ROHIT KUMARCUJ/I/2013/IGIO/026SEMESTER-5th

Contents:

• Introduction

• Thermal IR And Atmospheric Window

• Fundamental Radiation Laws

• Atmospheric Effects

• Thermal Data Acquisition

• Applications

• Advantages & Disadvantages

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

• Thermal remote sensing is the branch of remote sensing that

deals with the acquisition, processing and interpretation of data

acquired primarily in the thermal infrared (TIR) region of the

electromagnetic (EM) spectrum. In thermal remote sensing we

measure the radiations 'emitted' from the surface of the target, as

opposed to optical remote sensing where we measure the

radiations 'reflected' by the target under consideration.

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 IR and atmospheric window:

Landsat 7

Band 7Landsat 7

Band 6

Thermal Infrared Spectrum:

Thermal IR: 3 – 14 μm

Near IR: 0.7-1.3 μm

Mid IR: 1.3 – 3.0 μm

Fundamental Radiation Laws:

The following laws are obeyed in this phenomenon:

Planck’ Radiation (Blackbody Law)

Wein’s Displacement Law

Stefan-Boltzman Law

Atmospheric Effects:

• The atmospheric intervention between the thermal sensor and the ground can modify the apparent level of radiations coming from ground depending on degree of atmospheric absorption, scattering and emission.

• Atmospheric absorption & scattering make the signal appear colder and atmospheric emission make the object to be detected as warmer.

• There are some factors on which both of these effects depend upon given by:

Atmospheric path length

Meteorological conditions

Site

Altitude

Local weather condition

Thermal Image Acquisition:

• Many multispectral (MSS) systems sense radiations in the thermal infrared as

well as the visible and reflected infrared portions of the spectrum.

Thermal Sensors:

• Thermal sensors use photo detectors sensitive to the direct contact of

photons on their surface, to detect emitted thermal radiation.

• The detectors are cooled to temperatures close to absolute zero in order to

limit their own thermal emissions.

• Thermal sensors essentially measure the surface temperature and thermal

properties of targets.

THERMAL SENSORS:

TIROS (Television IR Operational Satellite), launched in 1960

GOES (Geostationary Operational Environmental Satellite), TIR at 8km spatial resolution, full-disk of Earth, day and night

HCMM (Heat Capacity Mapping Mission), launched in 1978- 600m spatial resolution, 10.5 – 12.6 micron range

CZCS (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 bands

TIMS (Thermal Infrared Multispectral Scanner), Airborne, 6 bands

ATLAS (Airborne Terrestrial Applications Sensor), 15 bands

Landsat 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).

Applications:

Surface temperature detection

Camouflage detection

Forest fire detection and fire risk mapping

Evapotranspiration and drought monitoring

Estimating air temperature

Oil spill monitoring

Water quality monitoring

Volcanic activity monitoring

Urban heat island analysis

Military purpuses

Thermal Remote Sensing Of Forest Fires:

Detection of active fires provides an

indicator of seasonal, regional and inter

annual variability in fire frequency and

shifts in geographic location and timing

of fire events.

NASA's Ikhana Unmanned Research Aircraft Recorded Image of Fire Near Lake in Southern California:

• The 3-D processed image is a colorized mosaic of

images draped over terrain, looking east.

• Active fire is seen in yellow, while hot, previously

burned areas are in shades of dark red and purple.

• Unburned areas are shown in green hues.

Volcanism in Thermal Remote Sensing:

Active volcanoes exhibit many difficulties in

being studied by in situ techniques.

For example, during eruptions, high altitude

areas are very hard to be accessed because of

volcanic hazards.

We use thermal remote sensing techniques in

mapping and monitoring the evolution of

volcanic activity.

Aster Image:

• Size: 7.5 x 7.5 km

• Orientation: North at top

• Image Data: ASTER

bands.

Most Active Volcanoes:

• True Color Image Thermal Image

Thermal remote sensing in Military:

Due to their ability to detect man sized targets at extremely long

distances, in total darkness and in extreme weather conditions thermal

imaging cameras are extremely suited for boarder surveillance.

Generally, cooled cameras are used in border security applications as

they provide range performance than un-cooled detector.

If the terrain is e.g. mountainous and does not permit seeing over a

distance of 20 kilometers, un-cooled thermal imaging cameras can be

used for border security as well.

Thermal imaging cameras can be integrated with radar systems.

Advantages & Disadvantages:

Advantages

We can detect true temperature of

objects.

Feature cannot be detected by optical

RS may be detected with Thermal IR.

Disadvantages

It is pretty difficult to maintain the

sensors at required temperatures.

Image interpretation of thermal

image is difficult.

References:

“Remote Sensing of the Environment ” , John. R Jensen, Edition 6th.

“Remote Sensing and Image Interpretation ” , Thomas M. Lillisand, Ralph W. Kiefer, Jonathan W. Chipman, Edition 6th.

www.geog.ucsb.edu/~jeff/.../remote sensing/thermal/thermalirinfo.html

earth.esa.int/landtraining09/D1Lb3_Su_SEBBasics.pdf

en.wikipedia.org/wiki/Remote_sensing