Remote sensing in Civil Engineering

Remote Sensing

Manishkumar Dubey

MANISHKUMAR DUBEY

What is Remote Sensing? "Remote sensing is the science of acquiring information about the Earth's surface without actually being in contact with it. This is done by sensing and recording reflected or emitted energy and processing, analyzing, and applying that information."

1903 - The Bavarian Pigeon Corps

HISTORY

IRS 1C Sensors overview

PAN

LISS III

WiFS

Basic principle of remote sensing

• Most remote sensing system utilizes the suns energy which travel through the atmosphere are selectively scattered observed depending upon the composition of the atmosphere and wavelength involved.

• These radiations reaching earth interacts with the objects. Some of these radiations are absorbed , reflected or emitted back to the sensors and that recorded and processed in the form of image which is then analyzed to extract the information about the objects

• Finally information extracted are applied In decision making and solving particular problem.

Solar Energy

Incident Radiation

Absorption

Scattering

Reflected energy

Thermal emission

Transmission

Platforms & Sensors

Ground Borne

Air Borne

Space Borne

Antenna Data Processing

Data Products Soft Copy

Data Products Hard Copy

Visual Interpretation

Digital Interpretation

Outputs Softcopy

Outputs Hard Copy

Decision Making

Remote Sensing through instrument

Various Platforms

Electromagnetic energy

Electromagnetic energy is a term used to describe all the different kinds of energies released into space by stars such as the sun. these kinds of energy such as 1. radio waves 2. TV waves 3. Radar waves 4. Heat (infrared) 5. Light 6. ultraviolet 7. X-rays 8. Microwaves 9. gamma waves

Longer wavelentgh – lower frequency

Electromagnetic spectrum

Measuring Light: Bands• Human eyes only ‘measure’ visible light

• Sensors can measure other portions of EMS

Bands

Thermal Infra Red Image (TIR )

GEOSTATIONARY ORBITS

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These satellite appears stationary with respect to the Earth's surface. Generally placed above 36,000 km from the earth.

FOOTPRINTS

Communication Satellites are in GEOSYNCHRONOUS ORBIT (Geo = Earth + synchronous = moving at the same rate).This means that the satellite always stays over one spot on Earth. The area on earth that it can “SEE” is called the satellite’s “FOOTPRINT”

A Polar Orbit is a particular type of Low Earth Orbit. The satellite travels a North – South Direction, rather than more common East-West Direction.

• As the satellite revolves around the Earth, the sensor "sees" a certain portion of the Earth's surface.

• The width of the strip imaged is referred to as the swath width.

SWATH

SIX STAGES IN REMOTE SENSING

Stage-1. Source of energyStage-2. Transmission of EMR towards the ObjectStage-3. Interaction of EMR with the ObjectStage-4. Transmission of Interacted EMR towards the SensorStage-5. Recording of the Image by the DetectorStage-6. Analysis of the Imagery

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Types of remote sensing

• Passive: source of energy is either the Sun or Earth/atmosphere – Sun

- wavelengths: 0.4-5 µm

– Earth or its atmosphere- wavelengths: 3 µm -30 cm

• Active: source of energy is part of the remote sensor system – Radar

- wavelengths: mm-m

– Lidar- wavelengths: UV, Visible, and near infrared

Camera takes photo as example, no flash and flash

Active detection1. Active Sensors provide their own energy source for illumination of the target by directing a burst of radiation at the target and use sensors to measure how the target interacts with the energy.

2. Most often the sensor detects the reflection of the energy, measuring the angle of reflection or the amount of time it took for the energy to return.

3. Active sensors provide the capability to obtain measurements anytime, regardless of the time of day or season.

4. They can be used for examining energy types that are not sufficiently provided by the sun, such as microwaves, or to better control the way a target is illuminated. However, active systems require the generation of a fairly large amount of energy to adequately illuminate targets.Doppler radar is an example of an active remote sensing technology.

GROUND PENETRATING RADAR(GPR)

Active Remote Sensing

Sensor Detection1.Passive Detection• sensors measure levels of energy that are

naturally emitted, reflected, or transmitted by the target object.

• Passive sensors are those which detects naturally occurring energy. Most often, the source of radioactive energy is the sun.

• Detection of reflected solar energy, for example, can only proceed when the target is illuminated by the sun, thus limiting visible light sensors on satellites from being used during a nighttime pass.

• The Thematic Mapper, the primary sensor on the Landsat satellites, is a good example of a passive sensor.

Active and Passive Remote Sensing

USUAL PLATFORMS

• Aircraft – Helicopters– Microlites– Low altitude aircrafts– High altitude aircraft

• Satellites– Orbiting satellites– Geostationary satellites

Application of Remote Sensing in civil Engineering

Various civil engineering application areas include 1. Urban/ Regional planning 2. site investigation 3. terrain mapping and analysis 4. water resources engineering 5. town planning and urban infrastructure development, 6. transportation network analysis 7. landslide analysis.Regional Planning and Site Investigations: Site investigations in general require topographic and geologic considerations. Remote sensing data permits such an assessment. In case of dam site investigation, information on topography is essential. Geological consideration involves the different soil and rock types and physical properties

Image source: www.ldeo.columbia.edu

Image source: www.geospectra.net

• In selecting river-crossing sites for bridges and pipelines, an important consideration is the stability of slopes leading down to and up from the water crossing. Such slopes include riverbanks, terrace faces and valley wall. History of river erosion and sedimentation would give clues needed for locating the sites where scour is likely to occur. High spatial resolution satellite data with stereo vision capability can facilitate depth perception in the above said investigations and also for regional planning of large commercial airports, harbors, industrial towns and recreational sites.

