Light detection and ranging (LiDAR) is a remote sensing method that uses pulsed laser light to image objects and measure distances. It can be used for applications such as autonomous vehicles, forest planning and management, river surveying, and oil and gas exploration. The document discusses the history, principles, components, types, concepts and applications of LiDAR technology.
2. TREY
research
AboutUs
2
Applied Electronics
GroupMembers
Shlok Doshi (GL)
Prathamesh Durgule
Aditya Chandanshive
Divyesh Burande
GR.No- 11910482
GR.No- 11910723
GR.No- 11910312
GR.No- 11910926
Guided by:
Prof. Shlipa M Lambor
Department : Instrumentation and Control Engineering
Division : A
Batch : B2
3. TREY
research
Outline
Light detection and ranging (LiDAR)
Introduction
History
General Description
Principle
Architecture
Components
Types
Concepts
Working
Applications
Advantages
Limitations
Future Developments
3
Applied Electronics
4. TREY
research
Introduction
4
Light detection and ranging (LiDAR)
• Lidar is a method for measuring distances (ranging) by illuminating the target
with laser light and measuring the reflection with a sensor.
• It has terrestrial, airborne, and mobile applications.
• Lidar is commonly used to make high-resolution maps, with applications in
surveying, geodesy, geomatics etc.
Applied Electronics
5. TREY
research
History
5
Light detection and ranging (LiDAR)
• Lidar's first applications came in meteorology, where the National Center for
Atmospheric Research used it to measure clouds and pollution.
• The general public became aware of the accuracy and usefulness of lidar systems in
1971 during the Apollo 15 mission.
• In mid-1980s, the lack of reliable commercial global positioning system/inertial
measurement unit (GPS/IMU) solutions for sensor positioning presented
bottlenecks for further development.
• By the mid-1990s, manufacturers of laser scanners were delivering LiDAR sensors
that were capable of 2,000 to 25,000 pulses per second to customers who intended
to use them for topographic mapping applications.
• The scientific uses of LiDAR have continued to evolve.
Applied Electronics
6. TREY
research
Generaldescription
6
• Lidar uses ultraviolet, visible, or near infrared light to image objects.
• It can target a wide range of materials, including non-metallic objects, rocks,
rain, chemical compounds, aerosols, clouds and even single molecules.
• A narrow laser beam can map physical features with very high resolutions.
Light detection and ranging (LiDAR)
Applied Electronics
7. TREY
research
7
Applied Electronics
BasicPrinciple
Light detection and ranging (LiDAR)
• The Lidar instrument fires rapid pulses of laser light at a surface,
some at up to 150,000 pulses per second.
• A sensor on the instrument measures the amount of time it
takes for each pulse to bounce back.
• Light moves at a constant and known speed so the Lidar
instrument can calculate the distance between itself and the
target with high accuracy.
• By repeating this in quick succession the instrument builds up a
complex 'map' of the surface it is measuring.
Fig 1.1 Principle of range
measurement using laser.
9. TREY
research
9
Applied Electronics
Components
Light detection and ranging (LiDAR)
Lasers
• Lasers are categorized by their wavelength.
• 600-1000nm lasers are more commonly used for non-
scientific purposes.
• Lasers with a wavelength of 1550nm are used for longer
range and lower accuracy purposes.
Scanners and Optics
• Image development speed is affected by the speed at which
they are scanned.
• Optic choices affect the angular resolution and range that
can be detected.
• A hole mirror or a beam splitter are options to collect a
return signal.
10. TREY
research
10
Applied Electronics
Components
Light detection and ranging (LiDAR)
Photodetector and Receiver Electronics
• The photodetector is the device that reads and records
the signal being returned to the system.
• There are two main types of photodetector technologies,
solid state detectors, such as silicon avalanche photodiodes
and photomultipliers.
Navigation and positioning systems
• it is necessary to determine the absolute position and
the orientation of the Lidar sensor to retain useable data.
• Global Positioning Systems provide accurate geographical
information regarding the position of the sensor.
• Inertial Measurement Unit (IMU) records the precise
orientation of the sensor at that location.
• These two devices provide the method for translating sensor
data into static points for use in a variety of systems.
11. TREY
research
11
Applied Electronics
Global Positioning System
• Global positioning system, gives the location of the
instrument that's holding the LIDAR sensor.
