topic 7_lidar w18

7/27/2019 Topic 7_lidar w18

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TOPIC 7 :

LIDAR

PHOTOGRAMMETRY 2:

CG504

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LIDAR

PURPOSE :

7.1 UNDERSTAND THE CONCEPT OF LIDAR

MAPPING

CONTENTS :

7.1.1 State the principle of LIDAR mapping

7.1.2 Describe LIDAR :a) operation system

b) application

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THE CONCEPT OF LIDAR MAPPING

LIDAR is Light Detection And Ranging

LIDAR (Light Detection And Ranging, also LADAR) is anoptical remote sensing technology that can measure

the distance to, or other properties of a target byilluminating the target with light, often using pulsesfrom a laser. LIDAR technology has applicationin geomatics, archaeology, geography, geology, geomorphology,seismology, forestry, remotesensing and atmospheric physics,[1] as well as inairborne laser swath mapping (ALSM), laser altimetryand LIDAR contour mapping.

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http://en.wikipedia.org/wiki/Remote_sensinghttp://en.wikipedia.org/wiki/Lighthttp://en.wikipedia.org/wiki/Laserhttp://en.wikipedia.org/wiki/Lighthttp://en.wikipedia.org/wiki/Geomaticshttp://en.wikipedia.org/wiki/Geomaticshttp://en.wikipedia.org/wiki/Geomaticshttp://en.wikipedia.org/wiki/Archaeologyhttp://en.wikipedia.org/wiki/Geographyhttp://en.wikipedia.org/wiki/Geologyhttp://en.wikipedia.org/wiki/Geomorphologyhttp://en.wikipedia.org/wiki/Geomorphologyhttp://en.wikipedia.org/wiki/Seismologyhttp://en.wikipedia.org/wiki/Seismologyhttp://en.wikipedia.org/wiki/Seismologyhttp://en.wikipedia.org/wiki/Archaeologyhttp://en.wikipedia.org/wiki/Forestryhttp://en.wikipedia.org/wiki/Forestryhttp://en.wikipedia.org/wiki/Forestryhttp://en.wikipedia.org/wiki/Geographyhttp://en.wikipedia.org/wiki/Remote_sensinghttp://en.wikipedia.org/wiki/Geologyhttp://en.wikipedia.org/wiki/Geomorphologyhttp://en.wikipedia.org/wiki/Remote_sensinghttp://en.wikipedia.org/wiki/Seismologyhttp://en.wikipedia.org/wiki/Atmospheric_physicshttp://en.wikipedia.org/wiki/Atmospheric_physicshttp://en.wikipedia.org/wiki/Atmospheric_physicshttp://en.wikipedia.org/wiki/Atmospheric_physicshttp://en.wikipedia.org/wiki/Atmospheric_physicshttp://en.wikipedia.org/wiki/Remote_sensinghttp://en.wikipedia.org/wiki/Remote_sensinghttp://en.wikipedia.org/wiki/Atmospheric_physicshttp://en.wikipedia.org/wiki/LIDARhttp://en.wikipedia.org/wiki/Contour_maphttp://en.wikipedia.org/wiki/Contour_maphttp://en.wikipedia.org/wiki/Contour_maphttp://en.wikipedia.org/wiki/LIDARhttp://en.wikipedia.org/wiki/Atmospheric_physicshttp://en.wikipedia.org/wiki/Remote_sensinghttp://en.wikipedia.org/wiki/Remote_sensinghttp://en.wikipedia.org/wiki/Forestryhttp://en.wikipedia.org/wiki/Seismologyhttp://en.wikipedia.org/wiki/Geomorphologyhttp://en.wikipedia.org/wiki/Geomorphologyhttp://en.wikipedia.org/wiki/Geologyhttp://en.wikipedia.org/wiki/Geographyhttp://en.wikipedia.org/wiki/Archaeologyhttp://en.wikipedia.org/wiki/Geomaticshttp://en.wikipedia.org/wiki/Laserhttp://en.wikipedia.org/wiki/Lighthttp://en.wikipedia.org/wiki/Remote_sensing


