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Remote SensingGIS/Remote Sensing Workshop
June 6, 2013
Outline
•What is remote sensing?
• How do we practice remote sensing?
•Why do we use remote sensing?
Have you done remote sensing before?
What is Remote Sensing?
“The art and science of obtaining information about an object without being in direct contact with the object” (Jensen, 2000)
Remote Sensing of the Environment
• Observe the world through remote sensing
• Use technology to surpass the limits of the human eye
Courtesy: earthobservatory.nasa.gov
How does remote sensing work?
Electromagnetic Spectrum
Courtesy: science.hq.nasa.gov
Use of Electromagnetic Radiation
Courtesy: missionscience.nasa.gov, science.nasa.gov
Emission
Reflection
Radiati
on
Types of Remote Sensing and Technology
AerialPhotos
LiDAR Radar
Satellite Imagery
ACTIVE
PASSIVE
Brief History of Aerial and Satellite Imagery
• 1850s: Flight
•WW1 and WW2:Aerial Surveillance and Reconnaissance
• Post-WW2: Civilian Applications
• 1960: Space Age RS
• 2000: Public Remote Sensing
Image Basics
• Composed of pixels
• “picture elements”
• Smallest unit in an image, single-colored
• Sensor records electromagnetic radiation within the pixel’s area
• Cameras
• 3 Megapixels = 3,000,000 pixels
• 10 Megapixels = 10,000,000 pixels Courtesy: earthobservatory.nasa.gov
ResolutionSpatial
• Size of the smallest feature that the sensor can detect
• Refers to “pixel size”
• Worse resolution = Lower resolution
Courtesy: Jim Campbell, Introduction to Remote Sensing; USGS
Resolution
Temporal
• Length of time between sensor visits
Spectral
• Size of wavelength interval that the sensor can distinguish
March 2002 June 2002
Courtesy: NASA
Visualizing a Pixel Lab
Aerial Photography vs. Satellite Imagery
• Standard aerial imagery is RGB
• Color infrared photography records IR reflectance
• Satellite imagery is a digital composite of many images taken at the same place and time, each at a different wavelength
Red Green
Blu
eIR
?
Courtesy: NASA
Display of Colors in Satellite Images
• The computer displays images in 3 colors: Red, Green, and Blue. Every computer graphic contains a combination of these colors to include the entire visible spectrum.
• Satellite images contain much more information!
• How would you display non-visible radiation on a computer screen or in a photo? For example, what color would you make IR?
• Image users decide which wavelengths to display
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Digital Pixels
Analyst selects and combines 3 of the wavelengths for RGB color image
Sensor records the image reflectance for each wavelength
Red
Blue
Green
NIR I
NIR 2
NIR 3
False Color Images
Image Interpretation Clues
• Location
• Size
• Color
• Texture
• Shape
• Pattern
• Height/Depth
• Site AssociationCourtesy: earthobservatory.nasa.gov
Textur
e
Image Interpretation
Courtesy: USGS
Image Interpretation Lab
Why do we use remote sensing?Agriculture, Forestry, Range
Government
Geology Water Resources
Archaeology
Environment
Vegetation types
Land use Rock types Water boundaries
Ancient ruins and roads
Disaster damage
Crop area Regional Planning
Geologic units
Floods and floodplains
Non-invasive records
Mining and reclamation
Biomass Mapping Landforms Glaciers/Ice
Pollution
Veg health
Transportation planning
Water depth
Wildlife distributions
Soil conditions
Turbidity and circulation
Adapted from “The Landsat Tutorial Workbook” (NASA, 1982)
Worldwide Applications
Courtesy: eros.usgs.gov
