Transcript www.crssa.rutgers.edu

Fundamentals of
Remote Sensing:
Digital Image
Analysis
Advanced Remote Sensing:
Introduction to Digital Image Analysis
Lecture 1
Prepared by R. Lathrop 10/99
updated 9/03
Readings:
ERDAS Field Guide 5th ed
ERDAS CH. 1: 1-15; 3: 52-77
Center for Remote Sensing and Spatial Analysis, Rutgers University
Lecture Notes 1: Overview of Remote Sensing
A number of these slides were originally
produced by Scott Madry and Chuck
Colvard with some subsequent
modification by Rick Lathrop. Additional
slides were produced by Rick Lathrop.
Center for Remote Sensing and Spatial Analysis, Rutgers University
Remote Sensing
• “Remote sensing is 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”.-Lillesand & Kiefer (1987)
Center for Remote Sensing and Spatial Analysis, Rutgers University
Radiation source/target/sensor
Electromagnetic energy interacts with
physical matter in different ways in
different parts of the spectrum.
Some energy is scattered, absorbed, etc.
Center for Remote Sensing and Spatial Analysis, Rutgers University
Digital Image Acquisition & Analysis
• Digitization of analog aerial photography, can be
very useful for historical studies and/or for high
spatial resolution needs
• Direct acquisition using some form of digital
imaging sensor
• Computerized image analysis can help to enhance
and extract information content of imagery in a
time-efficient, cost-effective manner
• Computers still can not replace the human image
analyst
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Aerial Cameras
A large format oblique
camera
Keystone’s Wild RC10 mapping camera
Aerial photos
• Black & White - single
panchromatic layer
• Color: 3 layers B-G-R
• Color IR: 3 layers G-RNIR
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Aerial photos
The traditional form of remote
sensing
Pro:
• Can be easily customized to
meet specific requirements
Con:
• Can be expensive
• Need access to plane
• Time consuming interpretation
• Repeat coverage often
infrequent
• Different sun angles
Center for Remote Sensing and Spatial Analysis, Rutgers University
Space-borne Remote Sensing
Emerging Technology
Pro:
•GIS ready
•faster turn around
•acquisition time of 5 minutes gives
equal solar illumination, shadows,
no clouds
•easy to repeat for change detection
Con:
•Significant investment in computer
hardware/software
•Less flexibility in acquisition
Center for Remote Sensing and Spatial Analysis, Rutgers University
Passive electro-optical systems
• Electronic sensors can acquire data
outside the visible spectrum
• Elements sensitive to electro magnetic
energy (EME) of certain wavelengths
focus energy onto a sensor plane. A
prism is used to divide the energy into
specific wavelengths. The CCD’s are
stimulated and produce an electrical
signal equal to the energy focused upon
it. These data are recorded.
• Data are processed and displayed on
computers-images are composed of
“pixels”, whose brightness relates to the
strength of the radiation received from
an area on the surface.
• Digital processing of the data produces
useful information
Center for Remote Sensing and Spatial Analysis, Rutgers University
Design of A Remote Sensing Effort
• Clear definition of the problem
• Evaluation of the potential of remote sensing
techniques
• Identification of appropriate remote sensing data
acquisition procedures
• Determination of the data interpretation
procedures
• Identification of the criteria by which the quality of
information can be evaluated
Center for Remote Sensing and Spatial Analysis, Rutgers University
Resolution
• Four kinds of resolution determined by user needs:
• Spatial Resolution: How small an object do you need
to see (pixel size) and how large an area do you need to
cover (swath width)
• Spectral Resolution: What part of the spectrum do you
want to measure
• Radiometric Resolution: How finely do you need to
quantify the data
• Temporal Resolution: How often do you need to look
Center for Remote Sensing and Spatial Analysis, Rutgers University
Spatial resolution
Instantaneous Field of View (IFOV)
determines the dimension, D,
of the Ground Resolution Cell
(GRC) imaged on the ground
IFOV
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Spatial
resolution
keeps
getting
better...
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Spatial resolution
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1, 3, and 10 meters
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ultra-high spatial resolution
• 24 inch (60 cm)
• 6 inches (15 cm)
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Swath width
Landsat-185km (100 mi)
• 80 m = 40 Mb-4 bands
(MSS)
• 30 m = 320 Mb-6 bands
(TM)
• 10 m = 342.25 Mb-1band
• 5 m = 1.369 Gb -1 band
• 1 m = 34.225 Tb - 1 band
How small do we need?
