Transcript No Slide Title

Power Point Presentation adapted
by Claude Brun del Re
Canadian Space
Agency
Agence spatiale
canadienne
Natural Resources
Canada
Ressources naturelles
Canada
Geomatics for Educators
Geomatics
• Term originally created in Canada
• Geomatics is the science and technology of gathering,
analyzing, interpreting, distributing and using geographic
information. Geomatics encompasses a broad range of
disciplines that can be brought together to create a detailed
but understandable picture of the physical world and our
place in it. These disciplines include:
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Mapping and Surveying
Geographic Information Systems (GIS)
Global Positioning System (GPS)
Remote Sensing
Canada’s Role in Geomatics
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Canada exports ~ $300 million worth of geomatics products and services.
Growth rate of 15 to 20 per cent per year.
Demand for GIS products and services is expected to exceed $10 billion per
year.
Geomatics is one of the fastest-growing technology sectors and Canada is a
recognized leader, both in its development and in the provision of
Geomatics software, hardware and value-added services.
Natural Resources Canada-
– Geomatics Canada
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Canada Centre for Remote Sensing
Centre for Topographic Information
Aeronautical Charts & Technical Services
Legal Surveys & International Boundary Commission
Geodetic Survey
List examples of remote sensing technology in
your every day life
• Satellite weather maps
• Photos
• Ultrasounds
• CAT scans
• Speed radar
• x-rays
• Sonar (for ships, bats
or dolphin)
REMOTE SENSING
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Definition and Process
Target
Sensor
Platforms
Electromagnetic
Energy
• Interpretation
• RADARSAT
Remote Sensing - A Definition
Indirect (remote) observations (sensing)
Remote sensing is the science (and to some extent, art) of
acquiring image data and deriving information about the
Earth’s surface without actually being in contact with it.
Remote sensing will give information about an object called
a target
Who could give me two common sensors?
Our eyes
A camera
How does remote sensing work?
Far away from the target, on what we call a platform.
Here are some types of platform
• Satellite
• Balloon
• Space shuttle
• Ground base tower
• Aircraft
Remote Sensing Process
• Energy Source or Illumination (A)
• Radiation and the Atmosphere (B)
• Interaction with the Target or Surface
(C)
• Recording of Energy by the Sensor (D)
• Transmission, Reception, and
Processing (E)
• Interpretation and Analysis (F)
• Application (G)
Passive Sensor
• Passive sensors detect or “sense” reflected
solar radiation
What does a passive sensor need
to sense the earth?
Active Sensors
• Active sensors produce and receive their own
electromagnetic energy
They produce their own illumination and they
operate in the microwave region
Some Atmospheric Interactions
• Energy will interact with the atmosphere on its
way in and out
• Ozone, nitrogen, CO2 and water vapour affect
incoming energy
• Energy affected if wavelength is < or = the particle
size
• Atmospheric windows are
wavelengths not affected by
the atmosphere
Absorption
• Some substances absorb certain
wavelengths of energy
• UV rays absorbed by ozone
•LW IR and SW microwaves absorbed
by water vapour
•These wavelengths are not suitable
for remote sensing
Scattering
•Occurs when molecules are larger or
equal to wavelength
•Rayleigh scattering - selective
scattering (UV, Blue sky)
•Non-selective - scatters all visible
wavelengths (clouds)
Atmospheric Windows
Terrain Interactions
• Radiation that reaches the
Earth’s surface can be:
Absorbed (A);
Transmitted (T); and
Reflected (R).
• This will vary with the type
of object. The type of
interaction will depend on
the wavelength of the
energy and the material and
condition of the feature.
• Look at different objects, for
example an egg, a green
apple and a tomato.
Diffuse and Specular Reflectors
Diffuse
rough surface
Specular
smooth surface
Electromagnetic Energy
• Electromagnetic energy is used to illuminate
the target in remote sensing
• Electromagnetic spectrum:
0.003nm 0.03nm 0.3nm
3nm
30nm
0.3
m 3 m
30
m
300
 m 0.3cm
Radio
Infrared
Microwave
Longer wavelength
Visible
Ultra-Violet
X-ray
Gamma Ray
Shorter wavelength
3cm
30cm
3m
30m
Visible Spectrum
Visible Wavelegths
 Violet: 0.4 - 0.446 m
 Blue: 0.446 - 0.500 m
 Green: 0.500 - 0.578 m
 Yellow: 0.578 - 0.592 m
 Orange: 0.592 - 0.620 m
 Red: 0.620 - 0.7 m
The basic colours of light
IR and Microwaves
 Reflected IR:
0.72 m to 3.0 m
 Thermal IR:
3.0 m to 15 m
 Microwaves:
1 mm to 1 m
Visible / Infrared (VIR)
• Colours we perceive are combinations of
electromagnetic energy
• VIR (visible infrared) or optical sensors
capture energy reflected by targets in the
optical and IR wavelengths
• Each target reflects or emits these types of
energy in different amounts
Spectral Response
• Different objects reflect, absorb and
transmit energy in differing amounts
• An object also transmits, reflects, and
absorbs each wavelength differently
• Spectral responses enable us to identify
different objects on images
• An object’s spectral response may change
over time
Spectral Response - Leaves
