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!

CERES—Cloud-Earth Radiant Energy System

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

(Wikipedia – Infrared)

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

47

Ocean surface temperature from MODIS

QUESTIONS PLEASE !!

Thank You

Thank You