Weather monitoring and forecasting was one of the first civilian (as opposed to military) applications of satellite remote sensing, dating back to the first true weather satellite, TIROS-1 (Television and Infrared Observation Satellite - 1), launched in

1
Weather monitoring and forecasting was one of the
first civilian (as opposed to military)
applications of satellite remote sensing, dating
back to the first true weather satellite, TIROS-1
(Television and Infrared Observation Satellite -
1), launched in 1960 by the United States.
Several other weather satellites were launched
over the next five years, in near-polar orbits,
providing repetitive coverage of global weather
patterns. In 1966, NASA (the U.S. National
Aeronautics and Space Administration) launched
the geostationary Applications Technology
Satellite (ATS-1) which provided hemispheric
images of the Earth's surface and cloud cover
every half hour.
For the first time, the development and movement
of weather systems could be routinely monitored.
Today, several countries operate weather, or
meteorological satellites to monitor weather
conditions around the globe. Generally speaking,
these satellites use sensors which have fairly
coarse spatial resolution (when compared to
systems for observing land) and provide large
areal coverage. Their temporal resolutions are
generally quite high, providing frequent
observations of the Earth's surface, atmospheric
moisture, and cloud cover, which allows for
near-continuous monitoring of global weather
conditions, and hence - forecasting. Here we
review a few of the representative
satellites/sensors used for meteorological
applications.
2
GOES
The GOES (Geostationary Operational Environmental
Satellite) System is the follow-up to the ATS
series. They were designed by NASA for the
National Oceanic and Atmospheric Administration
(NOAA) to provide the United States National
Weather Service with frequent, small-scale
imaging of the Earth's surface and cloud cover.
The GOES series of satellites have been used
extensively by meteorologists for weather
monitoring and forecasting for over 20 years.
These satellites are part of a global network of
meteorological satellites spaced at approximately
70 longitude intervals around the Earth in order
to provide near-global coverage. Two GOES
satellites, placed in geostationary orbits 36000
km above the equator, each view approximately
one-third of the Earth. One is situated at 75W
longitude and monitors North and South America
and most of the Atlantic Ocean. The other is
situated at 135W longitude and monitors North
America and the Pacific Ocean basin.
3
Together they cover from 20W to 165E longitude.
This GOES image covers a portion of the
southeastern United States, and the adjacent
ocean areas where many severe storms originate
and develop. This image shows Hurricane
approaching the southeastern United States and
the Bahamas in September of 1996.
Two generations of GOES satellites have been
launched, each measuring emitted and reflected
radiation from which atmospheric temperature,
winds, moisture, and cloud cover can be derived.
The first generation of satellites consisted of
GOES-1 (launched 1975) through GOES-7 (launched
1992).
GOES-8 and the other second generation GOES
satellites have separate imaging and sounding
instruments. The imager has five channels sensing
visible and infrared reflected and emitted solar
radiation. The infrared capability allows for day
and night imaging.
4
GOES Bands
GOES Bands
5
NOAA AVHRR
NOAA is also responsible for another series of
satellites which are useful for meteorological,
as well as other, applications. These satellites,
in sun-synchronous, near-polar orbits (830-870 km
above the Earth), are part of the Advanced TIROS
series (originally dating back to 1960) and
provide complementary information to the
geostationary meteorological satellites (such as
GOES). Two satellites, each providing global
coverage, work together to ensure that data for
any region of the Earth is no more than six hours
old. One satellite crosses the equator in the
early morning from north-to-south while the other
crosses in the afternoon.
The primary sensor on board the NOAA satellites,
used for both meteorology and small-scale Earth
observation is the Advanced Very High Resolution
Radiometer (AVHRR). The AVHRR sensor detects
radiation in the visible, near and mid infrared,
and thermal infrared portions of the
electromagnetic spectrum, over a swath width of
3000 km.
6
NOAA AVHRR Bands
7
 Other Weather Satellites
There are several other meteorological satellites
in orbit, launched and operated by other
countries, or groups of countries. These include
Japan, with the GMS satellite series, and the
consortium of European communities, with the
METEOSAT satellites. Both are geostationary
satellites situated above the equator over Japan
and Europe, respectively.
