CONCEPTS AND FOUNDATION OF REMOTE SENSING HOW REMOTE

CONCEPTS AND FOUNDATION OF REMOTE SENSING

HOW REMOTE SENSING WORKS • Illumination (source) • Radiation and the atmosphere(passing through atmosphere twice) • Interaction with target • Recording of energy by sensor • Transmission, reception or processing

ELECTROMAGNETIC SPECTRUM(EMR)

EMR ranges from shortest (gamma and xray)to longest wavelengths(ra dio and microwaves)

WAVELENGTHS( VISIBLE PORTION) • The light our eyes or remote sensors can detect becomes the part of remote sensing • Wavelength ranges from 0. 4 to 0. 7 micrometer

WAVELENGTHS (VISIBLE PORTION) colours Wavelength range violet 0. 4 - 0. 446 Blue 0. 446 -0. 500 Green 0. 500 -0. 578 Yellow 0. 578 -0. 592 Orange 0. 592 -0. 620 red 0. 620 -0. 7

WAVELENGTHS(INVISIBLE PORTION) • A lot of radiation that our eyes cant detect (invisible) but can be detected by the sensors that also become part of remote sensing e. g • IR (0. 7 to 100 micrometer) Reflected IR ( 0. 7 -3. 0 micrometer) Thermal IR (3. 0 -100 micrometer) The recent interest for RS is Microwaves (1 mm to 1 m)

COLOURS • Primary colours RGB

COMPONENTS OF RS • • • Energy source Platforms Sensors Detectors processing

INTERACTION WITH THE TARGET a)Absorption (by gases, ozone best absorber of UV) b)Scattering • Rayleigh scattering ( upper surface, particles size< incident wavelength, blue sky) • MIE scattering (particles size=incident wavelength, dust, smoke, water droplets, (dark appearance of sky)) • Non-selective scattering (particles size>incident wavelength, as aerosoles, happens in lowest portions of atmosphere, causes haze, fog, white clouds, c)Transmission

INTERACTION WITH THE TARGET • Atmospheric windows : where portions of EM spectrum can pass through the atmosphere. • Atmospheric blinds ….