surveying ii ajith sir class6

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Two Generic Types of Sensors A "passive" system generally consists of an array of small sensors or detectors which record the amount of electro-magnetic radiation reflected and/or emitted from the Earth's surface. An "active" system propagates its own electro-magnetic radiation and measures the intensity of the return signal.

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Page 1: Surveying ii ajith sir class6

Two Generic Types of Sensors

A "passive" system generally consists of an array of small sensors or detectors which record the amount of electro-magnetic radiation reflected and/or emitted from the Earth's surface.

An "active" system propagates its own electro-magnetic radiation and measures the intensity of the return signal.

Page 2: Surveying ii ajith sir class6

Examples of Passive Sensors

Advanced Very High Resolution Radiometer (AVHRR)- Sea Surface Temperature

Sea-viewing Wide Field-of-View Sensor (SeaWiFS)- Ocean Color

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Why Sea-Surface-Temperature?

Sea surface temperature (SST) is a key parameter for energy transfer between the oceans and the atmosphere and AVHRR-derived SST can deliver important data to meteorological and climatological models.

AVHRR imagery is also useful for meteorological applications (for example, providing detailed imagery of cloud systems), and land applications such as vegetation mapping and monitoring.

Page 4: Surveying ii ajith sir class6

Advantages of passive microwave remote Advantages of passive microwave remote sensingsensing

• Sees through clouds at lower frequencies• Long heritage, various instruments since 1978• Emissivity sensitive to state of surface, particularly

moisture– Soil moisture

– Snow-water equivalent

– (water is ~80× as absorptive as ice at these frequencies, whereas in visible through infrared, water and ice have similar absorption coefficients)

• But, because of small amount of energy emitted, pixel size must be large

Page 5: Surveying ii ajith sir class6

ACTIVE SENSORS (Detect the reflected or emitted

electromagnetic radiation from natural sources.)

PASSIVE SENSORS (Detect reflected responses from objects that

are irradiated from artificially-generated energy sources such as radar.)

Passive

Non-Scanning

Non-Imaging. (They are a type of profile recorder, ex. Microwave Radiometer. Magnetic sensor. Gravimeter. Fourier Spectrometer.

Imaging. (Example of this are the cameras which can be: Monochrome, Natural Colour, Infrared etc.)

Scanning

Imaging. Image Plane scanning .Ex. TV Camera Solid scanner.

Object Plane scanning. Ex. Optical Mechanical Scanner Microwave radiometer.

Active

Non-Scanning

Non-Imaging. (They are a type of profile recorder, ex. Microwave Radiometer. Microwave Altimeter. Laser Water Depth Meter. Laser Distance Meter. Scanning

Imaging. (It is a radar ex. Object Plane scanning:

Real Aperture Radar.

Synthetic Aperture Radar.

Image Plane Scanning:

Passive Phased Array Radar.

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IoE 184 - The Basics of Satellite Oceanography. 1. Satellites and Sensors

Sensors on satellites

Passive sensors Wavelength

Information

Visible wavelength radiometers

400 nm - 1 m Solar radiation reflected by Earth surface

Infrared (IR) radiometers about 10 m Thermal emission of the Earth

Microwave radiometers 1.5 - 300 mm Thermal emission of the Earth in the microwave

Active devices

Altimeters 3 - 30 GHz Earth surface topography

Scatterometers 3 - 30 GHz Sea surface roughness

Synthetic aperture radars

3 - 30 GHz Sea surface roughness and movement

Page 7: Surveying ii ajith sir class6

Microwave Remote Sensing: Principles and Applications. Advantages

Day/night coverage. All weather except

during periods of heavy rain.

Complementary information to that in optical and IR regions.

Disadvantages Data are difficult to

interpret. Coarse resolution

except for SAR.

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Infrared Satellite Imagery These images were obtained with an AVHRR sensor (Advanced

Very High Resolution Radiometer) carried on a NOAA Polar Orbiting Environmental Satellite (POES).

Measures the amount of thermal infrared radiation given off by the surface of the ocean.

