Geography 1010
Remote Sensing
Contact Information
• Dr. Craig Coburn
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Office: University Hall C-854
Phone: 317-2818
e-mail: craig.coburn@uleth.ca
Office Hours: 11-12:00 Tuesday, Thursday.
• Research Interests:
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Remote Sensing Instrumentation.
Digital Image Processing.
Bidirectional Reflectance.
Environmental Applications of Remote Sensing Technology.
Data Sonification.
Today’s Lecture
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What is Remote Sensing?
Remote Sensing in a Geographic Context.
Electromagnetic Radiation.
Spectral Signatures.
What is Remote Sensing?
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Sensing without contact.
Gathering data from a distance.
Fundamental to all sentient life forms.
Two principle senses – sight and sound.
Sight and sound have similar physiological and
psychological underpinnings.
Physiology of Remote Sensing
• Physiology.
– Data gathering instruments (Eyes – Ears).
– Instruments are sensitive to different frequencies.
• Sound is a longitudinal mechanical wave of any
frequency.
• Travels at a speed of 340 msec-1 at room
temperature at sea level.
• The human ear has receptors that can detect
sound frequencies raging from 20 vibrations to
20,000 vibrations per second.
Physiology of Remote Sensing
• Sight is similar to sound.
• Electromagnetic Energy.
• 299,792,458 msec-1 (vs.
340 msec-1 for sound).
• Involves sensing light at
different frequencies.
• The visible spectrum is
limited in frequency to
between 400 and 700 nm.
Psychology of Remote Sensing
• Sensor take input and pass them along to the
brain.
• The brain makes the interpretations and
connections.
• Stereoscopic vision and hearing…all a function of
the brain.
• Colour production for sight happens in the brain.
• Eye’s collect data – Brain produces information.
Remote Sensing in a Geographic
Context.
• Maps have a long human tradition as a method of
conveying geographic knowledge.
– Abstract, symbolic, universal language.
• Until recently we did not have complete mapped
coverage of the Earth.
– Mostly resolved in the 1600’s.
– Not “complete” until the early 1800’s.
– That’s only about 6 generations of human existence
with knowledge about the globe.
Remote Sensing in a Geographic
Context.
• Map making was a laborious task.
• Information from voyages of exploration
(exploitation?).
• Hand-drafted maps were very expensive and had
to be created by being there.
– Ground Surveys.
– Sailing.
Remote Sensing Development
• Someone invented the photographic process
(disputed time – inventor).
• Invention of photographic process allowed for
image collection for the first time.
• Able to collect “Bird’s Eye View” of many areas.
• Development pace increases exponentially in this
field.
Aerial Photography.
• First truly useful form of
remote sensing in
Geography.
• Photographs from
balloons and kites were
not captured for purely
Geographic purposes.
Aerial Photography
Boston – 1860.
Aerial Photography
• WW1 was the first time aerial photography was extensively
used for recording geography…human geography.
• Knowledge of enemy location is important.
Aerial Photography
• Airplanes are much more stable than balloons or
kites.
• Better chance of developing a clear picture.
– Planes at this point are not all that fast.
• Other platforms were also tried.
• Pigeons!
– I only wish I was joking.
– Animal rights were still 80 years in the future!
Pigeons??
Photography Types
San Francisco Earthquake - 1906
Making Maps…The Pigeons Retire.
• Mostly the domain of the military.
• Some photographs were taken from a vertical
perspective during WW1.
• If you piece them together they look like a map.
• Widely used tool for mapping (accuracy not all that
important at this point).
Mapping with Photo’s
Making Measurements.
• Photo mosaics were
useful, but they only give
you the overview and are
not accurate maps.
• In the late 1800’s the
development of the parlor
stereoscope was a source
of entertainment before
radio and TV were
invented.
Photogrammetry
• The science of taking precise measurements from
photographs.
• Took 80 years to make it useful.
• The most important development in map making.
• Very precise measurements can be taken from
stereoscopic images.
• Correct distortions, and you have a remote
mapping tool (heights, distances, areas).
Photogrammetry
• Removes ground survey as a map making
method.
– We still do some ground survey, but only of very small
areas.
• Canada at the forefront of this technology.
– Vertical aerial photography from Lethbridge starting in
1928.
– Large landmass – sovereignty.
• All topographic maps are produced using this
technology.
Colour and Remote Sensing
• B&W photographs are still commonly used today.
• Colour adds additional information.
• Most objects on Earth reflect and absorb different
wavelengths of EMR, producing colour.
• If things are different colours, then we can use
colour to tell them apart.
– First thought in automated mapping using RS.
• The reflectance/absorption pattern is called a
spectral signature.
Spectral Signatures
From Spectral Signatures to Images
• We don’t use all of the spectral information.
• Can’t display the continuous spectrum as an
image.
– Too much data.
– Difficult to interpret.
• Rely on using discrete bands of information.
• Select the relevant areas of greatest change.
Spectral signatures with TM bands
RGB Band Composite