Remote Sensing Fundamentals Slide Notes
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Outline
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Definition
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Common examples of remote sensing looking back into the 1600’s_telescope
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1800’s _ aerial photos and balloon campaigns
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1900’s pigeon flights as aircraft.
The Bavarian Pigeon Corps (1903)
Carrier pigeons were already a vital part of military communications, so why
not use them to for photo reconnaissance?
Balloons and kites were easy to shoot down, but pigeons were not. Small
light weight cameras were attached to the birds and a timer was set to take
pictures ever 30 seconds as it flew (note the bird's wing tips on the edges of
the photo in the lower right).
Hermann Krone (1827-1916) is one of the early practitioners of
photography in the German-speaking countries. Qualification as a
university teacher with the topic "On the use of light for illustration in the
service of science". A great number of landscape photographs. Krone
experiments and photographs with artificial lighting. Experiments in colour
photography. Publication of works on philosophy and natural sciences.
Preparation of a bill on photographic copyright
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Airplane aerial photos
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Some objects emit and absorb radiation better than others. A blackbody is an
object that absorbs all the electromagnetic energy that falls on the object, no
matter what the wavelength of the radiation. The wavelength is the distance
from wavecrest to wavecrest.
Electromagnetic radiation can be described in terms of a stream of
photons, which are massless particles each traveling in a wave-like pattern
and moving at the speed of light. Each photon contains a certain amount (or
bundle) of energy, and all electromagnetic radiation consists of these
photons. The only difference between the various types of
electromagnetic radiation is the amount of energy found in the photons.
Radio waves have photons with low energies, microwaves have a little more
energy than radio waves, infrared has still more, then visible, ultraviolet, Xrays, and the most energetic of all ... gamma-rays.
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The electromagnetic spectrum is a continuum of all electromagnetic
waves arranged according to frequency and wavelength. The sun, earth,
and other bodies radiate electromagnetic energy of varying
wavelengths. Electromagnetic energy passes through space at the speed of
light in the form of sinusoidal waves. Light is a particular type of
electromagnetic radiation that can be seen and sensed by the human eye, but
this energy exists at a wide range of wavelengths. The micron is the basic
unit for measuring the wavelength of electromagnetic waves. The spectrum of
waves is divided into sections based on wavelength. The shortest waves are
gamma rays, which have wavelengths of 10e-6 microns or less. The
longest waves are radio waves, which have wavelengths of many
kilometers.
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Many types of remote sensing systems_ sonar (submarines) There are two
basic types of sensors: passive and active sensors. Passive sensors record
radiation reflected from the earth's surface. The source of this radiation
must come from outside the sensor; in most cases, this is solar energy.
Because of this energy requirement, passive solar sensors can only capture
data during daylight hours. The Thematic Mapper (TM) sensor system on the
Landsat satellite is a passive sensor.
Active sensors require the energy source to come from within the
sensor. For example, a laser-beam remote sensing system is an active
sensor that sends out a beam of light with a known wavelength and
frequency. This beam of light hits the earth and is reflected back to the
sensor, which records the time it took for the beam of light to return. (ex.
Topography)
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Varieties of platforms are available.
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System components.
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Four properties for instrument design to achieve data goals.
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Spectral response depends on target – very useful way to determine the utility
of data bands to provide information on targets of interest.
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Radiometric Resolution
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Note water response
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Short for Picture Element, a pixel is a single point in a graphic image.
Graphics monitors display pictures by dividing the display screen into
thousands (or millions) of pixels, arranged in rows and columns. The pixels
are so close together that they appear connected.
The number of bits used to represent each pixel determines how many
colors or shades of gray can be displayed. For example, in 8-bit color
mode, the color monitor uses 8 bits for each pixel, making it possible to
display 2 to the 8th power (256) different colors or shades of gray.
On color monitors, each pixel is actually composed of three dots -- a red, a
blue, and a green one. Ideally, the three dots should all converge at the same
point, but all monitors have some convergence error that can make color
pixels appear fuzzy.
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The quality of a display system largely depends on its resolution, how
many pixels it can display, and how many bits are used to represent
each pixel. VGA systems display 640 by 480, or about 300,000 pixels. In
contrast, SVGA systems display 800 by 600, or 480,000 pixels. True Color
systems use 24 bits per pixel, allowing them to display more than 16
million different colors.
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Temporal need and value.
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Spectral resolution: Spectral resolution describes the ability of a sensor
to define fine wavelength intervals. The finer the spectral resolution, the
narrower the wavelength range for a particular channel or band.
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Note vis band delineation in color photo.
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Blue, green, or red only.
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Some features appear same, other different.
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NIR vs MIR
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What about TIR?
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What does that light and dark mixture mean?
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Brighter is warmer and darker cooler. Use Plank’s equation to derive surface
temperatures.
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Chart for future use.
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A great deal of current remote sensing at NASA and other agencies is
done via satellites in various orbits. Let’s talk about the types of orbits
and why they are important.
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Orbit determines … geographic range, temporal, day/night
opportunities.
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LEO
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MEO, often polar.
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HEO
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Geosynchronous
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GOES in GEoSYN orbit
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There are lots of uses of remote sensing data
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Classification based on features of interest using like features as a trainer.
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One kind of classifer
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LCLU classification examples using Landsat data in Atlanta
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Example Flooding
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Example Urban Sprawl in SF Bay
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Example LCLU Change Detection_Madison County Alabama
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Monitor weather
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Wildfires
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Sea surface temperature_key indicator for climate change events.
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Finish by briefly discussion Modis data.
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High spectral resolution, compared to GOES.