Using Synthetic Aperture Radar (SAR) to Map Natural Hazards and Disasters

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Using Synthetic Aperture Radar (SAR) to Map
Natural Hazards and Disasters

• Guest Scientist Jeffrey Weissel
• Originally presented 8 May 2004

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Remote Sensing of Our Planet

• During the last three or four decades, great
  advances have been made in technologies to study
  our planet from vantage points high above the
  surface
• Monitors aboard aircraft and satellites reveal
  much that cannot be discovered through
  surface-based techniques

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Remote Sensing E2C

• Christopher Small has shared examples of
  cutting-edge investigations using remote sensing
  over the years in E2C programs
• Some examples can be found at
• http//www.earth2class.org/workshops/ws5.htm
• http//www.earth2class.org/k12/w2_f2002/template.h
  tm

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• One of the best print resources about remote
  sensing is Claire L. Parkinsons
• Earth from Above Using Color-Coded Satellite
  Images to Examine the Global Environment
• University Science Books, Sausalito CA ISBN
  0-935702-41-5

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Todays Topic

• Synthetic Aperture Radar (SAR) is one of the
  most useful of the remote sensing strategies used
  by research scientists and operation specialists
  in a variety of fields.

Death Valley, CA
http//www.jpl.nasa.gov/radar/sircxsar/
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Whats SAR and How Can It Help Map Natural
Disasters and Hazards?

• Synthetic Aperture Radar is a space or airborne
  technology that provides high-resolution
  monitoring for environmental and military
  purposes in all weather or day/night conditions
• With SAR it is possible to obtain detailed
  information quickly that may be of great use in
  combating such natural disasters as wildfires,
  oil spills, ice and seas, etc.

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How Does SAR Work?

• Details are complex, but in a simplified version,
  we can say that SAR operates by sending out
  energy pulses at microwave wavelengths and
  measuring the precise time of the returning echo
  from a surface
• What makes SAR different is that it creates an
  extremely sharp beam over a wide area that
  enables high-resolution imaging
• The next slide represents the process.

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http//www.sandia.gov/radar/whatis.html
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Here is an example of a SAR image of a natural
environmental hazard
http//www.sandia.gov/radar/images/oilslick.jpg
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SAR is one type of imaging radar

• Many types of optical as well as radar remote
  sensing systems have been developed in the past
  few decades that have yielded vast amounts of
  data about our planet
• All radar systems basically transmit a pulse in
  the radio frequency part of the EM spectrum and
  capture part of the returning echo, as shown in
  the next slide

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http//southport.jpl.nasa.gov/
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Imaging radars produce an image in the flight
direction and for a distance on one side of the
flight path
http//southport.jpl.nasa.gov/
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SAR involves combining signals along the flight
path to synthesize a very long antenna, thus
improving resolution
http//southport.jpl.nasa.gov/
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SAR and related technologies have been used for a
wide variety of studies

• As long ago as 1978, imagers aboard SeaSAT were
  used to obtain unprecedented views of the upper
  ocean and sea ice
• Many of the Shuttle missions obtained SAR and
  other images to reveal new discoveries about our
  planet
• NASAs Jet Propulsion Laboratory has had a lead
  role in much of this work
• http//southport.jpl.nasa.gov/

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The US Geological Survey has also utilized remote
sensing for a wide variety of purposes

• Interferometric SAR (InSAR) can detect surface
  displacements on the order of centimeters
  associated with changes in groundwater levels,
  which has been very useful in drought and water
  resource studies
• http//ca.water.usgs.gov/program/desert/insar/

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As aquifers are depleted, surface subsidence
occurs. InSAR can identify even millimeter-scale
differences over time.
http//ca.water.usgs.gov/program/desert/insar/ex_s
antaclara/
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Wildfires in the Western US

• Inevitable part of the environment
• Expansion of human communities into forested
  areas increase risks
• Landslides and flooding in burned-out areas are
  major post-fire threats
• Need new technologies to identify potential as
  effectively as possible
• http//landslides.usgs.gov/html_files/wildfires/in
  dex.html

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Debris flow over I-70 in Colorado after 1994
South Canyon fire. Partially dammed Colorado
River.
http//landslides.usgs.gov/html_files/wildfires/in
dex.html
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With this background introduction, we will
take a break and get ready for our guest
scientist, Dr. Jeffrey Weissel. He will
discuss some of his research that has utilized
SAR to shed new insight about various natural
hazards and disasters.