Remote Sensing Week 3
Remote Sensing Week 3 GEOG 2107
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This 4 page Class Notes was uploaded by Ivana Szwejkowski on Friday September 16, 2016. The Class Notes belongs to GEOG 2107 at George Washington University taught by Engstrom, R in Fall 2015. Since its upload, it has received 3 views. For similar materials see Intro to Remote Sensing in Geography at George Washington University.
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Date Created: 09/16/16
Remote Sensing week 3 9/12 Spatial resolution = instantaneous point of view x height of image sensor Temporal Spectral Radiometric Image Interpretation Interpreter Requirements Vision (stereoscopic acuity, color vision) Knowledge of application and environment Pattern recognition skills Intelligence and motivation Performance Tests Standardized Tests for screening -Recognition of Basic patterns and shape -See in stereo -Normal color vision Interpretive Elements Info contained in image data Scale dependent and interrelated Elements Elements of Interpretation- Tone/Color Basic elements of interpretation Amount of energy returned from object or location Amount of energy returned depends on- reflectance of object, sensitivity of sensor Black and White (Panchromatic), tone is greyness level ranging from black (high return) to white (low return) Color imagery- differences in color are based on energy returned in specific wavelength bands -Three dimensional tone varying in -Intensity- brightness -Hue- dominant wavelength/color -Saturation-purity of color Characteristic Placement and arrangement of repetitions in tone or color; subtle changes in tone in close proximity Visual impressions of roughness or smoothness Scale dependent Elements of Interpretation Size of interpretation Measured in two ways; Relative (compare two objects size) and Absolute ( known dimensions to scale) Shape -Top-down view versus profile -Cultural Features-tend to have regular geometric -Natural features- Patterns -Drainage Networks -Orchards -Housing Patterns -Road Networks Shadow -can aid analysis -can hinder analysis Height -absolute measurements versus oblique image data Context -highest level of cognition, integrates all levels of interpretation -Site and Association 9/14 Image interpretation continued Interpretation process Search procedure and interpretation keys Image information Location, date, sensor, spatial resolution Collateral (ancillary) data General to specific - Overall impression - Major geographic regions- natural vs. cultural - Approximate area of land cover/use - Grid system to describe location of features in image - Identify specific features - Examination of evidence within image to converge to interpretation Human vs. Automated Approaches Humans generally utilize higher order elements of interpretation, e.g. context, shape, size, more successfully than computer- qualitative Computers can quantify multiple levels of image tone more accurately than human- quantitative Computers are less biased, but may be less accurate because of limited ability for higher order interpretation Training and equipment Hybrid approaches Electro-magnetic Radiation (EMR) -Link between surface and sensor Sun Surface Sensor Energy Flow: Radiation Energy transferred between objects in the form of electromagnetic waves/ particles (light) Can occur in a vacuum Two Models- Wave & Particle Wave Theory Explains EMR transfer as a wave Waves travel through space at the speed of light 3 x 10^8 ms/2 Wave Properties- Amplitude Height of the wave crest above the undisturbed position Wave Properties- Wavelength - Lambda - Distance between successive crests or troughs - Micrometers - EMR Spectrum ( Gamma, X-Ray, UV, Visible, Reflected IR, Thermal IR, Microwave, Radio Wave Properties- Frequency -Hertz -Number of wave forms passing through a given point per unit time - Cycles s/2 Wavelength & Frequency = speed of light 3X10^8 m/s C= wavelength X frequency Relationship; inversely related Quantum Theory - Wave theory doesn’t account for all properties of EMR - Interaction of EMR with matter (absorption, emission) - EMR is transferred as discrete particles (photons) Planck’s Law; energy of a photon Q=hv Q= energy of quantum in Joules h= Planck’s constant Js v= frequency of EMR wave in Hz Energy Levels All objects above -273 C emit electromagnetic energy Energy radiated is a function of temperature Stefan-Boltzmann (SB) Law- describes emitted radiation from a blackbody as a function of temperature Radiation (Wm^-2) =SB constant X Temperature (K) Energy Levels: total energy emitted is proportional to T^4 Wien’s Displacement Law - Used to identify frequency of maximum energy emission - Inversely related to temperature EMR: Interaction with the Atmosphere - Must pass through twice - Energy detected by sensor is a function of Surface properties and Atmospheric influences - Scattering - Absorption EMR Transmission -Energy propagated directly through the atmosphere -Low transmittance with clouds and greenhouse gasses
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