• GPS-lidar fusion technique implements method for
efficiently modeling lidar-based position error covariance
based on features in the point cloud.
Inertial Measurement Unit
• An IMU is used to determine the attitude of the aircraft as
the sensor is taking measurements.
• These are recorded in degrees to an extremely high accuracy
in all three dimensions.
• The laser beam's exit geometry is calculated relative to the
Earth's surface coordinates to a very high accuracy.
ComponentsEmphasized
Light detection and ranging (LiDAR)
12. TREY
research
12
Applied Electronics
Based on orientation:
• Lidar can be oriented to nadir, zenith and lateral.
• For example, lidar altimeters look down, an atmospheric
lidar looks up etc.
Based on Illumination Method:
Flash LiDAR:
• In flash lidar, the entire field of view is illuminated with a
wide diverging laser beam in a single pulse.
Scanning LiDAR:
• Light is sequentially emitted in each direction and the
corresponding echoes are detected one by one by the
detector.
Types
Light detection and ranging (LiDAR)
13. TREY
research
13
Applied Electronics
Based on platform:
Types
Light detection and ranging (LiDAR)
Terrestrial
• Terrestrial applications of lidar happen on the Earth's
surface and can be either stationary or mobile.
• Stationary terrestrial scanning is most common as a survey
method, for example in conventional topography,
monitoring, cultural heritage documentation and forensics.
Airborne
• Airborne lidar is when a laser scanner, while attached to an
aircraft during flight, creates a 3-D point cloud model of the
landscape.
• This is currently the most detailed and accurate method of
creating digital elevation models, replacing photogrammetry.
Airborne Bathymetric
• Bathymetric LIDAR systems have been specifically developed
to measure water depth.
14. TREY
research
14
Applied Electronics
Airborne
Light detection and ranging (LiDAR)
• The airborne Topographical LiDAR system is comprised of three
major time-synchronized components: a laser scanner unit, a
GPS, and an IMU.
• The laser scanner is composed of a laser range finder unit, which
is based on time-of-flight distance measurement techniques, and
a beam deflection device that creates the desired scanning
pattern.
• The GPS provides the absolute position of the sensor platform
(plat), and the IMU records the angular attitude of the platform
• This enables the system to generate the aircraft's absolute
position (X, Y, Z) at any given time.
Fig 4.1 working of Airborne LiDAR.
16. TREY
research
16
Applied Electronics
Bathymetric
Light detection and ranging (LiDAR)
• The airborne bathymetric lidar technological system involves the
measurement of time of flight of a signal from a source to its
return to the sensor.
• It works using a green spectrum (532 nm) laser beam.
• Two beams are projected onto a fast-rotating mirror, which
creates an array of points.
• One of the beams penetrates the water and detects the bottom
surface of the water under favorable conditions.
• The data obtained shows the full extent of the land surface
exposed above the sea floor.
• This technique is extremely useful as it will play an important role
in the major sea floor mapping program.
Fig 4.3 Portion of the seafloor taken using
bathymetric LiDAR
17. TREY
research
17
Applied Electronics
Bathymetric
Light detection and ranging (LiDAR)
Fig 4.4 High-resolution multibeam lidar map showing spectacularly faulted and deformed
seafloor geology, in shaded relief and colored by depth. NOAA Ocean Exploration &
Research.
18. TREY
research
18
Applied Electronics
Ground-based
Light detection and ranging (LiDAR)
• Ground-based Lidar systems are very similar, only that an IMU
is not required.
• the Lidar is usually mounted on a tripod which the Lidar
sensor rotates 360 degrees around.
• The pulsed laser beam is reflected from objects such as
building fronts, lamp posts, vegetation, cars and even people.
• The return pulses are recorded and the distance between the
sensor and the object is calculated.
• The data produced is in a 'point cloud' format, which is a 3-
dimensional array of points, each having x, y and z positions
relative to a chosen coordinate system.
Fig 4.5 Diagram of the instrument’s scanning
pattern.
19. TREY
research
19
Applied Electronics
Ground-based
Light detection and ranging (LiDAR)
Fig 4.6 A ground based lidar system is used to analyze and scan the ancient desert city of
Petra in the National Geographic program "Time Scanners" Image Credit: National
Geographic.
