pictures are worth a thousand words…
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Pictures are worth a thousand words…. 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. - PowerPoint PPT PresentationTRANSCRIPT
Pictures are worth a thousand words…
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
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, multi-spectral, multi-temporal, multi-spatial.
Remote sensing: the acquisition of data about an object or area by a sensor that is physically far from the object or area.
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)
0.4 0.5 0.6 0.7
Visible Portion
Cosmic Gamma X-rays UV Infrared Microwave Radio/TVRays Rays Near/Medium/Thermal
Increasing Wavelength
Increasing Frequency and Energy
At a given Temperature
, T
10-6 10-4 10-2 1 102 104 106 108
Wavelength in Micrometers (= 103 nanometers)
Incoming EMR
Reflected EMR
Emitted EMR
Passive (Optical) Sensor Technology
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 :
+ =+
Band 4 - near infrared Band 3 - red visible Band 2 - green visible on-screen display:
+ =+
Band 2 - green visibleBand 4 - near infraredBand 7 - middle infrared on-screen display:
RED GUN GREEN GUN BLUE GUN
Infrared band (4)
Red color gun Green color gun
Red band (3)
Blue color gun
Green band (2)
RGB Compositing Process
Panchromatic Display
Panchromatic display of a single band
Visible red (red gun), green (green gun), blue (blue gun) – “true”color
Multispectral Composite Display
Near infrared (red gun), red (green gun), green (blue gun): “false color”
Multispectral Composite Display
Middle infrared (red gun), near infrared (green gun), green (blue gun): “false color”
Multispectral Composite Display
1-2 m 30 m 79 m 1.1 km QuickBird, Landsat TM, Landsat MSS AVHRR IKONOS ETM
Different Spatial Resolutions
Daytona 500 RacetrackFebruary 1995, NAPP (USGS
EDC)
Lake Lloyd
grandstands
racetrack
Mt. St. Helens, May 1980Aircraft photo
The North Pole, June 1992 AVHRR
The Earth at Night, DMSP mosaic
Kuwait Oil Fires, April 1991Space Shuttle
Smoke Plumes from Oil Fires
Middle East Oil Fires, November 4, 2002
MODIS
Thermal (Far Infrared) People
SeaWiFS of Europe & UK:
particulate pollution in
southern UK and dust cloud
in southern Spain
GOES Image of Hurricane Bonnie August 25, 1998
SeaWiFS of Greenland
July 15, 2000
Washington, DC Bands 4, 3, 2 (infrared, red, green)
Landsat 7 Enhanced Thematic Mapper (ETM+)
GOES Image of Water Vapor: Thermal Infrared Sensing
SeaWiFS of Sea Surface Temperatures
IKONOS Multi-Spectral Imagery
Digital Image Data
MSS 1973
TM 1999
IKONOS 1999
Ikonos Images & Survey Sketch