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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_sensing7/27/2019 Topic 7_lidar w18
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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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