• The hydro geological and geomorphologic information along with geological structures derived from satellite data are very useful in sitting the ground – water bore holes.

• Terrain Mapping and Analysis Assessment of the performance of the terrain for specific developmental activities can be made through terrain evaluation. For this, terrain information can be acquired from RS data and by generating the Digital Terrain Model

• In engineering construction like dam, the knowledge of material comprising the terrain is essential for proper planning, location, construction and maintenance of engineering facilities.

• For computation of hydrograph parameters like peak runoff rate, time of concentration and time to peak, the height and slope information derived from Digital Elevation Model (DEM) are useful.

• In large area reconnaissance studies, various technically feasible and economically viable alternatives in locating surplus flow diversion routes to water deficient basins can be arrived at.

• projects of large dimensions require considerations of land use / land cover, soil and geological mapping, terrain evaluation, construction material inventory etc. the latter are derived from satellite remote sensing data of particular resolution depending upon the scale on which such information is required

Advantages of Remote Sensing• Provides a view for the large region• Offers Geo-referenced information and digital

information• Most of the remote sensors operate in every

season, every day, every time and even in real tough weather

• Easy acquisition of data over inaccessible areas• A single data can be used for different uses

SATELLITE REMOTE SENSING APPLICATIONSAGRICULTURE• CROP PRODUCTION ESTIMATION SOIL RESOURCES• SOIL MAPPING• LAND CAPABILITY, LAND IRRIGABILITY• SOIL MOISTURE ESTIMATION• MAPPING WATER-LOGGED AREAS • SALT-AFFECTED SOILS, ERODED LANDS, SHIFTING CULTIVATION LANDUSE/LAND COVER• LAND USE/LAND COVER MAPPING • WASTELAND MAPPING GEOSCIENCES• GROUND WATER POTENTIAL ZONE MAPPING• MINERAL TARGETTINGFORESTRY AND ENVIRONMENT• FOREST COVER MAPPING• FOREST MANAGEMENT PLAN - RS INPUTS• BIODIVERSITY CONSERVATION• ENVIRONMENTAL IMPACT ASSESSMENT• GRASSLAND MAPPING

Natural Resources

SATELLITE REMOTE SENSING APPLICATIONSWATER RESOURCES• SNOWMELT RUNOFF FORECASTING• RESERVOIR SEDIMENTATION

OCEAN APPLICATIONS• COASTAL ZONE MAPPING• POTENTIAL FISHING ZONE (PFZ) MAPPING• CORAL REEF MAPPING

DISASTER ASSESSMENT• FLOOD / CYCLONE DAMAGE ASSESSMENT• AGRICULTURAL DROUGHT ASSESSMENT• VOLCANIC ERUPTION, UNDERGROUND COAL

FIRE• LANDSLIDE HAZARD ZONATION• FOREST FIRE AND RISK MAPPING

INTEGRATED MISSION FOR SUSTAINABLE

DEVELOPMENT• SUSTAINABLE WATERSHED DEVELOPMENT

URBAN APPLICATION

ENGINEERING APPLICATIONS

Infrastructure

Flood due to cyclone (29th October 1999) off Orissa coast

IRS LISS IIIPre-cyclone (11.10.99)

IRS LISS IIIPost-cyclone (05.11.99)

RADARSATDATA of 2nd NOV

Snow and Glacier Monitoring

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Vegetation/Forests/Agriculture

Kharif-1999 (Sep-Oct) Rabi-2000 (Feb-Mar)

Applic

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Mapping and monitoring mangroves, coastal wetlands

PP

PKRISHNA R.

IRS-1B LISS-I IMAGE, 1992

KRISHNA R.

P = Prawn cultivation IRS-1C LISS-III IMAGE, 2000

• ROCK TYPES• GEOLOGICAL STRUCTURES (LINEAMENT /FAULT/DYKE)• VALLEY FILL WITH VEGETATION• BLACK SOIL COVER• SALT AFFECTED LAND

WHAT CAN BE SEEN FROM SATELLITE IMAGES?

• HILLY TERRAIN WITH FOREST• AGRICULTURAL LANDS - DELTA• RIVER COURSES• COASTLINE

WHAT CAN BE SEEN FROM SATELLITE IMAGES?

• MANGROVE FOREST • WET LANDS• WATER TURBIDITY

Land UseLand cover means any surface cover on the ground which can include vegetation, urban infrastructure, water, lake, mountain, transportation networks, buildings or any other. The attributes measured by remote sensing techniques relate to land cover, from which land use can be inferred, particularly with ancillary data or a priori cognition.

Application of Remote Sensing

MappingGenerating different maps from remotely sensed data can be so effective ad valuable. A classification of sensing elements and methodologies to generate theses remotely sensed models are essential for mapping. Two primary methods of generating elevation data are: 1. Stereogrammetry techniques by air photos 2. Radar interferometry

Radar image of a continuously clouded area

Map with the road network

Wageningen UR 2002

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But may be easier than we think…to use Technology

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