Remote Sensing in Geology

Lesson 1:Definition and scope of Remote

SensingBrief history

Lesson 2:RS systemElements of the RS system

Lesson 3:Resources

Lesson №4

Nature and effects of EME interaction with the atmosphere & Earth materials

Color & color models

• Why the interaction?First of all, we are dealing with structured matter, usually crystallized, i.e. ordered in a crystal lattice. In its knobs there are the atoms or atom groups called “ligands”, interrelated and hold together by inter-atomic forces. So, the EME incident upon it, could interact at different levels of such structure…

ligands(atoms, ions

&c)

inter-atomic bonds

Interactions of EME with material structure

Further on, these materials are performing some effects

while interacting with the EME (absorption, emission...)

This is exactly why we are interested in interaction, because on the basis on these effects we are able to find out something about the chemical composition and structure of the material (studying the spectral signature of the sample).

Interactions of EME with material structure

• Interaction and spectra modelγ, X, UV, V+NIR+SWIR, TIR

| B

lue G

reen

|

R

ed

|γ

nucleus

X

inner shell

SWIR

NIRV

UV

outer shell

TIR

inter-atomic bonds

Interactions of EME with material structure

• Physical background:

- Black body radiation in brief, would be a theoretical idealization of the natural (real) body radiation. It determines the temperature rate (the energy of radiation), which is propagating through a specific EME range (wavelengths)

- Kirchoff’s law (emission equalsthe absorption and converse thereflection)

- The basic plots of spectral signatures involves either reflectance, absorbance, transmittance or radiance vs. wavelength

Interactions of EME with atmosphere and Earth materials

• Energy states involves:

Etotal=Etrans+Erot+Evibr+Eelactronic

• Vibrational processes due to the bond “elastics” in crystal lattice exhibit emission in SWIR and TIR

• Electronic processes include mentioned transitions of energy levels of charged particles – electrons surrounding the nucleus (excitation and deexcitation). Moreover, it can include some puzzling phenomena due to the influence of crystal lattice geometry for example.

* all of the minerals are containing Fe3+ (ferrous ion) but it depicts different absorption bands in NIR+SWIR

Interactions of EME with atmosphere and Earth materials

• Atmospheric effects- scattering:

non-selective: due to the solid or fluid particles much larger than the λ involved. Since it scatters uniformly at all λ the object (cloud, fog, dust &c) appears white.

selective scattering: appears at molecular level and tends to increase as λ decreases, so it impacts visible blue and UV region in abundance, while IR is for example completely intact (the blue skies effect). Provokes high path radiance in blue and UV region.

- absorption: remember the atmospheric windows story (primarily due to H2O, O2-3 and CO2)

- emission: due to their energy state, the particles in the atmosphere can emit discrete bands which are corresponding to high absorption or high opacity regions :) no trouble for RS!

• Their overall, reflected or emitted outward (to the sensor) is the path radiance (obscuring the ground radiance as background noise)

Effects of EME interactions atmosphere and Earth materials

• Ground effects- Reflection:

ER=EI –EA–ET or reflectance (albedo, when wide range) R=ER /EI

Basic types: specular, Lambertian (diffuse), real (semi-diffuse)

Superficial and volume raysSource angle (bigger the angle bigger the scattering)Grain size effect!

Effects of EME interactions atmosphere and Earth materials

- Transmission:causes simple conduction (homogenous materials) and volume scatter (with inhomogeneous ones). Those two types are opposed to surface scatter in the function of wavelength, e. g. water bodies and dry rock in V & MW (the MW oven, 12 cm)

- Absorption

- Emission(black body)3,4 μm peak300 K

Effects of EME interactions atmosphere and Earth materials

• Spectroscopy uses spectrometers for theground investigation of the samples (Earth materials), resulting in reflectance curves aka spectral signatures (finally we exploit their features such as sharpness, deepness, shouldering, rounding, shallowness, openness &c to discover the ground properties )

• The RS sensors capture some portions (limited by atmospheric windows) of the Earth material spectra, but it turns out that it is sufficient for many purposes.

• Spectroscopy vs. remote sensing

Interactions of EME with atmosphere and Earth materials

• What is the color?A spectral response of EME in visible domain which is experienced through the sensing system of our own.

Extendable? Why not?! Make the invisible visible using the RS sensors!

• The color has been systematically ordered in several ways:- RGB color model- HIS color model

Color

• RGB (Red Green Blue) model

Basically, a 3D-reference system (Cartesian)scaling from 0 to 255 (total of 256 values for the 8-bit image information) containing 3 basic blends of visible realm.

• Convenient for simple math operations (±)R+G+B=WW–G=R+B=CW–B=G+R=YY+M+C=?W–B+W–G+W–R=3W–WW–W=BLACK

• Having a result does not allow us to predict how it was generated

Color

• HIS (Hue Intensity Saturation) modelResembles the actual properties of light(wavelength, intensity and radiance corresponds to HIS)

• Compatible with RGB over many relations such as:

Color