Remote Sensing

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Remote Sensing

• An Introduction

Lecture 1
2
Remote Sensing

• Definition the acquisition of (environmental)
  data without contact with the object or surface
• Sensors mounted on airborne and satellite
  platforms
• Major environmental data source
• Airborne platforms can include kites, balloons,
  model aircraft, microlights, autogyros, light
  aircraft, and helicopters etc..

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Remote Sensing

• Airborne Sensors are either
• Cameras (including traditional and digital camera
  and video)
• Scanners
• Traditional versus Digital

4
Remote Sensing

• Electromagnetic Spectrum (EMS)
• Visible, Near Infrared (NIR), Thermal Infrared
  (TIR), Microwave wavelengths
• Short Wave (SW) to Long Wave (LW)

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Remote Sensing
6
Remote Sensing
Sun-Sensor-Terrain System

• Energy from the Sun (primary source)
• Interacts with surface (land, water, vegetation)
• Absorbed (A), Reflected (R), Transmitted (T), or
  Emitted (E)
• Reflected and Emitted energy from surface
  detected and recorded by remote sensor
• Contains information about the surface
• Image-based remote sensing
• Passive Remote Sensing (Reflected and Emitted)
• Also Active Remote Sensing
• Weak microwave signals mean that some specialised
  remote sensing devices have to be constructed
  that provide their own energy source
• Microwave energy is generated by the device and
  bounced back off the surface and recorded by the
  device
• Basis of RADAR RAdio Detection And Ranging

Atmosphere
E
R
A
T
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Remote Sensing

• Fundamental Concept of Resolution in remote
  sensing
• Spatial (detail)
• Spectral (wavelengths)
• Temporal (time)
• Radiometric

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Remote Sensing
Spectral Bands (in micrometers) Landsat TM
(Thematic Mapper) 1. 0.45 - 0.52 (Blue) 2.
0.52 - 0.60 (Green) 3. 0.63 - 0.69 (Red) 4.
0.76 - 0.90 (Near-Ifrared) 5. 1.55 - 1.75
(Middle-Infrared) 6. 10.4 - 12.5 (Thermal) 7.
2.08 - 2.35 (Middle-Infrared)
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Remote Sensing

• Spatial Resolution (Size of IFOV) Landsat TM
  (Thematic Mapper)
• Bands 1,2,3,4,57 30 m Band 6 120 m

1 2 5 10 20 30

• Temporal Resolution Landsat 1,2, and 3 (Both TM
  and MSS)
• 18 Days (Every 251 Orbits) (frequency of revisit)

• Radiometric Resolution Landsats 1, 2 3
  Multispectral Scanner 6-Bit (64 levels)
• Landsats 4 5 Thematic Mapper and Multispectral
  Scanner 8-Bit (256 levels)

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Remote Sensing

• Aerial photographs are the cheapest and most
  familiar examples of RS
• Paper prints but now digital, computer
  compatible
• Aerial photographs provide the highest spatial
  resolution (smallest object that can be detected
  or resolved)
• But poorest spectral resolution
• Usually vertical
• Mono, Stereo, or Orthophotographs
• Panchromatic, Colour, Colour Infrared (CIR),
  Multispectral

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Remote Sensing

• More recently other airborne sensors
• Combine high spatial resolution and multispectral
  capability, extend spectral resolution
• CASI Compact Airborne Spectrographic Imager
• ATM Airborne Thematic Mapper
• LIDAR
• Thermal Infrared (TIR)
• RADAR

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Remote Sensing
Oil Plume
CASI
Sewage Discharge
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Remote Sensing
CASI
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Remote Sensing
ATM Sediment Dynamics Intertidal Surfaces
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Remote Sensing
LIDAR
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Remote Sensing
LIDAR DEM
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Remote Sensing
TIR
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Remote Sensing

• Satellite remote sensing dates back to 1972 with
  launch of first Landsat series in the USA
• Subsequently many satellites and sensors such as
  Landsat, SPOT, RADARSAT, ERS, ENVISAT etc.
• Many land-based, some coastal and marine e.g.
  CZCS and Seasat

Landsat TM
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Remote Sensing
SPOT
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Remote Sensing
SST - AVHRR
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Remote Sensing
AVHRR - Algal Blooms
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Remote Sensing
ERS-1 RADAR Oil Spills
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Remote Sensing
Aqua MODIS "true color" image from 21 March 2001
showing the Mississippi and Atchafalaya River
sediment plumes entering the Gulf of Mexico.
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Remote Sensing
QuickBird - MS - Coast of Spain
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Remote Sensing
ENVISAT MS image - Coast of Africa - Namibia -
Namib Desert
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Remote Sensing
IKONOS - Colour and Panchromatic - San Francisco
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Remote Sensing
SIDE SCAN SONAR
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Remote Sensing

• Over time improved spatial, spectral and temporal
  resolution
• Large volumes of digital data/imagery
• Available from multiple sources
• On Tape and now CD
• Expensive to purchase 25.00 - N,000!

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Remote Sensing

• Analog imagery is usually analysed and
  interpreted using photointerpretation and factors
  (e.g. tone, texture, size, shape, association,
  colour..)
• Digital data and imagery can be interpreted in a
  traditional way - on screen
• Processed using tools and techniques of Digital
  Image Processing (DIP)

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Remote Sensing
large area coverage
small

• Different sources of remote sensing data and
  imagery are complementary
• Provide different information
• Many different applications as you will see!

pattern distribution
Scale
detail
small area coverage
large