8
TOVS(TIROS-N OPER. VERT. SOUNDER BY NOAA)

• There are 3 observation systems
• IRS (high resolution Infrared radiation sounder)
• MSU (microwave sounding unit)
• SSU (microwave sounding unit)

9
Land Observation Satellites/Sensors
Landsat-1, was launched by NASA in 1972.
Initially referred to as ERTS-1, (Earth Resources
Technology Satellite), Landsat was designed as an
experiment to test the feasibility of collecting
multi-spectral Earth observation data
All Landsat satellites are placed in near-polar,
sun-synchronous orbits. The first three
satellites (Landsats 1-3) are at altitudes around
900 km and have revisit periods of 18 days while
the later satellites are at around 700 km and
have revisit periods of 16 days.
10
A number of sensors have been on board the
Landsat series of satellites, including the
Return Beam Vidicon (RBV) camera systems, the
MultiSpectral Scanner (MSS) systems, and the
Thematic Mapper (TM). The most popular instrument
in the early days of Landsat was the
MultiSpectral Scanner (MSS) and later the
Thematic Mapper (TM). Each of these sensors
collected data over a swath width of 185 km, with
a full scene being defined as 185 km x 185 km.
MSS Bands
11
TM Bands
12
(Système Pour l'Observation de la Terre) is a
series of Earth observation imaging satellites
designed and launched by CNES (Centre National
d'Études Spatiales) of France, with support from
Sweden and Belgium.
SPOT
The Indian Remote Sensing (IRS) satellite series,
combines features from both the Landsat MSS/TM
sensors and the SPOT HRV sensor.
IRS
The first is the MEIS-II (Multispectral
Electro-optical Imaging Scanner) sensor developed
for the Canada Centre for Remote Sensing.
The Compact Airborne Spectrographic Imager, is a
leader in airborne imaging, being the first
commercial imaging spectrometer.
CASI
13
Marine Observation Satellites/Sensors
The Nimbus-7 satellite, launched in 1978, carried
the first sensor, the Coastal Zone Colour Scanner
(CZCS), specifically intended for monitoring the
Earth's oceans and water bodies.
The primary objective of this sensor was to
observe ocean colour and temperature,
particularly in coastal zones, with sufficient
spatial and spectral resolution to detect
pollutants in the upper levels of the ocean and
to determine the nature of materials suspended in
the water column.
The first Marine Observation Satellite (MOS-1)
was launched by Japan in February, 1987 and was
followed by its successor, MOS-1b, in February of
1990. These satellites carry three different
sensors a four-channel Multispectral Electronic
Self-Scanning Radiometer (MESSR), a four-channel
Visible and Thermal Infrared Radiometer (VTIR),
and a two-channel Microwave Scanning Radiometer
(MSR), in the microwave portion of the spectrum.
MOS
14
They are used for very specific detection and
monitoring of various ocean phenomena including
ocean primary production and phytoplankton
processes, ocean influences on climate processes
(heat storage and aerosol formation), and
monitoring of the cycles of carbon, sulfur, and
nitrogen.
SeaWiFS
(Sea-viewing Wide-Field-of View Sensor)
FLIR
Typically positioned on aircraft or helicopters,
and imaging the area ahead of the platform, FLIR
systems provide relatively high spatial
resolution imaging that can be used for military
applications, search and rescue operations, law
enforcement, and forest fire monitoring.
Forward Looking InfraRed systems
An active imaging technology very similar to
RADAR. Lidar is also used in atmospheric studies
to examine the particle content of various layers
of the Earths atmosphere and acquire air density
readings and monitor air currents.
Lidar
LIght Detection And Ranging
15
RADAR systems are active sensors which provide
their own source of electromagnetic energy.
RADAR
Because RADAR provides its own energy source,
images can be acquired day or night.
RAdio Detection And Ranging
Also, microwave energy is able to penetrate
through clouds and most rain, making it an
all-weather sensor.
16
Data Reception, Transmission, and Processing
There are three main options for transmitting
data acquired by satellites to the surface. The
data can be directly transmitted to Earth if a
Ground Receiving Station (GRS) is in the line of
sight of the satellite
(A). the data can be recorded on board the
satellite directly
(B) for transmission to a GRS at a later time.
Data can also be relayed to the GRS through the
Tracking and Data Relay Satellite System (TDRSS)
(C), which consists of a series of communications
satellites in geosynchronous orbit. The data are
transmitted from one satellite to another until
they reach the appropriate GRS.
