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Remote Sensing
Vandaag
• Voordelen Remote Sensing
• Wat is Remote Sensing?
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Nederland
Vanaf 700 km hoogte
Landsat TM mozaïek
Europa vanaf 36000 km hoogte5
Mount Belinda, Sandwich Islands, 60º zuiderbreedte 23-9-2005, Aster image
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Provincie Utrecht 1961
Coronabeeld
Landsat MSS 13 August 1972 Landsat TM 7 August 2000 Las Vegas
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Voordelen Remote Sensing
• Overzicht groot gebied
• Toegang tot ontoegankelijke/verre gebieden
• Snelle informatiebeschikbaarheid
• Terugkijken in de tijd
Definition of Remote Sensing:
Remote Sensing is the science or the technique of deriving information about objects at the Earth surface from images using (parts of) the electromagnetic spectrum
• Measuring electromagnetic energy (light), reflected or emitted • Non-destructive method, no physical contact
• Surveying the spatial distribution of objects • Determining properties of objects
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Foto Interpretatie
Toon
Context Patroon Schaduw Vorm
Textuur Grootte
Menselijk oog 7 criteria
kleur
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Why all the trouble of including other wavelengths ?
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Reflected Light True Colour Film Colour Infrared Film (CIR)
Blue Blue
-Green Green Blue
Red Red Green
Infrared - Red
Colour infrared film:
Adjust the given dye colour of film to other spectral ranges
Ede Veenendaal
Playing with colours using ‘image processing software’
R,G,B = 4,5,3
Landsat TM Gelderse vallei
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Veenendaal
Playing with colours using ‘image processing software’
R,G,B = 2,4,7
Landsat TM Gelderse vallei
Colour assignment to images
20 1 2 3 False Colour R = 3 G = 2 B = 1
Colour assignment to images
The Spectrum behaviour
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The Electromagnetic Spectrum (EMS)
Submarine communication < 100 Hz > 3000 km Radio, long-wave 300 KHz - 30 KHz 1 - 10 km Radio, mid-wave 1 MHz 300 m Radio, short-wave 30 MHz - 3 Mhz 10 - 100 m Television 300 MHz ~1 m Cell phones 1 GHz ~ 30 cm Microwave 3 GHz ~ 10 cm Radar, satellite TV 300 GHz - 10 GHz 1 mm - 3 cm Thermal scanners 1 THz 10 µm - 0.3 mm Infrared scanners 4x1014- 3x1013Hz 800 nm - 10 µm Visible light 10 15- 4x104Hz 300 - 800 nm
Solarium (UV), X-ray photos > 3x1015Hz < 100 nm Application Frequency Wavelength
c = νλ
c : velocity of light, 3x108 m/sec ν : frequency (Hz) λ : wavelength (nm, µm)24
Spectral resolution
Colours
• Interpretation of RS images often based on colours (analogue/digital) • Human eye sensitive to only 3 colours
other colours are products of mixing • 3 Primary colours:
Blue 0.4 – 0.5 μm 400 – 500 nm Green 0.5 – 0.6 μm 500 – 600 nm Red 0.6 – 0.7 μm 600 – 700 nm • 3 primary together: white light
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Colour production
• Addition of wavelengths/colours (TV, monitor) • Subtraction of wavelengths/colours using filters
Addition Subtraction
Four components of a remote sensing system in earth sciences: 1. Source of electromagnetic energy
2. The Sensor 3. The atmosphere 4. The object
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Theory about energy sources:
Blackbody:
All objects at temperature above 0 K (-273 oC ) emit electromagnetic radiation. So, sun, earth, planets.
Energy emitted by an object given by Stefan Boltzman law:
M = σ T4
M: total energy emitted in W m-2
σ: Stefan-Boltzman constant 5.6697 * 10–8Wm-2 K-4 T: Absolute temperature (K)
Wien’s law gives spectral variation of emitted radiance: λ max = A/T
λ max : wavelength of maximum spectral radiant exitance (μm) A: Wien’s constant 2898 (μm K)
T: temperature (K)
30 The Atmosphere
Processes in the atmosphere absorption & scattering
Space shuttle view of the atmosphere
32 Blue sky Day time Earth Atmosphere B G R Sun Earth Sunset Blue Red Sun Green Atmosphere
Selective Rayleigh scattering
Waarom zijn schaduwen donkerder op de maan?
Atmosferische Transmissie
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Spectrale positie Landsat TM banden & atmospherische transmissie
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Leaf
Pigments Cell
Structure Water content
Dominant factor controlling leaf reflectance Green Wavelength (nm) Reflectance -0.05 0.05 0.15 0.25 0.35 0.45 0.55 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400 Green peak Objecten
De-colouring of leaves and their spectra: Photo synthetically Active,
Senescing Yellow & Red, Senescent/dead
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Specular versus diffuse reflectance
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The Sensor
Wide range of remote sensors available: - Airborne – spaceborne
- Spectral bands (number & spectral position) - Spectral band width
- Spatial resolution (or pixel size) - Wide and narrow Field of View - Orbit: geostationary & polar - Active and passive systems
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Dynamic range of the sensor system (quantization): the range of incoming radiance
that the sensor can handle bits GL’s range (b-w)
1 2 0-1 2 4 0-3 3 8 0-7 4 16 0-15 5 32 0-31 6 64 0-63 7 128 0-127 8 256 0-255 9 512 0-511 10 1024 0-1023 The Sensors:
Land observation satellites:
• Landsat MSS & Thematic Mapper (TM) • SPOT XS & SPOT PAN
• ASTER • IKONOS
Meteorological satellites • NOAA-AVHRR
• Meteosat (& GOES) Airborne systems:
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Ikonos Landsat TM