Lithological and Structural Mapping Using Satellite Data Mohamed Abdelsalam Missouri S&T.

Lithological and Structural Mapping Using Satellite Data

Mohamed AbdelsalamMissouri S&T

Vision

• Vision is the ability to recognize shapes, patterns and colors and to detect and estimate motion, distance and size

• The eye has evolved independently in many animals groups such as the composite eye of insects and that of our own

• The perceptual ability of human beings are learned entirely through experience

Vision - The structure of the Eye

• The cornea for refraction• The iris for controlling the pupil

diameter to control the amount of light gathered and the depth of field

• The lens with 17 mm focal length to adjust focus for objects at different distances

• The retina (180˚ field of view) is a light-sensitive spherical surface where inverted image are formed through receptors known as rods (130 million) for black and white images) and cones (7 million for color images) www.vrmny.com/anatomy.htm

Rods and Cones

• Rods peaks at about 20˚ away from the fovea and gradually fall off in number towards the edge of the retina

• Cones contains pigments sensitive to red, green and blue and are concentrated immediately around the fovea

• The blind spot where the optic nerve leaves the eye (the blind spot) there are neither rods nor cones

Electromagnetic Spectrum

Additive Primary Colors• Additive primary colors:

– Red

– Green

– Blue

• In equal portions other spectral color are produced:

– Red+Green=Yellow

– Red+Blue=Magenta

– Green+Blue=Cyan

– Red+Blue+Green=White

• In non equal portions non-spectral colors are produced

Subtractive Primary Colors• Additive subtractive colors:

– Magenta

– Cyan

– Yellow

• In equal portions other spectral color are produced:

– Magenta+Yellow=Red

– Magenta+Cyan=Blue

– Yellow+Cyan=Green

– Magenta+Cyan+Yellow=Black

• In non equal portions non-spectral colors are produced

Hue-Saturation-Intensity

• Hue is the nature of the color and can be described by the wavelength. Red = 0˚ or 360˚, green = 120˚, and blue = 240˚

• Saturation = Purity of the color. Zero is completely impure and 90˚ is completely pure

• Intensity Level, or Value is the grayscale In 8 bit radiometric resolution scheme, Zero is black and 255 is white.

Hue-Saturation-Intensity

Color Cube for Additive and Subtractive Primary Colors

Color Cube for Additive Primary Colors and H-S-I

• Color cube for Additive additive primary colors and H-S-I defines the relationship between Red-Green-Blue color space and Hue-Saturation-Intensity color space

• The H-S-I color space is defined by a cone extending from black (0,0,0) to white (255,255,255) in 8 bit radiometric resolution scheme

• The Hue is defined by an angle in which Red=0˚ or 360˚; Green=120˚; and Blue=240˚

• Saturation ranges between 0˚ for completely impure color and 90˚ for completely pure color

Band 3

Band 2

Band 1

RGB color combination images

Color Triangle for Additive and Subtractive primary Colors

• Color triangle for additive and subtractive primary colors illustrates the relationship between Red-Green-Blue and Magenta-Cyan-Yellow

• The triangle corners are occupied by Red, Green and Blue whereas the mid-points between these corners are occupied by Magenta, cyan and Yellow

• The center of the triangle is occupied by white which resulted from the sum of equal portions of Red, Green and Blue

Examples1: Density Slicing

The Beddaho Alteration Zone,

Eritrea

Examples2: Synthetic Color

ImagesThe Nubian Nile,

Sudan

SIR-C/X-SAR dataScattering Mechanisms

Smooth Surface

Rough Surface

Outstanding Relief

Reflection Back- Scattering

Volume- Scattering

Double- Bounce

Penetration

Paleo-channel

SIR-C/X-SAR dataPenetration

Rough sand/bedrock

interfaceSmooth

sand/paleo-channel interface

Paleo-channel (Filled with alluvium)

Fine, well sorted dry sand

(~2 m thick)

Bedrock (Cretaceous sandstone or

Neoproterozoic crystalline basement)

Reflected signal from the

air/sand interface

Back-scattered signal from the sand/bedrock

interface

Complete signal

attenuation

Refracted and Wavelength-reduced

signal through the air/sand interface

Reflectedsignal fromthe sand/

paleo-channelfill interface

The Nile System

Present land above 500 m

PostulatedTrans-African Drainage

LakeMega- Chad 800 km

Present drainage

Modified after Burke & Wells (1989)

Nile

Niger

Zaire

Did the Drainage of NE Africa once flow to the Atlantic?

~ Oligocene (30 Ma)

Examples3: Data FusionThe Erta Ale

Volcano, Ethiopia