How much data can we
store and process?
185 by 185 km
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Spectral Resolution: slicing up the
electromagnetic spectrum
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The electromagnetic spectrum
Comparative Sizes: from subatomic to human scales
Atom
Nucleus
Molecule
Human &
larger
Pinhead
Atom
Bacteria
From NY Times graphic 4/8/2003
Center for Remote Sensing and Spatial Analysis, Rutgers University
Honeybee
Spectral wavebands of Landsat TM
Center for Remote Sensing and Spatial Analysis, Rutgers University
Landsat TM-7 bands-8 bit data
Spectral
Landsat TM BAND
(where we look)
1
2
3
4
5 7
Radiometric
(how finely can we
measure the return)
0-63, 0-255, 0-1023
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6
Landsat TM: each waveband provides different information
about earth surface features
Center for Remote Sensing and Spatial Analysis, Rutgers University
Radiometric resolution
•Sensitivity of the detector to differences in EMR signal
strength determines the smallest difference in brightness
value that can be distinguished
Bright
Dark
Determined by the A-to-D quantization
6 bit = 0-63,
8 bit = 0-255,
10 bit = 0-1023
Center for Remote Sensing and Spatial Analysis, Rutgers University
Radiometric resolution
• Higher radiometric
resolution is especially
important for quantitative
applications such as seasurface temperature mapping
where the user wants to
distinguish small differences
in temperature
Center for Remote Sensing and Spatial Analysis, Rutgers University
Satellite remote sensing orbits give repeat coverage
• Geostationary
• Constant view of hemisphere
Polar Sun-synchronous
Covers entire Earth
700-900 km
35,800 km
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SPOT has steerable mirror to increase overpass frequency
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Change Detection
• The ability to
monitor change is
one of the
benefits of remote
sensing
• We can monitor
human and
natural changes
in the landscape
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Hurricane Andrew takes on Florida
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Spatial and temporal resolution
Ground Surveys
50 years
As spatial
resolution
increases, the
revisit
time is also
increased, as
are the
applications
that are
appropriate
and the cost
Aerial Photography
5 years
3 years
28 days
R
e
p
e
a
t
Space photography
SPOT
Landsat-TM
17 days
12 hours
t
i
m
e
NOAA AVHRR
Meteosats
30 min.
.1 m
1m
5m
10-20m 30m
Ground resolution
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1 km
5 km
Many different systems. Which to choose?
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Different sensors and resolutions
sensor
spatial
spectral
radiometric temporal
---------------------------------------------------------------------------------------------------------------AVHRR
Landsat MSS
1.1 and 4 KM
2400 Km
80 meters
185 Km
Landsat TM
30 meters
185 Km
SPOT
10m P / 20m X
60 Km
IRS1
5.8 meters
70 km
IKONOS
1 meter
11 km
4 or 5 bands
10 bit
12 hours
.58-.68, .725-1.1, 3.55-3.93 (0-1023) (1 day, 1 night)
10.3-11.3, 11.5-12.5 (micrometers)
4 bands
6 bit
16 days
.5-.6, .6-.7, .7-.8, .8-1.1
(0-63)
7 bands
8 bit
.45-.52, .52-.6, .63-.69,
(0-255)
.76-.9, 1.55-1.75,
10.4-12.5, 2.08-2.3 um
P -1 band X- 3 bands
8 bit
P - .51-.73 um (0-255)
X - .5-.59, .61-.68, .79-.89 um
1 band
6 bit
.5-.75
(0-63)
1 band
.45-.9
Center for Remote Sensing and Spatial Analysis, Rutgers University
8 bit
(0-255)
14 days
26 days
(2 out of 5)
22 days
3 days
(1.5 out of 3)
Remote Sensing - Summary
• Remote sensing : acquiring and analyzing data using distant devices
recording electromagnetic energy
• Digital scanning devices or analog photography
• Airborne, terrestrial, marine, or orbiting platforms
• Can be passive, sensing existing radiation, or active, sensing radiation
bounced off the surface, as with radar.
• Remote sensing usually involves digital data, but also photography
Usually means both the capture and computerized image analysis of
data. Quantitative, easily incorporated into GIS
• Design of a remote sensing effort must clearly define information needs
and consider the 4 types of remote sensing resolution: radiometric,
spatial, spectral, temporal when considering the types of imagery to use
Center for Remote Sensing and Spatial Analysis, Rutgers University