17
For many sensors it is possible to provide
customers with quick-turnaround imagery when they
need data as quickly as possible after it is
collected. Near real-time processing systems
are used to produce low resolution imagery in
hard copy or soft copy (digital) format within
hours of data acquisition. Such imagery can
then be faxed or transmitted digitally to end
users.
18
Microwave sensing encompasses both active and
passive forms of remote sensing
the microwave portion of the spectrum covers the
range from approximately 1cm to 1m in wavelength
Longer wavelength microwave radiation can
penetrate through cloud cover, haze, dust, and
all but the heaviest rainfall
19
A passive microwave sensor detects the naturally
emitted microwave energy within its field of
view.
This emitted energy is related to the temperature
and moisture properties of the emitting object or
surface.
Passive microwave sensors are typically
radiometers or scanners
The microwave energy recorded by a passive sensor
can be emitted by the atmosphere (1), reflected
from the surface (2), emitted from the surface
(3), or transmitted from the subsurface (4).
20
meteorologists can use passive microwaves to
measure atmospheric profiles and to determine
water and ozone content in the atmosphere
Applications of passive microwave remote sensing
include meteorology, hydrology, and oceanography.
Oceanographic applications include mapping sea
ice, currents, and surface winds as well as
detection of pollutants
Hydrologists use passive microwaves to measure
soil moisture since microwave emission is
influenced by moisture content.
21
Active microwave sensors provide their own source
of microwave radiation to illuminate the target.
Active microwave sensors are generally divided
into two distinct categories imaging and
non-imaging.
The most common form of imaging active microwave
sensors is RADAR.
The radars sensor transmits a microwave (radio)
signal towards the target and detects the
backscattered portion of the signal.
22
The strength of the backscattered signal is
measured to discriminate between different
targets and the time delay between the
transmitted and reflected signals determines the
distance (or range) to the target.
Non-imaging microwave sensors include altimeters
and scatterometers.
Radar altimeters transmit short microwave pulses
and measure the round trip time delay to targets
to determine their distance from the sensor.
Scatterometers are also generally non-imaging
sensors and are used to make precise quantitative
measurements of the amount of energy
backscattered from targets.
23
Scatterometry measurements over ocean surfaces
can be used to estimate wind speeds based on the
sea surface roughness.
Ground-based scatterometers are used extensively
to accurately measure the backscatter from
various targets in order to characterize
different materials and surface types. This is
analogous to the concept of spectral reflectance
curves in the optical spectrum.
24
As with passive microwave sensing, a major
advantage of radar is the capability of the
radiation to penetrate through cloud cover and
most weather conditions.
Because radar is an active sensor, it can also be
used to image the surface at any time, day or
night.
These are the two primary advantages of radar
all-weather and day or night imaging.
25
Radar Basics
a radar is essentially a ranging or distance
measuring device
It consists fundamentally of a transmitter, a
receiver, an antenna, and an electronics system
to process and record the data.
The transmitter generates successive short bursts
(or pulses of microwave (A) at regular intervals
which are focused by the antenna into a beam (B).
The antenna receives a portion of the
transmitted energy reflected (or backscattered)
from various objects within the illuminated beam
(C)
26
(No Transcript)
27
the polarization of the radiation is also
important. Polarization refers to the orientation
of the electric field
Most radars are designed to transmit microwave
radiation either horizontally polarized (H) or
vertically polarized (V).
HH - for horizontal transmit and horizontal
receive, VV - for vertical transmit and vertical
receive, HV - for horizontal transmit and
vertical receive, and VH - for vertical transmit
and horizontal receive.
28
Airborne and Spaceborne Radar Systems
Convair-580 C/X SAR system
AirSAR system
JERS-1
Sea Ice and Terrain Assessment (STAR)
ERS-1
SEASAT
29
Targets may be a point, line, or area feature.
This means that they can have any form, from a
bus in a parking lot or plane on a runway, to a
bridge or roadway, to a large expanse of water or
a field.
In order to take advantage of and make good use
of remote sensing data, we must be able to
extract meaningful information from the imagery.
This brings us to the topic of discussion in this
chapter - interpretation and analysis
Interpretation and analysis of remote sensing
imagery involves the identification and/or
measurement of various targets in an image in
order to extract useful information about them.
Targets in remote sensing images may be any
feature or object which can be observed in an
image, and have the following characteristics
30
Targets may be a point, line, or area feature.
