies, remote sensing was initially developed for military applications. It became a critical source of military intelligence for the two World Wars and the Cold War, and it remains a critical source of intelligence•Knowing where enemy forces are deployed ahead of timeis crucial intelligence to help win a battle•World War I: On August 22, 1914, British reconnaissance aerial photography revealed a major change in direction of the German forces advancing on Paris. This timely information allowed the Allied army to fortify its position on the Marne River and hold off the German advance to ParisRemote Sensing - A Critical Source of IntelligenceDavid Tenenbaum – GEOG 070 – UNC-CH Spring 2005•Remote sensing played a significant role in WW II. In 1938, Werner von Fritsch, Chief of the German General Staff, predicted that “the nation with the best photo-reconnaissance will win the next war”•Photo identification of German invasion barges in canals near France in the summer of 1940 constituted the major evidence that an invasion of England would take place in less than 48 hours. The British launched