Lecture 1 - App. RS

8/7/2019 Lecture 1 - App. RS

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Intro. Remote SensingIntro. Remote Sensing 11

Lecture 1

Definition and Fundamental Principles

of Remote Sensing

Definitions:

Gathering information from a distance devotedto the observation of the earths land and water

surfaces by means of reflected or emittedelectromagnetic energy;

The measurement oracquisition of informationof some property ofan object or phenomenon,

bya

recording device that is not in physic

alcontact with the object or phenomenon under

study

-Colwell, 1983


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Using sensors other than (or in addition to) a

conventional camer

athrough which scenes

arerecorded using electronic scanning, radiation

outside the normal visual range, radar, thermal,

infrared, ultraviolet and multi-spectral ranges with

special techniques applied to process and

interpretation of images. (American Society ofPhotogrammetry);


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1930-1940 Development of radar in Germany,USA, and UK;

1940-1950 WW II: application of nonvisibleportion of the electromagnetic spectrum; training ofpersons in acquisition and interpretation ofairphotos;

1950-1960 Military research and development

1960-1970 First use of the term remote sensing

TIROS weather satellite; Skylab remote sensingobservations from space;

1972 Launching of Landsat 1 the firstsystematic repetitive observation of the earths landarea;

1970-1980 Rapid advances in digital imageprocessing;

1980-1990 Landsat 4: new generation of Landsatsensors;


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1986 SPOT French Earth observation satellite;

1980s Development of hypospectral sensors;

1990s Global remote sensing;

(Campbell, j. 2002)

GIS and Remote Sensing: Recent

History:

In the past 10-15 years, GIS and RS have matured

as technologies;

Computer power increased many-fold, and

computers penetrated many new work environments

(like geology);

Costs of data storage have fallen dramatically;


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New technological developments have led to

improved sensor resolution (spatial and

spectral);

GUIs (Graphical User Interfaces) have made

software easier (sometimes) to use;

Low-cost desktop GIS/RS software programswere developed;

Development of the Global Positioning System

(GPS);


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Components of Remote

Sensing: An energy source: Sun -

the main energy source;

- Passive systems:

measurement of natural

radiation such as reflected

sunlight;

- Active systems: RS

systems carrying its own

source of electromagneticenergy e.g. radar - not

meteorological dependent


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Propagation medium: The atmosphere throughwhich energy passes

- The ability of the atmosphere to transmit andblock electromagnetic energy is important in

remote sensing accuracy;

Energy detector or sensor: The principalphysical basis for RS is the capacity of sensorinstruments to measure spectral, spatial, andtemporal variation in the energetic bodies;

- Films and detectors developed to measure

electromagnetic energy of various wavelengths

and under various conditions;- The property ofan object measured by the type

of radiation coming from it;


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A Platform: The location of sensors;

-Aircrafts at various heights above the earth;- Spacecraft and satellites in earth orbit; and

- Ground platforms on the earths surface;

Data handling: Analysis and data reduction of

data collected in the form of photographs,imagery, or electrical signals;

- Ground truthing for calibration is a significant

input in data handling;


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KeyConcepts in RS:

Spectraldifferentiation:

RS depends on observing spectral differences in

energy reflected or emitted from objects of

interest;

Based on the principle of multispectral RS;

Spectral signature refers to the response ofa

feature as observed overa range of wave lengths;

Radiometric differentiation:

The dependence on the detection of differences in

brightness of objects and features;


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Recording contrast to derive

information about an object;

Spatialdifferentiation:

Sensors limited in the size of

the smallest area that can be

separately recorded on an

image resolution; Determines spatial detail;

Picture elements (pixels)

smallest area units

identifiable on an image;- Discrete, distinct units

represented by a digital

number;


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Geometric transformation:

Remotely sensed image represents alandscapes in a specific geometric relationship;

Operation condition, topographic relief, type of

instrument factors determining geometric

relationships; Position error resulting from the motion of

scanning, relief, earth curvature, and the

perspective view of the instrument;

- results in geometric error which must be takeninto account before use in measuring areas and

distances;


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Interchangeability of pictorialand digital

formats:

Photogra

phic-like images c

an be represented indigital format by creating pixels and

representing the brightness of these by discrete

values;

Digital images can also be displayed as pictorial

images;

The Atmosphere:

Energy reaching the RS system passes through

the atmosphere;

Particles and gasses in the atmosphere altersthe intensity and wavelength of the suns energy

degrading images or influencing accuracy of

interpretation;


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Remote SensingProcesses:

Problem identification;

Data collection;

Data analysis;

- Analog (visual)Image processing;

- Digital image processing

Preprocessing geometric correction or

rectification, radiometric correction;

Information enhancement im

age reduction,

magnification, transect extraction, principle

component analysis and texture transformation;


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Information extraction using primary

elements of tone and color of imagepixels;

Information Output

Combination with other data to address

specific problems e.g. land-use planning,mineral exploration ect.

Combination with other geospatial data e.g.

GIS soils, geology, transportation network to

guide site location analysis


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Remote Sensing Overview

PhysicalObjects: Buildings, vegetation, soil, water etc.

Sensor data:

Instruments used to view the physical objects

by recording electromagnetic radiation emittedor reflected;

Extracted information:

Transformation of sensor data designed to

reveal specific kinds of information;- Images interpreted to provide information

about soils, land-use, hydrology ect.


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Application: Combining RS with other data to address specific

practical problem


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Why is Remote Sensing Useful?

Large spatial format can give a synoptic view which

is quicker than field reconnaissance with notemporal variations;

Can acquire data from inaccessible regions;

Spectral range of sensors allows for collection ofdata in invisible wavelengths;

Allows for detection of change over time;

In many professions location in geographic spaceis important : (What is the latitude and longitude ofthe forest fire? What is the density of pine trees in

my field area? What is the area ofa riversfloodplain, and are there homes and businessesthreatened by floods?


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GIS and remote sensing are mapping technologies;

that deal with spatial information; The Best Map is an Image (Erdas Imagine

software slogan), and maps based on images;


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Readings:

Remote Sensing and Digital Image

Processing. Lillesand and Kiefer,

1989. Pg. 1-9

Introduction to Remote Sensing. James B.

Campbell. Chapter 1

Documents

Lecture 1 - App. RS