2. CONTENTS:
Introduction
History
Components of LIDAR System
Basic Working Principle
LIDAR Platforms
Types of LIDAR
Applications
Advantages / Disadvantages
Conclusion / References
3. LIDAR:
Acronym for Light Detection And Ranging (sometimes Light Imaging,
Detection, And Ranging).
The LASER system, employed for monitoring the nature of environment is
called LIDAR.
It is an active remote sensing technology that measures distance by
illuminating a target with a laser and analyzing the reflected light.
Similar to RADAR, but uses laser light pulses instead of radio waves.
LIDAR uses ultraviolet rays , visible rays and near infrared rays to image
object.
By illuminating the target using laser beam ,a 3-D point cloud of the target
and it’s surrounding can be generated.
Three types of information can be obtained:
a) Range to target (Topographic LIDAR, or Laser Altimetry)
b) Chemical properties of target (Differential Absorption LIDAR)
c) Velocity of target (Doppler LIDAR)
4. WHY LIDAR ?
It is used for generating precise and directly geo-referenced spatial
information.
Lasers produce a coherent light source.
It is Active sensor , do not require sunlight, they can be used either
during the day or at night.
LIDAR is popularly used as a technology used to make high
resolution maps.
5. HISTORY OF LIDAR:
In the 1930s first attempts were made to measure air density profiles
in the upper atmosphere by determining the scattering intensity
from searchlight beams .
LIDAR originated in the early 1960s, shortly after the invention of
the laser.
combined laser-focused imaging with the ability to calculate
distances by measuring the time for a signal to return using
appropriate sensors and data acquisition electronics.
Its first applications came in meteorology, where the National
Center for Atmospheric Research used it to measure clouds.
The general public became aware of the accuracy and usefulness of
LIDAR systems in 1971 during the Apollo 15 mission, when
astronauts used a laser altimeter to map the surface of the moon.
1995 - First commercial airborne LIDAR systems developed.
6. Components of LIDAR System:
Component of lidar system-LASER :
Frequency: 50,000 (50k) to 200,000 (200k) pulses per second
(Hz) (slower for bathymetry)
Wavelength:
Infrared (1500 – 2000 nm) for meteorology
Near-infrared (1040 - 1060 nm) for terrestrial mapping
Blue-green (500 – 600 nm) for bathymetry
LIDAR Transceiver- Generates laser beam and captures laser
energy scattered/reflected from target.
Scanner- A laser scanner has three sub-components: the opto
mechanical scanner, the ranging unit, and the control processing
unit
7. Components of LIDAR System:
POS(IMU & GPS)- Measures “sensor” position and orientation,
Inertial measurement systems also contain accelerometers to
measure the velocity.
Operator- Permits operator interaction (control/monitor) with
system
Data storage - Captures all AIRBORNE system data required for
generation of x , y , z “target” coordinates.
Computer- Integrates/controls interaction of all of the above.
9. Working Principle:
Laser generates an optical pulse.
Pulse is transmitted , reflected and returned to the receiver.
This return beam/pulse is collected and processed to obtain property
of target.
Receiver accurately measures the travel time.
X,Y,Z coordinates can be computed from
1. Laser range
2. Laser scan angle
3. Absolute location of sensor
12. LIDAR Platforms:
AERIAL/AVIATION(Airborne)
- For highly detailed, local elevation data
- Small area where high density is needed
SATELLITE(space borne)
- covers large areas with less detail
TERRESTRIAL(ground spaced)
13. AERIAL/AVIATION platform:
Used for topographic mapping and engineering application.
It has 3 sub parts:
Laser scanning
Fixed wing platform
Rotary wing platform
14. SATELLITE(space borne):
Mapping of remote areas for scientific purpose.
It has 3 sub parts:
Geostationary
Polar
Sun synchronous
15. TERRESTRIAL(ground spaced):
Produce detailed 3D models of buildings, bridges, streetscapes,
factories and other man-made infrastructure.
It has 3 sub types
Short range
Medium range
Long range
16. Bathymetric Mapping System:
Bathymetry is the study of underwater depth of lake or ocean
floors. In other words, bathymetry is the underwater equivalent to
hypsometry or topography.
It uses blue-green laser that can penetrate water and provide returns
of underwater objects or bottom.
Effective collection of near shore bathymetry.
18. Applications:
Agriculture : Create a Topographical map of the fields and reveals
the slopes and sun exposure of the farm land.
Autonomous vehicles: Autonomous vehicles use LIDAR for
obstacle detection and avoidance to navigate safely through
environments.
Geology and soil science: ICE Sat (Ice, Cloud, and land Elevation
Satellite).
Law enforcement: LIDAR speed guns
Surveying, Transport , wind farm optimization and many more.
Atmospheric Remote Sensing and Meteorology.
19. Present Technical Advancement in LIDAR:
LIDAR speed gun-
A LIDAR speed gun is a device used by the police for speed limit
enforcement which uses LIDAR to detect the speed of a vehicle.
Unlike Radar speed guns, which rely on Doppler shifts to measure
the speed of a vehicle, these devices allow a police officer to
measure the speed of an individual vehicle within a stream of
traffic.
Google driverless car-
Google's robotic cars have about $150,000 in equipment including
a $70,000 LIDAR (light radar) system. The range finder mounted
on the top is a Velodyne 64-beam laser. This laser allows the vehicle
to generate a detailed 3D map of its environment. The car then takes
these generated maps and combines them with high resolution maps
of the world, producing different types of data models that allow it
to drive itself.
21. Advantages / Disadvantages of LIDAR
Higher accuracy
Fast acquisition and processing
Acquisition of 1000 km2 in 12 hours.
DEM generation of 1000 km2 in 24 hours.
Minimum human dependence
As most of the processes are automatic unlike photogrammetric,
GPS or land surveying.
Weather/Light independence
Data collection independent of sun inclination and at night and
slightly bad weather.
Higher data density
Up to 167,000 pulses per second. More than 24 points per Square
meter can be measured.
Multiple returns to collect data in 3D.
22. DISADVANTAGE:
Inability to penetrate very dense canopy leads to elevation model
error.
Ineffective during heavy rain.
High operational cost.
23. Conclusion:
LIDAR mapping is a maturing technology in our country, and
applications are still being identified and developed as end-users
begin to work with the data. There are on-going initiatives to
identify areas where the technology allows value-added products to
be generated or where it offers significant cost reductions over
traditional survey methods.
LIDAR is unobtrusive and environmentally friendly, Unlike ground
survey techniques. Airborne LIDAR can be flown over areas where
access is limited, impossible, or undesirable.
24. References:
[1]K. Thyagarajan and A.K. Ghatak, ‘Laser Theory and Application’
Macmillan Publication.
[2] Dr. M.N. Avadhanulu & Dr. P.S. Hemne, ‘An Introduction to Laser
Theory and Application’, S.CHAND Publication.
[3] IEEE paper, ‘Design concept for a global wind sensing lidar’
DOI: 10.1109/JQE.1979.1070185
[4]Slide-share, ‘Introduction to LIDAR Technology’
https://www.slideshare.net/search/slideshow?searchfrom=header&q
=lidar.
[5]Wikipedia-Introduction to lidar - https://en.wikipedia.org/wiki/Lidar