• Chlorophyll absorbs
red and blue
• Reflects green
• Greenest in summer
• Internal leaf structure
reflects near IR
Bands or Channels
• Each sensor has a purpose (vegetation,
ocean, ice, weather)
• Certain wavelengths provide more
information about certain targets
• To perform their tasks, sensors on satellites
detect energy in very specific, narrow
bands or channels of electromagnetic
energy
Spatial Resolution
Fine Resolution
Coarse Resolution
Swath
• Total field of view
• Width of the image in
ground distance
• For satellites, varies
between 10s to 100s
of kilometres
Orbits
• Geostationary
Near-polar
sun-synchronous
GOES
• Geostationary Operational Environmental Satellite
• Operated by NOAA to for weather forecasting and
monitoring
• 5 spectral bands (green-red to infrared)
• Geostationary above the
equator at 75 degs E and W
• Resolution 1 to 4 kilometres
NOAA-AVHRR
• Advanced Very High Resolution Radiometer
• Used for meteorology and other applications (vegetation)
• Sun-synchronous, near-polar orbits
(830-870 km above the Earth)
• Ensure that data for any region
of the Earth is no more than
six hours old
• visible, near, mid infrared,
& thermal IR
• 3000 km swath,
1 to 4 km resoloution
Landsat
• Landsat-1 was launched by
NASA in 1972
• Landsat 7 was launched in 1999
• ETM (Enhanced Thematic
Mapper) 8 bands VIR and
Thermal IR
• 30 metre resolution
• 185 kilometre swath width
• Lots of archived data
• Near-polar, sun-synchronous
orbits - 705 km
SPOT
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Système Pour l’Observation de la Terre
French commercial satellites
SPOT 1 -1986
SPOT -2 operational, SPOT-4 just launched
Sun-synchronous, near-polar orbits at altitudes around 830
km
2 Sensors MLA and PLA
PLA - black and white
MLA - 3 visible bands (blue-green-red)
60 to 80 km swath
10 to 20 m resolution
RADARSAT-1
• Canada’s first earth
observation satellite
• Launched November 4, 1995
• Monitoring the Arctic (ice) is its main role
• Unique, flexible, “steerable” sensor
• Many swath width choices
• Many incidence angles available
RADARSAT-1
Repeat Cycle
Orbit Geometry
- 24 days
- Circular, Near polar
- 14 orbits per day
- Sun-synchronous
Coverage
Inclination
- Global: 4,5 days
- 98.6° (from the equator)
- North America: 3 days
- Arctic: daily
-Passes to the right of the
North Pole
Altitude
Period
- 798 km
- 100.7 Minutes
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New Small Sats
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1 to 5 metre resolution
All commercially built
IKONOS
Earlybird
QuickBird
RADAR
• RADAR is an acronym for RAdio Detection And Ranging
• A microwave (radio) signal is
transmitted towards the target
• The sensor detects the
reflected (or backscattered)
portion of the signal
RADAR Images
• Radar images “look” like black and white photographs
• Tones of gray correspond
to the amount of radar energy
that is returned to the sensor
• The stronger the backscatter
or the more energy that is
returned to the sensor, the
lighter that area or object will
appear on the final image
RADAR Reflection
• There are three general
types of reflection:
specular
diffuse
corner
calm
Advantages
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Own energy source (images anytime of day)
“Sees” through clouds (images anywhere)
Provides good view of topography
Sensitive to surface roughness
Provides information on moisture content
Disadvantages
• Side-looking geometry creates distortions
• Radar speckle
• Excessive loss of data in mountainous areas
due to shadows
Radar Sensors
• SEASAT - NASA 1978
– lasted only a few months
• ERS-1 - ESA 1991-95
– 30 metre resolution
• ERS-2 - ESA 1994
– 30 metre resolution
• JERS-1 - Japan 1992
– 18 metre resolution
What is an Image?
• Image is a visual view of the energy
reflected by the target
• Satellite images are digital: they are made up
of numbers usually from 0 to 255 where 0 is
black and 255 is white
• The numbers (radiance value) are arranged
in rows and columns
• Each square is called a PIXEL
• A number or a value of reflected energy is
stored for each pixel
Raster Data
• Images are stored as raster data - grid of cells
or pixels
• Each pixel represents a certain amount of
ground like 10 m x 10 m
• Each pixel is representative of the amount of
energy backscattered by the target
Pixels and Lines
• Upper left corner is the origin
• X values are pixels or columns
• y values are lines or rows
Pixels and Lines
Pixels
Lines
X
X= Pixel 2 and Line 2 ( 2, 2)
Bits and Bytes
• Bits are binary digits (0 or 1)
• Images are collected as 8, 16, 32 bit data
• Bit refers to the number of exponential levels
a binary digit is taken to
– single bit = 21
– 8 bit = 28 or 256 levels of grey
– 16 bit = 216 or 65536 levels of grey
Image File Formats
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.pix = PCI or Eoscape
.img = ERDAS Imagine
.lan = ERDAS
GeoTIFF .tiff = contains georeferencing info
TIF = requires header file for georeferencing
.bil, ,bsq, raw = flat raster, common format, needs header
file
• jpeg = common image format for the WWW, no
georeferencing information
• GRID = ESRI raster format
VIR Images
• Usually 3 bands loaded
• One band loaded alone
appears as a greyscale
• Each assigned a colour
gun (Blue, green, red)
• Together, 3 bands form
colour image