Post on 28-Nov-2014
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TO ACQUINT THE CLASS WITH CONCEPTS OF THERMAL REMOTE SENSING
AIM
INTRODUCTIONPRINCIPLES OF THERMAL REMOTE SENSINGTHERMAL SENSORSAPPLICATIONS
CONTENTS
INTRODUCTION
REMOTE SENSING
Remote sensing is an art and science of
acquiring info about an object of interest
without coming in physical contact with it.
Thermal remote sensing is based on the measuring of EM radiation in the infrared region of spectrum.Most commonly used intervals are 3-5 micro-meter and 8-14 micro-meter
THERMAL REMOTE SENSING
Thermal IR and atmospheric window
Landsat 7Band 7
Landsat 7Band 6
Thermal energy emitted from the Earth is trapped by CO2, H2O, and O3.Global Warming!
PRINCIPLES OF THERMAL REMOTE
SENSING
Electromagnetic Radiance (EMR)
EMR – Energy emitted by the objects of which absolute temperature is above zero.The magnitude and spectral range of the emitted EMR are governed by the material’s:
Temperature, andEmissivity
Review of Radiation Laws
All objects at temperature above absolute 0oK emit (-273.59oC, -459.67oF)
Stefan-Boltzmann law: W = sT4 W-total emitted radiation
s-a constant, T-temperature in oK
The total emitted radiation from a blackbody is proportional to the fourth power of its absolute temperature
Radiation Laws
► Wien's displacement law: l = 2,897.8/T l-peak wavelength, T-temperature in oK
► As temperature of objects increases, the wavelength of peak emittance becomes shorter
► Emissivity: e = M/Mb e-emissivity
M-emittance of a given object Mb-emittance of blackbody e = 1 (blackbody) e = 0 (whitebody, perfect reflector)
► The ratio between the emittance of a given object and that of blackbody at the same temperature
Radiation Laws
Emissivity of Common Materials
Clear water 0.98-0.99Wet snow 0.98-0.99Human skin 0.97-0.99Rough ice 0.97-0.98Vegetation 0.96-0.99Wet soil 0.95-0.98Asphalt concrete 0.94-0.97Brick 0.93-0.94Wood 0.93-0.94Basalt rock 0.92-0.96
Dry mineral soil 0.92-0.94paint 0.90-0.96Dry vegetation 0.88-0.94Dry snow 0.85-0.90Granite rock 0.83-0.87Glass 0.77-0.81Sheet iron (rusted) 0.63-0.70Polished metals 0.16-0.21Aluminum foil 0.03-0.07Highly polished gold 0.02-0.03
Water, Ice and Snow
Water, ice, and snow generally have a high emissivity, 0.94 to 0.99, across the thermal infrared region. Snow is unusual in that it has a high reflectance in the solar (visible) region where most of the downwelling energy is during the day, and a very high emissivity in the thermal region.
Water
Ice
Snow
Soil and Minerals
Soil, rocks, and Minerals show strong spectral features between 8 and 10 microns that depend on the grain size. Soil signature in the 3 to 5μm region depends on the water and organic content. The dryer, purer soils have lower emissivities in this region.
Vegetation
Green vegetation typically has a very high emissivity because it contains water. Senescent (dry) vegetation has a more variable emissivity, especially in the 3 to 5μm region, which depends on the type and structure of the cover type, the dryness, etc.
Man-made material
Manmade materials such as polished metals have among the lowest emissivity values, can be made less than 0.01 (better than 99% reflecting). “Rocky” materials such as asphalt and brick are high and range from 0.90 to 0.98
Thermal sensors
TIROS (Television IR Operational Satellite), launched in 1960GOES (Geostationary Operational Environmental Satellite), TIR at 8km spatial resolution, full-disk of Earth, day and nightHCMM (Heat Capacity Mapping Mission), launched in 1978- 600m spatial resolution, 10.5 – 12.6 micron rangeCZCS (Coastal Zone Color Scanner) on Nimbus 7, launched in 1978, for SST (sea surface temperature).AVHRR (Advanced Very High Resolution Radiometer), 1.1 and 4 km TIR bandsTIMS (Thermal Infrared Multispectral Scanner), Airborne, 6 bandsATLAS (Airborne Terrestrial Applications Sensor), 15 bandsLandsat 4,5,7; Band 6- 10.4 – 12.5 m, 120 m (4,5), 60 m (7).ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) on Terra, 5 bands 8.125-11.65 micron range (14 total)
THERMAL SENSORS
Applications
Application Areas
Surface temperature detectionCamouflage detectionFire detection and fire risk mappingEvapotranspiration and drought monitoringEstimating air temperatureOil spill monitoringWater quality monitoringVolcanic activity monitoringUrban heat island analysis
Mars Hematite detected by TES
24.0°F
43.0°F
25
30
35
40
Furnace Vent
Vent Duct
Typical IR imagery of Heat Loss in Residential Structures
Energy Gain (Floor Leak)
Missing Insulation in Vaulted Ceiling Area
Moisture
Heat Loss Heat Loss
37.3°F
46.6°F
38
40
42
44
46
Typical Institutional Building Heat Loss
37.3°F
46.6°F
38
40
42
44
46
37.7°F
50.9°F
38
40
42
44
46
48
50
28.5°F
54.5°F
30
35
40
45
50Typical Air Leak Patterns
37.7°F
50.9°F
38
40
42
44
46
48
50
*>59.3°F
*<43.9°F
44.0
46.0
48.0
50.0
52.0
54.0
56.0
58.0
*>64.4°F
*<44.2°F
45.0
50.0
55.0
60.0
*>64.4°F
*<37.9°F
40.0
45.0
50.0
55.0
60.0 Air Leakagefrom non-insulated areas and window frames.
Processing thermal images
Major issuesMoisture absorption in atmosphereMixed ground objects
Some visualization techniquesFalse color compositeLevel slicing
Sea-surface temperature, June 22, 2000
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Ocean surface temperature from MODIS
QUESTIONS PLEASE !!
Thank You
Thank You