This page includes the outline text from the classroom PowerPoint presentation, together with selected graphics from that presentation. The graphics will appear when the title hotlink is activated.

A copy of the classroom presentation, in .pdf format, can be downloaded from here.

Textbooks referred to are:

McLean and Gribble: Geology for Civil Engineers; [NB this segment is not represented in MG.]
Dennen and Moore: Geology and Engineering (DM)
Waltham: Foundations of Engineering Geology (W)
Lillesand and Kiefer: Remote Sensing and Image Interpretation

Portions of this display are illustrated with images from Small Blue Planet - The electronic Satellite Atlas, from Now What Software.

Remote Sensing

The science and art of obtaining information about an object, area, or phenomenon through the analysis of data acquired by a device that is not in contact with the object, area, or phenomenon under investigation.

• Use of electromagnetic spectrum
  • near-visible part of spectrum
  • surface-imaging techniques
• Broad definition includes most/all of Geophysics, but normally considered separate field

• Uniformity of image over large areas confers advantage for some applications
• Example is enhanced, low-visible-light (night-time) image of Antarctica from satellite platform
• Literal snapshot of weather pattern

Device Camera Sensor
Recording Medium Film Electronic
Processing Chemical Computing
Product Photograph Imagery
Display Stereoscope Screen/Print
Interpretation Human!

• Source - Sun (blackbody radiator)
• Spectrum at detector is altered by
  • Transmission losses
    • scattering, absorption
  • Reflection losses at surface
  • Scattering losses at surface
• Last two are source of information

• Energy may be reflected, transmitted, or absorbed by materials making up surface
  • reflection depends on composition of surface
• Energy may be diffused by rough surface
  • diffusion depends on scale of roughness

• Different materials respond differently across spectrum - including beyond-visible
• Additional information available in infra-red, thermal, radar bands of spectrum
• All these (and black-and-white) might be used if appropriate

• Both Physics and Geometry affect response
• "Ground Truth" establishes effect on spectrum in particular area
• Ground Truth work very important, because actual spectrum is usually a composite

• Next image is natural-colour image of volcano
• Surface/rock colours show texture from topography
• Little discrimination possible

• Distinctive colour change
• Information from IR band displayed as "Red" colour
• Explanation needs ground investigation
  • (probably younger lava flows, weathering differences)

Common Imaging System Types:

• Airborne Photography
  • b/w, colour, near infra-red
• Airborne Imagery
  • thermal infra-red, radar
• Satellite Imagery
• colour, near infra-red, thermal infra-red, radar

• Light reflected/diffused from individual area ("pixel") 10-80 m square focussed on individual detector, through filter
• Detector output is electronic, digital
• Each pixel may drive multiple filter/detector channels

• Aperture scanned to build up image (compare TV)
• Image reconstructed by computer/camera system
• Separate image possible for each channel (that is, each filtered part of spectrum)

• Image displayed in "false colour"
• Red, Green, Blue colours assigned to selected channels and mixed
• Choice of channel depends on application
• More complex imaging possible

Landsat Thematic Mapper

(Thanks to Daniel Pérez for supplying a correction to this screen).

• Brazil example shows resolution using false-colour

"blue" is recent clearing
"orange" is recent regrowth
"red" is old-growth forest

• Evaluation is consistent across scene

• Next visual page shows

"blue" (near-IR) snow
"red" (thermal band) basalt outcrop
"green" vegetation
"purple" (mid-IR) agriculture

• Direct measurement of surface temperature possible
• Resolution to fractions of Celsius degree is possible
• Information may come from temperature distribution itself
• Heat capacity (strongly dependent on water content) also mappable from thermal information

• Hunters Point Power Station, CA
• Land image from Thematic Mapper bands 1, 2, 3
• Water image from IR band 8
• Image shows distribution of heated wastewater from power station (temperature range < 5 Celsius degrees).

• Radiometer measures energy radiated from surface
• Version of thermal band on Landsat TM satellite
• Next image is mosaic, shows response of Advanced Very High Resolution Radiometer
• Unsubtle changes due to change in conditions for different parts of mosaic

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