20. TREY
research
20
Applied Electronics
Point Clouds
• Collection of points that represent a 3D shape or feature.
• Each point has its own set of X, Y and Z coordinates and in some
cases additional attributes.
• When many points are brought together, they start to show some
interesting qualities of the feature that they represent.
• Most often created by methods used in photogrammetry or remote
sensing.
• The point clouds are saved as .las files for further developments.
Concepts
Light detection and ranging (LiDAR)
Fig 2.1 Point Cloud
mapping of a Terrain.
21. TREY
research
21
Applied Electronics
Laser Returns
• Laser pulses emitted from a lidar system reflect from objects both on and above the ground surface: vegetation, buildings,
bridges, and so on.
• Any emitted laser pulse that encounters multiple reflection surfaces as it travels toward the ground is split into as many returns
as there are reflective surfaces.
• The first returned laser pulse is the most significant return and will be associated with the highest feature in the landscape like
a treetop or the top of a building.
Concepts
Light detection and ranging (LiDAR)
22. TREY
research
22
Applied Electronics
Laser Returns
• Multiple returns can detect the elevations of
several objects within the laser footprint of an
outgoing laser pulse.
• The intermediate returns, in general, are used
for vegetation structure, and the last return for
bare-earth terrain models.
Fig 2.2 pulse hitting a thick branch on its way to the ground.
23. TREY
research
Applications
23
Light detection and ranging (LiDAR)
• Autonomous Vehicles
• Forest Planning and Management
• Forest Fire Management
• River Survey
• Oil and Gas Exploration
Applied Electronics
24. TREY
research
24
Applied Electronics
Autonomous Vehicles
Light detection and ranging (LiDAR)
• Autonomous vehicles may use lidar for obstacle detection and
avoidance to navigate safely through environments.
• Point cloud output from the lidar sensor provides the necessary
data for robot software.
• Software determine where potential obstacles exist in the
environment and where the robot is in relation to those potential
obstacles.
• Examples of companies that produce lidar sensors commonly
used in vehicle automation are Ouster and Velodyne.
Fig 4.7 Cruise Automation self-driving car
with five Velodyne LiDAR units on the roof.
"There is absolutely a movement afoot to add LIDAR to
mainstream automotive vehicles, which is something that
you would buy off of a dealership,”
-Anand Gopalan, CEO of Velodyne.
25. TREY
research
25
Applied Electronics
Autonomous Vehicles-Working
Light detection and ranging (LiDAR)
• Continuously rotating LiDAR system sends thousands of laser
pulses every second.
• These pulses collide with the surrounding objects and reflect.
• The resulting light reflections are then used to create a 3D point
cloud.
• An onboard computer records each laser’s reflection point and
translates this rapidly updating point cloud into an animated 3D
representation.
• 3D representation is created by measuring the speed of light and
the distance covered by it.
• It helps to determine the vehicle’s position with other
surrounding objects.
• It helps to command the brakes to slow or stop the vehicle.
• When the road ahead is clear, it also allows the vehicle to speed
up.
27. TREY
research
27
Applied Electronics
Forest Planning and Management
Light detection and ranging (LiDAR)
• Lidar is widely used in the forest industry to plan and manage.
• It is used to measure vertical structure of forest canopy and also
used to measure and understand canopy bulk density and
canopy base height.
• Also used for the measurement of the peak height.
• To estimate the root expansion.
Fig 4.9 Airborne LiDAR Drone scanning
Forest floor.
29. TREY
research
29
Applied Electronics
Forest Planning and Management
Light detection and ranging (LiDAR)
Case-Study
• Carried out In the Mediterranean coniferous stand of western Greece, located near Gouria, Aetolia-Acarnania village of Greece.
• Terrestrial LiDAR was used to measure the DBH(Diameter Breast Height) of trees and tree height.
• Using the dense 3D reconstruction, fitting algorithms to automatically compute the Diameter at Breast Height (DBH) at 1.3 meters
from the base of the tree.
• For the measurement of the tree height, first, the individual tree was segmented from the TLS derived point cloud.
• Then, the individual tree was measured using the difference between the two ends of the point cloud.
