applications of rs_gis to geology [compatibility mode]

Consultancy Unit

GIS/REMOTE SENSING WORKSHOP 2012

Consultancy Unit GIS/Remote Sensing Workshop 2012

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1. Introduction Remote Sensing Geographic Information System Geology2. Why Use RS/GIS3. Areas of Application4. Photo-geology5. Imageries6. Surface Mapping7. Subsurface Mapping

Consultancy Unit GIS/Remote Sensing Workshop 2012 3

Is the science and technology by which the characteristics ofobjects of interest can be identified, measured or analyzedwithout direct contact.

A device to detect the electromagnetic radiation reflected or emitted from an object is called a "remote sensor" or "sensor". Cameras or scanners are examples of remote sensors.

A vehicle to carry the sensor is called a "platform". Aircraft or satellites are used as platforms



A. Energy SourceB. AtmosphereC. TargetD. SensorE. Transmission, reception

and processingF. Interpretation/AnalysisG. Application

This is done by sensing and recording reflected or emitted energy and processing, analyzing, and applying that information


Remote Sensing is classified into threetypes in respect to the EM wavelengthregions

Visible (VIS) and Reflective Infrared (IR) Remote Sensing.

Thermal Infrared (TIR) Remote Sensing. Microwave Remote Sensing.


An integrated set of computer hardware and software for spatial data:

o Collectiono Storageo Structuringo Manipulationo Analysis o Visualisation

Referenced by geographic co-ordinates X, Y, Z coordinates can be used to represent different

parameters, ie longitude, latitude, elevation Data is stored in raster images (pixels) and vectors using

dots, lines and polygons


Means study of the Earth (structure, composition,processes, etc)

Geological mapping entails the representation of geologicalfeatures on maps

Features can be represented by points, lines and polygons the so-called GIS primitives

Geological features may include rock units, bedding planes,folds, faults, lineation, foliation, etc

Geologic mapping may be done on the surface and/or thesubsurface


Traditional mapping techniques slow and expensive. Earthscientists increasingly searching for cost-effective and rapidtechniques of geological data gathering

Remotely sensed imageries show spatial relationships of minerals and structures

Enables continues acquisition of data temporal resolution Offers a wide regional coverage (synoptic view) with good

spectral resolution Allows the mapping of inaccessible and difficult terrains, eg

the Mambila plateau, Oban massifs, etc

With GIS, maps can now be updated easily, interpreted andcompared

There is a faster access to data Maps can now be combined in layers, eg topography,

minerals, hydrology, etc Geologists can now provide information in map form that is

easily interpreted by non-geologists Provides capability for the integration, visualization,

enhancement, and interpretation of multiple geo-data setsin a GIS environment


Mapping of major geologic units Recognition of certain rock types Mapping landforms (geomorphology) Search for surface guides to mineralization Determination of regional structures Geo-hazard mapping, eg flood mapping/monitoring Sedimentation mapping and monitoring Structural mapping Planetary mapping Environmental geology eg oil spill extent and drift Lithological mapping and geo-botany

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Picking out rock units Studying geo-morphology (the expression and modes of the

origin of landforms) Determining the structural arrangements of disturbed rock

strata (folds and faults) in structural geology. Evaluation of dynamic changes from natural events, ie,

geologic hazards (eg Earthquakes, floods, volcaniceruptions, landslides, etc)

Seeking surface clues (such as alteration and other signs ofmineralization) to subsurface deposits of ore bodies,hydrocarbon explorations, and hydro-geologic interests.

Functions as a base on which a geologic map is drawnConsultancy Unit GIS/Remote Sensing Workshop 2012 15

The advantage of large area or synoptic coverage permitsthe assessment in single scenes (or in mosaics) thegeological representation of Earth on a regional basis

The ability to analyze multispectral bands quantitatively interms of numbers (DNs) allows for processing routines thatdiscern and enhance certain compositional properties ofEarth resources

Tool for recognizing faults and other known structural trends, eg lineaments and folds

They reveal regional geologic settings and are easilyenhanced by digital processing


Interpretation of surface geology using RS images allows inference of what may lie below

Imaging Spectrometry They acquire images in a large number of spectral bands

(more than 100) These bands are narrow and contiguous (adjacent) Therefore they enable the extraction of reflectance spectra

at pixel level Can be used in surface mineralogy mapping to aid in ore

exploration, lithologic mapping, structural mapping,environmental geology eg acid mine drainage and minewaste monitoring, etc


Geologic phenomena are typically spread over wider scenes, so that the ability to see the regional picture is a powerful attribute of space imagery

However, this view is somewhat hindered by theinterference of soil and vegetative cover

Other methods are required that can probe more deeplyinto the ground by making use of the physical or chemicalproperties of the buried rocks

These properties or changes in properties from one rocktype to the another are detected by carrying outgeophysical surveys with sensors such as gravimeters,magnetometers and seismometers


Gamma radiation (electromagnetic radiation of very short wavelength)arises from the spontaneous radioactive decay of certain naturallyoccurring isotopes

They have enough energy to penetrate a few hundred meters of air,hence may be detected conveniently from a low-flying aircraft

Only 3 isotopes lead to the emission of gamma rays when they undergotheir radioactive decay: Thorium (Th), Uranium (U) and Potassium (K)

Each rock unit has a relative abundance of Th, U, and K that is distinctfrom that of adjacent rock units

If the abundance of each of these elements is imaged as a primarycolour and combined in a visual display, each rock unit appears with itsown characteristic hue

The changes in the hue in such an image correspond to geologicboundaries


The Earth has a gravity field and a magnetic field. Rocks that have abnormal density or magnetic properties distort the

gravity and magnetic field of the Earth, producing local gravity andmagnetic anomalies.

Careful and detailed mapping of these anomalies over any area revealspatterns that are related to the structure and composition of thebedrock geology

Satellites equipped with GPS gravimeters allow for efficient and cost-effective way to map gravity

Mapping of magnetic anomalies (called aeromagnetic surveys) fromlow-flying aircraft (equipped with magnetometers) has been widely usedin commercial exploration for ore.

Both methods provide windows on the geology even when concealedby cover formations such as soil, water, sediments and vegetation


Ground-based electrical sounding and profiling permit mapping of subsurface electrical conductivity

Where the ground is stratified an electrical sounding can beinterpreted to reveal the layering in terms of the resistivity orconductivity of each layer

Electromagnetic (EM) methods, however, require no electrical contactwith the ground and can therefore be operated from an aircraft,increasing the speed of survey and the uniformity of the data coverage

Current is induced to flow in the ground by the passage of analternating current through a transmitter coil on board

EM surveys developed largely by the mineral exploration communitysince many important ore bodies, eg sulphide ores, are highlyconductive and stand out clearly from their host rocks through electricalimaging


When RS is used for mapping, knowledge beforehand of particularminerals likely in the sensed scene is beneficial

Thus when an area is being surveyed for specific mineral content (as inexploration for ore minerals), this information aids in identifying themineral species being mapped

Some imageries used in geologic mapping include:1. Radar image penetrates thick clouds and vegetation to about 10cm

of the subsurface2. Total Magnetic Intensity (TMI) detects both shallow and deep-seated

structures such as lineaments3. Radiometric airborne survey that detect radiation from sources4. Landsat TM multispectral images at 30m resolution that extracts

surface lineaments and topographic features

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applications of rs_gis to geology [compatibility mode]

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