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THE PRINCIPLE OF LIDAR

MAPPING

LIDAR is a relatively new technological tool

that can be used to accurately georeference

terrain featuresA LIDAR system is composed of a laser

scanning system, global positioning system

(GPS), and an inertial measuring unit (IMU).Laser is fired at the ground from an airplane

to measure distance to the ground

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THE PRINCIPLE OF LIDAR

MAPPING

By reclecting from objects, the LIDAR pulse

finds the edges of and gaps & holes in

objects and reaches the ground.

The LIDAR returns are reflected back to the

aircraft-mounted sensor where they create an

accurate and valuable dataset.

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OPERATION SYSTEM

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Different between Pulsedand CW Lidar systems.

Pulsed system : Transmitted signal consists of aseries of laser pulses, 10,000 to 150,000pulses/second (10 - 150 kHz pulse rate). Range to

target calculated from time to receive pulse :Range = c*t / 2.

CW system : Transmits sinusoidal signal of knownwavelength Range calculated from number of full

waveforms and the phase difference betweentransmitted and received signal. Much lesscommon technique compared to pulsed system.

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ADVANTAGES LIDAR Fast and cost-effective mapping over large areas

reduce time and cost.

High accuracy: Vertical: 0.15m or better and

Horizontal: 0.20m or better. High density points: 1-40 point/m2 or more.

Data can be collected at night

Penetrate canopy.

Intensity image supports terrain featureclassification.

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DISADVANTAGES LIDAR No pictorial record

Need GPS base stations

Huge datasets

Smaller projects may be more expensive than

traditional photogrammetry due to

mobilization costs.

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Pulsed System OperationWavelengths utilized:

1.0 - 1.5 m(terrestrial studies) 0.50 - 0.55 m

Combination of scanning mirror and moving

platformproduces a 2D field of range measurements

Additionally recorded information :

Angle from nadir of measurement

GPS horizontal and vertical positions ( 1 Hz)

Aircraft Inertial Measurements (pitch, roll, yaw) (50 Hz)

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Pulsed System OperationOn board processing :

Slant distance calculated from range measurement +

angle from nadir for each returned pulse Slant distance corrected using IMU measurements

GPS data integrated to provide a georeferencedelevation value for each returned pulse.

GPS measurements are crucial to vertical accuracy.

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APPLICATION

Forestry Management and Planning

ability to measure the vertical structure of

forest canopies

able to predict canopy bulk density and

canopy base height

LiDAR surveys allow large scale surveys to be

taken with a level of cost-effectiveness not

previously available.

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APPLICATION

Flood Modelling

Only high-resolution input data can solve the

purpose that relates to the systems

topography

LiDAR has brought this level of detail to the

industry allowing for much more accurate

flood prediction models to be created.

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APPLICATION

Pollution Modelling

LiDAR has a unique ability to detect particles

in both water and air.

LiDAR uses short wavelengths of light in the

visible spectrum, typically ultraviolet, visible

or near infrared

This makes it particularly sensitive to aerosols,

cloud particles and air molecules

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APPLICATION

Mapping and Cartography

high resolution and accuracy has enabled it to

be used in the creation of maps.

LiDAR can assist in road, building and

vegetation mapping.

3D aspect of LiDAR makes it especially suitable

for mapping terrain models, including complex

mountain topography

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APPLICATION

Urban Planning

LiDAR data is a relatively new technology for

obtaining Digital Surface Models (DSMs) of

the earth's surface.

when combined with digital orthophotos, can

be used to create highly detailed DSMs

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LESSON LEARNING OUTCOME (CLO) :

Upon completing this topic, the students should be able

to:

1. Describe principles of LIDAR mapping, systemoperation and application

Finally, lets review all the topics that wehave covered

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Thank

you

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