The amount of thermal infrared radiation given off by an object is related to its temperature (dying embers give off less radiation than a hot fire and a person gives off even less).

Thus by measuring the amount of radiation given off by the ocean we can calculate its temperature.

Page 9: Surveying ii ajith sir class6

Infrared Satellite Imagery These images were obtained with an AVHRR sensor (Advanced

Very High Resolution Radiometer) carried on a NOAA Polar Orbiting Environmental Satellite (POES).

Measures the amount of thermal infrared radiation given off by the surface of the ocean.

The amount of thermal infrared radiation given off by an object is related to its temperature (dying embers give off less radiation than a hot fire and a person gives off even less).

Thus by measuring the amount of radiation given off by the ocean we can calculate its temperature.

Page 10: Surveying ii ajith sir class6
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Role of space measurements of the earth's topography.

This information has wide applications: in geology (e.g., correlating with plate tectonics effects);

In geophysics (eg., Distribution of is static imbalances); In climatology (e.g., Orographic barriers),In hydrology (e.g., Drainage basin characteristics);In glaciology (e.g., Ice sheet thicknesses); In ecology (e.g., Ecozone disposition); andIn planetology (e.g., Comparative global hypsometry [frequency distribution of elevations]).

High resolution regional coverage (on order of 100 m horizontal and 1 m vertical) is technically achievable even now.

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Remote sensing applications

Agriculture

Mapping crop area

Identifying diseases and crop stress

Estimating crop yield in conjunction

with models

Detecting weeds and illicit crops

pasture management

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Remote sensing applicationsCartography

map revisiongeodesy and photogrammetrymerging other data with remote sensing for map presentationuse of stereo imagery for topographic mappingcompile and update thematic maps of various resources

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Remote sensing applications

Engineering

routing power lines

designing transportation networks

site selection

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Remote sensing applications

Erosion mapping mapping and monitoring eroded areas

predicting potential erosion sites

monitoring land degradation and desertification

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Remote sensing applications

Geology

Identifying lineaments and other structural features

mapping geomorphology and geobotany

mineral and petroleum exploration

analysing landform and drainage

identifying rock types

identifying oil seepage

access planning and base map preparation

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Remote sensing applicationsHydrology

detecting near-surface aquifers for ground water

storage

monitoring irrigation performance and usage

supplement investigations for flood plain

management

monitoring on-farm water storage

mapping current and potential salinity sites

estimating soil moisture and surface temperature

planning engineering constructions and monitoring

their effectiveness

Page 18: Surveying ii ajith sir class6

Remote sensing applications

Meteorology routine atmospheric studies of temperature and weather patterns

mapping cloud cover, patterns, composition and temperature

weather forecasting

flood prediction and monitoring

storm warning and damage assessment

locating and tracking cyclones

monitoring bushfires

mapping snow cover, run-off and melt rate

detecting chemical and/or particulate composition of the atmosphere

climate studies

vertical temperature and humidity profiling

deducing geopotential height and upper level wind velocity

mapping cloud drift winds

Page 19: Surveying ii ajith sir class6

Remote sensing applications

Oceanography

estimating sea surface temperature

ocean colour mapping

mapping of sea surface and sea floor topography

detecting navigational hazards

mapping ocean currents, wind and wave action

detecting oil spills, thermal effluent or other pollution

mapping fish populations and movements

identifying upwelling areas of biological significance

studies of sea ice and glacial movement

Page 20: Surveying ii ajith sir class6

Remote sensing applications

Renewable resources

land cover inventory and monitoring

modeling vegetation structure

detecting land use changes

mapping landform types

mapping potential bushfire status

assessing the impact of natural disasters such

as fire or drought

Page 21: Surveying ii ajith sir class6

Remote sensing applications

Shallow water mapping

bathymetric studies

mapping turbidity and estimating suspended sediment

concentration

mapping chlorophyll content, such as for algal

blooms

mapping reef type and morphology

monitoring sea grass distribution

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Remote sensing applications

Urban studies

mapping extent of, and changes, in urban settlements

studies of housing density and urban drainage

land use planning