32. TREY
research
32
Applied Electronics
Forest Planning and Management
Light detection and ranging (LiDAR)
Case-Study
• The results were validated using the field measurements of the DBH and Tree Height using a tree caliper held at right angles to
the tree trunk at 1.3 m from the base of the tree.
• Finally, this research concludes that TLS is highly potential in deriving forest inventory variables (DBH and tree height) and
structural characteristics like volume in greater accuracy.
• The results confirm that Terrestrial LiDAR can provide a non-destructive, high-resolution and precise determination of forest
inventory parameters.
• The outcomes will help researchers to better comprehend deviations in the accuracy of forest inventory variable.
• The outcomes will additionally boost decision-making in forest management.
33. TREY
research
33
Applied Electronics
Forest Fire Management
Light detection and ranging (LiDAR)
• Lidar is becoming widely popular in forest fire
management.
• Fire department is transforming from reactive to
proactive fire management.
• Lidar image helps to monitor the possible fire area which is
called fuel mapping (fire behavior model).
Fig 4.14 LiDAR for forest fire study.
34. TREY
research
34
Applied Electronics
River Survey
Light detection and ranging (LiDAR)
• Underwater information is required to understand depth, flow
strength, width of the river and more.
• For the river engineering, its cross-section data is extracted from
Lidar data (DEM)to create a river model, which will create
flood and flood fringe map.
• Lidar is used to create high resolution and accurate surface
model of the river.
• These extracted Lidar information can be used for the 3D
simulation for better planning of the structures or buildings on
the riverbank.
Fig 4.15 Depth map of river using
LiDAR.
35. TREY
research
35
Applied Electronics
Oil and Gas Exploration
Light detection and ranging (LiDAR)
• As Lidar wavelengths are shorter, it can be used to detect
molecules content in the atmosphere that has same or bigger
wavelength
• There is the new technology called DIAL (Differential
Absorption LiDAR) which is used to trace amount of gases
above the hydrocarbon region.
• This tracking helps to find the Oil and Gas deposits.
Fig 4.16 An alteration mineral map.
36. TREY
research
Advantages
36
Light detection and ranging (LiDAR)
Resolution & Accuracy:
LiDAR generates instantaneous, massive amounts of measurements, and can
be accurate to a centimeter.
Applied Electronics
Low Light Performance:
LiDAR is unaffected by ambient light variations and performs well in low any
light conditions.
37. TREY
research
Advantages
37
Light detection and ranging (LiDAR)
3D Mapping:
LiDAR data can be easily converted into 3D maps to interpret the
environment
Applied Electronics
Speed:
LiDAR data are direct distance measurements that don’t need to be
deciphered or interpreted– thus enabling faster performance and reducing
processing requirement.
38. TREY
research
Limitations
38
Light detection and ranging (LiDAR)
• It can’t see beyond solid objects.
• This is true for any system that relies on a signal travelling in a straight line.
• If the unit is obscured by anything in close range, a lot of data is lost.
• Adverse weather conditions or clashing signals from another LiDAR unit could
also interfere with the infrared signals.
Applied Electronics
39. TREY
research
FutureDevelopments
39
Shrinking LiDAR
• LIDAR needs to be much smaller to see widespread use.
• In order to accomplish that, Voyant Photonics is ditching the mechanical movement altogether.
• They use silicon photonics to sweep the laser without using mechanical parts at all.
• Silicon photonics is the study and use of light in silicon.
• It’s still a relatively new field, and most research is going into the use light on chips in place of
conventional electrical connections.
• In this case, Voyant Photonics is using silicon photonics “optical phased arrays” to direct the
laser beam across the scene without moving parts.
• The result is a LIDAR chip that is in orders of magnitude smaller than existing modules.
Applied Electronics
42. TREY
research
References
42
Applied Electronics
• Airborne laser scanning: basic relations and formulas, E.P. Baltsavias , ISPRS Journal of Photogrammetry & Remote Sensing 54
1999 199–214.
• A Guide to LIDAR Data Acquisition and Processing for the Forests of the Pacific Northwest, Demetrios Gatziolis and Hans-Erik
Andersen, Pacific Northwest Research Station, General Technical Report,PNW-GTR-768 July 2008.
• Lidar Systems and Data Processing Techniques,Mark Hansen and Peter Howd.