This means that they can have any form, from a
bus in a parking lot or plane on a runway, to a
bridge or roadway, to a large expanse of water or
a field.
The target must be distinguishable it must
contrast with other features around it in the
image.
31
Much interpretation and identification of targets
in remote sensing imagery is performed manually
or visually, i.e. by a human interpreter.
In many cases this is done using imagery
displayed in a pictorial or photograph-type
format, independent of what type of sensor was
used to collect the data and how the data were
collected.
In this case we refer to the data as being in
analog format.
remote sensing images can also be represented in
a computer as arrays of pixels, with each pixel
corresponding to a digital number, representing
the brightness level of that pixel in the image
32
In this case, the data are in a digital format.
Visual interpretation may also be performed by
examining digital imagery displayed on a computer
screen. Both analogue and digital imagery can be
displayed as black and white (also called
monochrome) images, or as colour images by
combining different channels or bands
representing different wavelengths.
When remote sensing data are available in digital
format, digital processing and analysis may be
performed using a computer. Digital processing
may be used to enhance data as a prelude to
visual interpretation. Digital processing and
analysis may also be carried out to automatically
identify targets and extract information
completely without manual intervention by a human
interpreter. However, rarely is digital
processing and analysis carried out as a complete
replacement for manual interpretation. Often, it
is done to supplement and assist the human
analyst.
33
Manual interpretation and analysis dates back to
the early beginnings of remote sensing for air
photo interpretation. Digital processing and
analysis is more recent with the advent of
digital recording of remote sensing data and the
development of computers. Both manual and digital
techniques for interpretation of remote sensing
data have their respective advantages and
disadvantages. Generally, manual interpretation
requires little, if any, specialized equipment,
while digital analysis requires specialized, and
often expensive, equipment. Manual interpretation
is often limited to analyzing only a single
channel of data or a single image at a time due
to the difficulty in performing visual
interpretation with multiple images.
The computer environment is more amenable to
handling complex images of several or many
channels or from several dates. In this sense,
digital analysis is useful for simultaneous
analysis of many spectral bands and can process
large data sets much faster than a human
interpreter.
34
Manual interpretation is a subjective process,
meaning that the results will vary with different
interpreters. Digital analysis is based on the
manipulation of digital numbers in a computer and
is thus more objective, generally resulting in
more consistent results. However, determining the
validity and accuracy of the results from digital
processing can be difficult.
It is important to reiterate that visual and
digital analyses of remote sensing imagery are
not mutually exclusive. Both methods have their
merits. In most cases, a mix of both methods is
usually employed when analyzing imagery. In fact,
the ultimate decision of the utility and
relevance of the information extracted at the end
of the analysis process, still must be made by
humans.
35
Recognizing targets is the key to interpretation
and information extraction. Observing the
differences between targets and their backgrounds
involves comparing different targets based on
any, or all, of the visual elements of tone,
shape, size, pattern, texture, shadow, and
association.
Tone refers to the relative brightness or colour
of objects in an image. Generally, tone is the
fundamental element for distinguishing between
different targets or features. Variations in tone
also allows the elements of shape, texture, and
pattern of objects to be distinguished.
36
Shape refers to the general form, structure, or
outline of individual objects. Shape can be a
very distinctive clue for interpretation.
Straight edge shapes typically represent urban or
agricultural (field) targets, while natural
features, such as forest edges, are generally
more irregular in shape, except where man has
created a road or clear cuts. Farm or crop land
irrigated by rotating sprinkler systems would
appear as circular shapes.
37
Size of objects in an image is a function of
scale. It is important to assess the size of a
target relative to other objects in a scene, as
well as the absolute size, to aid in the
interpretation of that target. A quick
approximation of target size can direct
interpretation to an appropriate result more
quickly. For example, if an interpreter had to
distinguish zones of land use, and had identified
an area with a number of buildings in it, large
buildings such as factories or warehouses would
suggest commercial property, whereas small
buildings would indicate residential use.
38
Pattern refers to the spatial arrangement of
visibly discernible objects. Typically an orderly
repetition of similar tones and textures will
produce a distinctive and ultimately recognizable
pattern. Orchards with evenly spaced trees, and
urban streets with regularly spaced houses are
good examples of pattern.
