#separator:tab #html:true Speed of Light 3 * 108 m/s Steffan-Boltzmann equation W = \(\sigma T^4\)

W: total emitted radiation energy (as watt m-2)
\(\sigma\) is the SB constant
T: in K
greybodies: * \(\epsilon\) (emissivity)

for blackbodies
hot bodies emit more energy per unit area than cold Wien's Law wavelength in \(\upmu m\) where radiance is max
as objects become hotter, wavelength of max emittance shifts to shorter wavelengths

\(\uplambda_{max}\) = 2897.8 / T
Remote sensing (define) Science and art of deriving information about an object without touching it, or: the practice of deriving information about the earth’s land and water surfaces using images acquired from an overhead perspective, using electromagnetic radiation in one or more regions of the electromagnetic spectrum, reflected or emitted from the earth’s surface. Temporal resolution imaging revisit interval (eg every 16 days) Spatial resolution Pixels: sensor limitation to size of smallest ground area that can be separately recorded on an image (eg 10x10 m) Radiometric resolution Ability of a remote sensing system to record many levels of values

(7, 8, 9, 10-bit...) Land resource satellite images AVHRR, Landsat, ERS/ Radarsat, IKONOS Digital Number the value of pixels
representing intensity (magnitude) of electromagnetic energy

+ve binary digits (8-bit image = 2^8=256, so 0-255 color levels) Grey level Wavelength vs frequency are inversely related

c = \(\uplambda\)v

where
u: Radiant energy Total radiation energy (J) u: Radiant energy flux radiant energy per unit time
J/sec = W u: Radiant flux density radiant flux per unit surface area

J(m2 * s) = W/m2 Irradiance radiant flux density: fluxes to/ from a flat surface in all directions

(same units: J/ m2 * s) u: Spectral irradiance irradiance per unit wavelength

J/(m2 * s * \(\upmu\)m) Reflec{tance,ivity} Reflected irradiance / Total incoming irradiance

is unitless Absorp{tance,tivity} absorbed irradiance / total incoming irradiance

unitless Transm{ittance,issivity} transmitted irradiance / total incoming irradiance

unitless Radiation conservation law absorption + reflection + transmission = incoming radiation Plank's law (what) distribution of emitted radiant energy for different wavelengths

higher energy, higher emits
higher temp, lower wavelengths when peak ocurrs

radiation (wavelength?) emitted by blackbody at a certain temperature ES: Visible light spectrum colors 400-700nm

Violet, Blue, Green, Yellow, Orange, Red ES: Ordering Gamma Rays, X-rays, UV, Visible, Infrared, Microwave, Radio ES: Gamma rays - 0.03 nm ES: X-rays 0.03 nm - 300 nm ES: UV 300 nm - 380 nm ES: Infrared 720 nm - 15.0 \(\upmu m\) ES: Microwave 15.0 \(\upmu m\) - 30 cm  ES: Radio 30 cm - kelvin, celcius k = 273.15 + c Emmisivity \(\epsilon = M/M_b\)

emmited irradiance of a given object / emitted irradiance of a blackbody
ratio, at the same temperature
measure of effectiveness of an object as a radiator of electromagnetic energy What does scattering do? Decreases quality of an image Rayleigh Specks of dust, N_2, O_2 molecules

Strongly wavelength dependent Mie Dust, pollen, smoke, water droplets

Weakly wavelength dependent Nonselective Large water droplets, large particles of airborne dust

Wavelength independent atmospheric absorption absorption of radiation occurs when atmosphere prevents transmission of radiation (or its energy) through atmosphere absorption causing gases ozone (O_3)
carbon dioxide (CO_2)
Water vapour (H_2O) atmospheric windows UV and visible
near infrared
mid-infrared
Thermal IR
Microwave Radiance < - > Irradiance I: radiant flux density: Jm-2s-1 
R: radiant flux density per unit sold angle Jm-2 s-1 sr-1 

For a diffuse reflector (Lambertian surface): I = \(\pi R\)
Selective, non-selective transmitters non-selective: same colour active sensor generates, emits radiation to the surface, receive the returned signals

inc. active microwave (RADAR), Laser, ... passive sensors receive reflected or emitted signals from the surface, inc.
optical, thermal, and passive microwave sensors LANDSAT: Band 1 (Blue-Green) - soil/vegetation distinction
- cultural/urban feature ID
- penetration of clear water LANDSAT: Band 2 (Green) - green vegetation
- cultural/urban feature ID
- reflectance from turbid water LANDSAT: Band 3 (Red) - Plant chlorophyll absorption
- Cultural/ urban feature ID LANDSAT: Band 4 (Near-Infrared) - ID plant/ vegetation types, health, biomass content
- Water body delineation
- Soil moisture LANDSAT: Band 5 (Mid-Infrared) - Sensitive to moisture in soil and vegetation
- Discriminationg snow/ cloud-covered areas
- Penetration of thin clouds LANDSAT: Band 6 (Far-Infrared) - Relative brightness temperature
- Vegetation stress and soil moisture discrimination related to thermal radiation
- Thermal mapping (urban, water) LANDSAT: Band 7 (Mid-Infrared) - Discrimination of mineral and rock types
- Hydroxyl ion absorption
- Sensitive to vegetation moisture content