Remote Sensing. Vandaag. Voordelen Remote Sensing Wat is Remote Sensing? Vier elementen Remote Sensing systeem

Transcription

1 Remote Sensing 1 Vandaag Voordelen Remote Sensing Wat is Remote Sensing? Vier elementen Remote Sensing systeem 2

2 Nederland Vanaf 700 km hoogte Landsat TM mozaïek 3 Europa vanaf km hoogte 4

3 5 Mount Belinda, Sandwich Islands, 60º zuiderbreedte , Aster image 6

4 Provincie Utrecht 1961 Coronabeeld 7 Las Vegas Landsat MSS 13 August 1972 Landsat TM 7 August

5 Voordelen Remote Sensing Overzicht groot gebied Toegang tot ontoegankelijke/verre gebieden Snelle informatiebeschikbaarheid Terugkijken in de tijd 9 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 Monitoring the dynamics of features 10

6 Foto Interpretatie Menselijk oog 7 criteria Context Patroon Schaduw Vorm kleur Grootte Textuur Toon 12 Nu, op dit moment, gebruik je Remote Sensing 13

7 Why all the trouble of including other wavelengths? 14 Non-visible wavelengths reveal other types of information 15

8 Colour infrared film: Adjust the given dye colour of film to other spectral ranges Reflected Light True Colour Film Colour Infrared Film (CIR) Blue Blue - Green Green Blue Red Red Green Infrared - Red 16 Playing with colours using image processing software Ede Veenendaal R,G,B = 4,5,3 Landsat TM Gelderse vallei 17

9 Playing with colours using image processing software Veenendaal R,G,B = 2,4,7 Landsat TM Gelderse vallei 18 Colour assignment to images R = 1 G = 2 B = 3 True Colour 19

10 Colour assignment to images R = 3 G = 2 B = 1 False Colour 20 The Spectrum behaviour <- particle wave -> 21

11 The Electromagnetic Spectrum (EMS) Wavelength < 100 nm nm Frequency > 3x10 15 Hz x10 4 Hz Application Solarium (UV), X-ray photos Visible light c = νλ c : velocity of light, 3x10 8 m/sec ν : frequency (Hz) λ : wavelength (nm, µm) 800 nm - 10 µm 4x x10 13 Hz Infrared scanners 10 µm mm 1 THz Thermal scanners 1 mm - 3 cm 300 GHz - 10 GHz Radar, satellite TV ~ 10 cm 3 GHz Microwave ~ 30 cm 1 GHz Cell phones ~1 m 300 MHz Television m 30 MHz - 3 Mhz Radio, short-wave 300 m 1 MHz Radio, mid-wave 1-10 km 300 KHz - 30 KHz Radio, long-wave > 3000 km < 100 Hz Submarine communication 22 Decompose the wavelengths using a Prism 23

12 Spectral resolution 24 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 μm nm Green μm nm Red μm nm 3 primary together: white light Varying intensity: range of grey tones 25

13 Colour production Addition of wavelengths/colours (TV, monitor) Subtraction of wavelengths/colours using filters Addition Subtraction 26 Four components of a remote sensing system in earth sciences: 1. Source of electromagnetic energy 2. The Sensor 3. The atmosphere 4. The object 27

14 Theory about energy sources: Blackbody: All objects at temperature above 0 K (-273 o C ) emit electromagnetic radiation. So, sun, earth, planets. Energy emitted by an object given by Stefan Boltzman law: M = σ T 4 M: total energy emitted in W m -2 σ: Stefan-Boltzman constant * 10 8 Wm -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) 28 Stefan-Boltzman & Wien models summarized: 29

15 The Atmosphere Processes in the atmosphere absorption & scattering Space shuttle view of the atmosphere 30 Observation through the atmosphere: Absorption Scattering 31

16 Selective Rayleigh scattering Day time B G R Sun Atmosphere Blue sky Earth Atmosphere Earth Green Red Blue Sunset Sun Waarom zijn schaduwen donkerder op de maan? 32 Atmosferische Transmissie Remote Sensing waarnemingen zijn beperkt tot atmosferische vensters 33

17 Spectrale positie Landsat TM banden & atmospherische transmissie 34 Beeldverwerking: haze correctie 35

18 Objecten Leaf Pigments Cell Structure Water content Dominant factor controlling leaf reflectance Reflectance Green peak Wavelength (nm) Green 36 De-colouring of leaves and their spectra: Photo synthetically Active, Senescing Yellow & Red, Senescent/dead 37

19 Specular versus diffuse reflectance 38 Specular versus diffuse reflectance 39

20 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 40 Active and Passive Remote Sensing Systems 41

21 Dynamic range of the sensor system (quantization): the range of incoming radiance that the sensor can handle bits GL s range (b-w) The Sensors: Land observation satellites: Landsat MSS & Thematic Mapper (TM) SPOT XS & SPOT PAN ASTER IKONOS Meteorological satellites NOAA-AVHRR Meteosat (& GOES) Airborne systems: B&W, CIR photo systems AVIRIS CAESAR EPS-A 43

22 NOAA-AVHRR Landsat TM Ikonos 44