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Spectral Signatures Passive Sensors (receive reflected or emitted signals from the surface, including optical, thermal and microwave sensors ) Active Sensors.

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Presentation on theme: "Spectral Signatures Passive Sensors (receive reflected or emitted signals from the surface, including optical, thermal and microwave sensors ) Active Sensors."— Presentation transcript:

1 Spectral Signatures Passive Sensors (receive reflected or emitted signals from the surface, including optical, thermal and microwave sensors ) Active Sensors (generate and emit radiation to the surface and receive the returned signals, Including RADAR, Laser, etc.)

2 Reflectance (reflectivity) Ratio of total reflected radiation divided by the total incoming radiation Spectral Reflectance Reflectance for a given range of wavelength Bi-Directional Reflectance Albedo Reflectance for a fixed view-target-sun geometry Reflectance for total incoming radiation in all direction for wavelength ranging from 0.3 to 4.0  m

3 128 Radiance and Reflectance of a Pixel 19251 RedNear-InfraredMid-Infrared Each band has its own sensor calibration (gain and offset) which must be considered in the image interpretation 128:1 192:2 51:3

4 From DN to Radiance to Reflectance 1 G=(-3.58E-05)*D+1.376 0.4863 1959.2 2 G=(-2.10E-05)*D+0.737 0.5706 1827.4 3 G=(-1.04E-05)*D+0.932 0.6607 1550.0 4 G=(-3.20E-06)*D+1.075 0.8382 1040.8 5 G=(-2.64E-05)*D+7.329 1.677 220.75 7 G=(-3.81E-04)*D+16.02 2.223 74.960 Source: CCRS Web site LANDSAT TM Spectral Band Calibration Gain Coefficient (counts/(W/m 2 /sr/  m)) Characteristic Wavelength (  m) Solar Irradiance (W/m 2 /  m) Radiance = (DN - Offset)/Gain Reflectance =   Radiance/Solar Irradiance D = days since launch

5 If the input signal exceeds the amount for which the sensor was designed, the system response will become non-linear or reach the saturation level. This is a common occurrence in land remote sensing systems when they image bright clouds and/or snow cover, for example. Linear Region y = a.x + b (DN = gain*Radiance + offset) Non-Linear Region Saturation Offset b Input Value x (radiance) Source: CCRS Web site y (DN)

6 Spectral Reflectance of Vegetation in the visible Visible BLUE GREENRED REFLECTANCE Low High 16.4

7 Time variation of Vegetation Spectral Reflectance BLUE GREEN RED REFLECTANCE Low High Fall Summe r Sugar Maple Aspen 16.4

8 Vegetation Spectral Reflectance BLUEGREEN RED REFLECTANCE Low High NORMAL LEAF LEAF INFILTRATED WITH WATER NEAR-INFRARED 16.4

9 SWIR Spectral Response to Wetness of Feather Moss And the Utility of Shortwave Infrared (SWIR) dry wet

10

11 Spectral Reflectivity of Vegetation Black Spruce Needle Moss BLUE GREENRED 16.4

12 Vegetation Spectral Reflectance BLUEGREEN RED REFLECTANCE Low High WHITE LEAF NEAR-INFRARED GREEN LEAF 16.4

13 Summery for plant leaves Visible reflectance controlled by pigments B G R Near Infrared reflectance controlled by cell structure Mid Infrared reflectance controlled by water content Reflectance 720 1300 2500 nm380

14 Other factors affecting the spectral signature of vegetation Age (0.7  m) diseases (e.g. yellow discoloration 0.55-0.75  m) 16.4 17.4

15 Spectral signature for plant canopies A plant canopy is the whole layer of vegetation of considerable horizontal extent (In case of forests, it is not just a tree crown, but consists of many tree crowns ) Canopy

16 Vegetation Spectral Reflectivity BLUEGREEN RED REFLECTANCE Low High ASPEN NEAR-INFRARED SPRUCE 16.4

17 Vegetation Spectral Reflectivity BLUEGREEN RED REFLECTANCE (%) BROADLEAF FORESTS NEAR-INFRARED CONIFEROUS FORESTS GRASS 0 20 40 60 80 100 16.4

18 Water Spectral Reflectance 18.2 BLUE GREEN REDNEAR-INFRARED Clear Water Moderate Turbidity High Turbidity REFLECTANCE Low High

19 VISIBLENEAR-IRMID-INFRARED REFLECTANCE Low High Clouds Snow Spectral Reflectance of Clouds versus Snow

20 Soil Spectral Reflectivity VISIBLENEAR-IRMID-INFRARED REFLECTANCE Low High Dry Soil Moist Soil

21 LANDSAT TM SPOT-HRV SPOT- PAN JERS-OPS AVHRR Atmospheric Absorption Bands Vegetation Sandstone Limestone Shale Reflected IR Wavelength 0.50 1.00 1.50 2.00 2.50 Blue Green Red Wavelength (  m) 17.5 1 2 3 4 5 7 1 2 3 1 2 3,4 5 7 8 9 1 2

22 Spectral Reflectivity of Minerals Wavelength (  m) 2.00 2.10 2.20 2.30 2.40 REFLECTANCE Kaolinite Alunite Buddingtonite AVIRIS Laboratory Spectrometer Kaolinite: Al 4 Si 4 O 10 (OH) 8 Alunite: (K,Na)Al 3 (SO 4 ) 2 (OH) 6

23 Thermal Signatures Emissivity 8.6 Wavelength (  m) 7 8 9 10 11 12 13 Leucogranite Granodiorite Quartz Monzonite Granodiorite Diorite Anorthosite SiO 2 % Quartz% 70.8 29.5 67.8 31.9 64.0 23.7 60.4 18.8 49.7 0.0 54.7 2.2 EMISSSIVITY

24 Thermal Remote Sensing LANDSAT TM 6 DIGITAL VALUE SURFACE WATER TEMPERATURE 110 135

25 Thermal Diurnal Signature 8.8 SAND MEADOW FOREST MEADOW SAND FOREST LAKE SUNRISE NOON SUNSET COOL WARM TEMPERATURE LAKE

26 EARTH WATER DAWN NOON SUNSET MIDNIGHT 6 12 18 0 COOL WARM TEMPERATURE Thermal Diurnal Signature

27 Radar Signatures TIME (Near Range) (Far Range) RETURN INTENSITY IMAGE TONE RADAR SIGNATURE TERRAIN FEATURE SPECULAR (SMOOTH) SURFACE CORNER REFLECTORS DIFFUSE SURFACE SHADOW HIGHLIGHT RANGE (LOOK) DIRECTION AZIMUTH (FLIGHT) DIRECTION DEPRESSION ANGLE TRANSMITTED PULSE


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