Transcript GIS for K-12 Education

Remote Sensing
• What is Remote Sensing?
• Sample Images
• What do you need for it to work?
• Electromagnetic Radiation
• Electromagnetic Spectrum
• Platforms – Things to consider
• Satellite Sensors
• Image Processing
•Analysis
What is Remote Sensing?
"Remote sensing is the science (and to some extent,
art) of acquiring information about the Earth's
surface without actually being in contact with it. This
is done by sensing and recording reflected or
emitted energy and processing, analyzing, and
applying that information." (CCRS)
• Aerial Photography – A whole discipline on its own
• Satellite Imagery – Includes information beyond the
visible spectrum. This is what we will focus on.
Advancements
http://www.classzone.com/books/earth_science/terc/content/investigations/esu101/esu101page01.cfm
Satellite Orbits
• Geostationary vs. Near Polar
• See animation
• Most satellite we will talk about
are Near Polar
Data Collection
Passive vs. Active
Passive Satellites: Satellites that record
reflected and naturally emitted energy from the
earth’s surface. (use the sun as energy source)
ACTIVE SATELLITES: Satellites that
send out their own source of energy to collect data
that is not naturally emitted from the earth’s
surface. It will record the amount of data reflected
back from earth.
This is a true color composite
This is a true color composite
This is a false color composite
This is a false color composite
Why the Strange Colors?
Stay tuned to find out!
How does it work?
A. You need some sort of energy
source: Naturally, this would be
light from the sun.
B. Interaction with atmosphere
C. Object that reflects, absorbs,
transmits energy.
D. You need a platform (satellite
sensor) that records the reflected
electromagnetic radiation.
E. You need a computer that can
process the electronic information
into an image.
F. You need a computer program and
individual who can interpret the
images.
Read the CCRS website
for a detailed tutorial of
remote sensing
Electromagnetic Radiation
This is the energy source provided by sun. This is the first
requirement for remote sensing to work.
Energy is emitted from the sun in the form of
electromagnetic radiation. Electromagnetic radiation is
emitted at various wavelengths. Objects on the earth
are sensitive to these different wavelengths. We call this
the electromagnetic spectrum. See next slide..
Electromagnetic Spectrum
Below is a good picture of the electromagnetic spectrum. You can see
examples of objects sensitive to different parts of the spectrum. Notice, the
visible part of the spectrum! This is what we see. But look at all of the other
information we cannot see at different wavelengths!
Electromagnetic Spectrum
Notice how small the visible part of the
spectrum is! This is the only part we
can associate with the concept of
COLOUR. Everything else has “no
colour”associated with it.
There is a lot of information at different
wavelengths and frequencies that we
cannot see. This is where remote
sensing is so valuable.
Violet: 0.4 - 0.446 mm
Blue: 0.446 - 0.500 mm
Green: 0.500 - 0.578 mm
Yellow: 0.578 - 0.592 mm
Orange: 0.592 - 0.620 mm
Red: 0.620 - 0.7 mm
(Wavelength is measured in metres (m)
or some factor of metres such as
nanometres (nm, 10-9 metres),
micrometres (mm, 10-6 metres) (mm, 10-6
metres) or centimetres (cm, 10-2 metres).
)
Short
Long
So What?….
The electromagnetic radiation hits the earth’s surface. What happens to it
when it hits? It can do three things:
Remote Sensing
deals with the part
that is reflected…
How much of the
electromagnetic
radiation is reflected
in each wavelength?
That is the question…
So What?….
Some things reflect more in parts of the electromagnetic spectrum
(or wavelength) then other parts. We call this the object’s
spectral signature….at what wavelength does it reflect most?
The more familiar you become with this, the more easily you
can interpret a remotely sensed image..
What do the
satellites do?
Sensors record
reflectance in each
different parts of the
spectrum (band) at
the same time.
A black and white
image is created for
each band…values
of 0-255 assigned.
What’s the problem?
Technology cannot
display all of this
information at once!
Image Processing
The result is a funny looking colourful image:
The more you know
about the spectral
signatures of
features, the more
you will understand
this image.
Image Processing
• Computers monitors can only
display colours using a combination
of red, green and blue dots.
– These dots of light originate from three
“Guns” at the back of the monitor.
These guns are called
CHANNELS in the
remote sensing world.
So, we can only display 3 BANDS of
information at once by displaying them
through the RED, GREEN, or BLUE
CHANNEL.
Analysis
• Band Combinations:
True Colour images (land cover
detection):
Image Red through Red Channel
Image Green through Green Channel
Image Blue through Blue Channel
True Colour
False Colour images (vegetation
detection):
Image Infrared through Red Channel
Image Red through Green Channel
Image Green through Blue Channel
False Colour
Platforms
How do the various satellite platforms use this information?
Below are some satellites in the sky right now. Each have
different characteristics in terms of spectral, spatial, and
temporal resolution.
•
•
•
•
•
SPOT
Landsat (TM)
RadarSAT
NOAA
ERS
NOAA
SPOT
RADARSAT
LANDSAT
ERS
Spectral Resolution
• Satellites Image in multiple bands:
SPOT XS 20m resolution
0.50-0.59µm - Visible Green
0.61-0.68µm - Visible Red
0.79-0.89µm - Infrared
LANDSAT (TM) 30m resolution
0.45-0.52µm Visible Blue
0.52-0.60µm Visible Green
0.63-0.69µm Visible Red
0.76-0.90µm Near Infrared
1.55-1.75µm Mid Infrared
10.5-12.5µm Thermal Infrared
2.08-2.35µm Mid Infrared
Spatial Resolution
What size are the pixels? What is the smallest object we
can see?
Temporal Resolution
How many times does the satellite take an image of the
same area? Important for change detection…
Don’t forget the satellites orbit and the earth orbits.
SPOT – 26 Days
LANDSAT – you find out!
RADAR – you find out!
Markets
Planning
Emergency
Response
Resource
Management
Environment
Agriculture
Sources
• CCRS website
• Virtual Hawaii website
• ESRI Canada