39
Texture refers to the arrangement and frequency
of tonal variation in particular areas of an
image. Rough textures would consist of a mottled
tone where the grey levels change abruptly in a
small area, whereas smooth textures would have
very little tonal variation. Smooth textures are
most often the result of uniform, even surfaces,
such as fields, asphalt, or grasslands. A target
with a rough surface and irregular structure,
such as a forest canopy, results in a rough
textured appearance. Texture is one of the most
important elements for distinguishing features in
radar imagery.
40
Shadow is also helpful in interpretation as it
may provide an idea of the profile and relative
height of a target or targets which may make
identification easier. However, shadows can also
reduce or eliminate interpretation in their area
of influence, since targets within shadows are
much less (or not at all) discernible from their
surroundings. Shadow is also useful for enhancing
or identifying topography and landforms,
particularly in radar imagery.
41
Association takes into account the relationship
between other recognizable objects or features in
proximity to the target of interest. The
identification of features that one would expect
to associate with other features may provide
information to facilitate identification. In the
example, commercial properties may be associated
with proximity to major transportation routes,
whereas residential areas would be associated
with schools, playgrounds, and sports fields. In
our example, a lake is associated with boats, a
marina, and adjacent recreational land.
42
Digital Image Processing
In today's world of advanced technology where
most remote sensing data are recorded in digital
format, virtually all image interpretation and
analysis involves some element of digital
processing. Digital image processing may involve
numerous procedures including formatting and
correcting of the data, digital enhancement to
facilitate better visual interpretation, or even
automated classification of targets and features
entirely by computer. In order to process remote
sensing imagery digitally, the data must be
recorded and available in a digital form suitable
for storage on a computer tape or disk.
Obviously, the other requirement for digital
image processing is a computer system, sometimes
referred to as an image analysis system, with the
appropriate hardware and software to process the
data. Several commercially available software
systems have been developed specifically for
remote sensing image processing and analysis.
43
For discussion purposes, most of the common image
processing functions available in image analysis
systems can be categorized into the following
four categories
Preprocessing Image Enhancement Image
Transformation Image Classification and Analysis

Preprocessing functions involve those operations
that are normally required prior to the main data
analysis and extraction of information, and are
generally grouped as radiometric or geometric
corrections.
44
Radiometric corrections include correcting the
data for sensor irregularities and unwanted
sensor or atmospheric noise, and converting the
data so they accurately represent the reflected
or emitted radiation measured by the sensor.
Geometric corrections include correcting for
geometric distortions due to sensor-Earth
geometry variations, and conversion of the data
to real world coordinates (e.g. latitude and
longitude) on the Earth's surface.
45
The objective of the second group of image
processing functions grouped under the term of
image enhancement, is solely to improve the
appearance of the imagery to assist in visual
interpretation and analysis. Examples of
enhancement functions include contrast stretching
to increase the tonal distinction between various
features in a scene, and spatial filtering to
enhance (or suppress) specific spatial patterns
in an image.
46
Image transformations are operations similar in
concept to those for image enhancement. However,
unlike image enhancement operations which are
normally applied only to a single channel of data
at a time, image transformations usually involve
combined processing of data from multiple
spectral bands. Arithmetic operations (i.e.
subtraction, addition, multiplication, division)
are performed to combine and transform the
original bands into "new" images which better
display or highlight certain features in the
scene. We will look at some of these operations
including various methods of spectral or band
ratioing, and a procedure called principal
components analysis which is used to more
efficiently represent the information in
multichannel imagery.
47
Image classification and analysis operations are
used to digitally identify and classify pixels in
the data. Classification is usually performed on
multi-channel data sets (A) and this process
assigns each pixel in an image to a particular
class or theme (B) based on statistical
characteristics of the pixel brightness values.
There are a variety of approaches taken to
perform digital classification. We will briefly
describe the two generic approaches which are
used most often, namely supervised and
unsupervised classification.
48

• Some project titles
• Pre-processing in image analysis of satellite
  pictures
• Image Enhancement and Image Transformations in
  remote sensing
• Image Classification, Data Integration and
  Analysis
• Multispectral Scanning and Thermal Imaging of
  satellites
• Radiometric, spectral and temporal resolutions in
  remote sensing
• Remote sensing applications for Agriculture
• Remote sensing applications for Hydrology
• Remote sensing applications for Geology
• Remote sensing applications for Oceans and
  Coastal