Introduction to Remote Sensing Spatial, spectral, temporal resolutions Image display alternatives Vegetation Indices Image classifications Image change detections Accuracy assessment Satellites & Air-Photos
Selected RS Systems Landsat TM & Enhanced TM (Thematic Mapper) Ikonos & Quickbird MODIS (Moderate Resolution Imaging Spectrometer) Radarsat & ERS (European RS Satellite) SeaWiFS (Sea-Viewing Wide Field-of-View Sensor) GOES (Geostationary Operational Environ. Satellite) AVHRR (Advanced Very High Resolution Radiometer) SPOT (High Resolution Visible) Others
Digital Satellite Data Remote sensing: the acquisition of data about an object or area by a sensor that is physically far from the object or area. Digital satellite data is one type of remotely-sensed data aerial photography is another type of remotely-sensed geographic information Important advantage of remote sensing data: synoptic perspective: comprehensive view of large areas of the Earth s surface, vantage point of observation, digital format, multispectral, multi-temporal, multi-spatial.
Satellite Data - Benefits & Problems Benefits: it is already digital (unlike standard aerial photos) -- readily lends itself to manipulation and analysis to extract useful information synoptic perspective repeat coverage of areas minimal scale and geometric distortion problems relative to aerial photos Problems: generally low spatial resolution compared to aerial photos large data storage volumes distortions in data values due variations in atmospheric conditions, clouds, terrain, solar angle, etc... -- require preprocessing to correct!
Electromagnetic Spectrum (EMS) Visible Portion At a given Temperature, T 0.4 0.5 0.6 0.7 Cosmic Gamma X-rays UV Infrared Microwave Radio/TV Rays Rays Near/Medium/Thermal 10-6 10-4 10-2 1 10 2 10 4 10 6 10 8 Wavelength in Micrometers (= 10 3 nanometers) Increasing Wavelength Increasing Frequency and Energy
Passive (Optical) Sensor Technology Incoming EMR Reflected EMR Emitted EMR
Electromagnetic Radiation Spectrum Remote sensing satellites record data on electromagnetic radiation (EMR) satellites have detectors that record specific wavelengths in the EM spectrum EM radiation interacts with physical matter some wavelengths are absorbed & others reflected determine/estimate matter type by analyzing spectral signatures in satellite data
The Four RS Resolutions Satellite data characterized by four resolutions: spatial resolution: area on ground represented by each pixel (cell) in the satellite data. temporal resolution: how frequently a satellite platform obtains imagery of a particular area, orbital characteristics. spectral resolution: specific EM spectrum wavelength intervals captured/recorded by a particular satellite sensor. radiometric resolution: number of possible data values recorded/reportable by each satellite sensor, precision with which the EM spectral values are reported.
Aerial Photographs Scale = Focal Length/Flying Height Principal Point & Conjugate PP Radial Displacement Parallax Forward-Lap & Side-Lap Stereoscopic Analysis & Stereoscopes See photos for examples
Satellite Data - Pixel Brightness Values Brightness Value (BV) corresponding to intensity of EM radiation in specified spectral range detected for that pixel lower BV = lower level of EM radiation detected higher BV = higher level of EM radiation detected Displaying/viewing satellite data: high BV medium BV low BV For displaying/viewing satellite images: high BVs assigned bright/light color value low BVs assigned dark/dim color value
Satellite Data - Pixel Brightness Values & Display Landsat TM Multi-Spectral Display : RED GUN GREEN GUN BLUE GUN Band 4 - near infrared Band 3 - red visible Band 2 - green visible on-screen display: + + = Band 7 - middle infrared Band 4 - near infrared Band 2 - green visible on-screen display: + + =
Multispectral Composite Display Middle infrared (red gun), near infrared (green gun), green (blue gun): false color
Different Spatial Resolutions 1-2 m 30 m 79 m 1.1 km QuickBird, Landsat TM, Landsat MSS AVHRR IKONOS ETM
Daytona 500 Racetrack February 1995, NAPP (USGS EDC) grandstands racetrack Lake Lloyd
Digital Image Data MSS 1973 TM 1999 IKONOS 1999
Ikonos Images & Survey Sketch