LIDAR is a remote sensing method that uses light in the form of a pulsed laser to measure ranges (variable distances) to the Earth. It can be used to generate precise, three-dimensional information about the structure of objects and terrain. LIDAR involves the measurement of distance to a target by illuminating that target with laser light and measuring the reflected pulses with a sensor. Differences in laser return times and wavelengths can then be used to make digital 3D representations of the target. LIDAR originated in the 1960s and has various applications including terrain mapping, atmospheric studies, robotics, autonomous vehicles, archaeology, geology and forestry.
3. SURVEYING METHODS
• SONAR = Sound Navigation and Ranging
• RADAR = Radio Detection and Ranging
• LIDAR = Light Detection and Ranging
4. LIDAR
• Lidar (also called LIDAR, LiDAR, and LADAR) is a surveying method
that measures distance to a target by illuminating that target with a
pulsed laser light, and measuring the reflected pulses with a sensor.
• Differences in laser return times and wavelengths can then be used
to make digital 3-D representations of the target.
5. HISTORY
• Lidar originated in the early 1960s, shortly after the invention of
the laser, and 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 15mission, when astronauts used a laser altimeter
to map the surface of the moon.
6. PRINCIPLE
• LiDAR works in a similar way to Radar and Sonar yet uses light waves
from a laser, instead of radio or sound waves. A LiDAR system
calculates how long it takes for the light to hit an object or surface
and reflect back to the scanner. The distance is then calculated using
the velocity of light. These are known as ‘Time of Flight’
measurements.
11. LASER
• The Lasers are categorized by their wavelength. Airborne Light Detection
and Ranging systems use 1064nm diode-pumped Nd: YAG lasers whereas
Bathymetric systems use 532nm double diode-pumped Nd: YAG lasers
which penetrate into the water with less attenuation than the airborne
system (1064nm). Better resolution can be attained with shorter pulses
provided the receiver detector and electronics have sufficient bandwidth to
manage the increased data flow.
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13. SCANNER AND OPTICS
• The speed at which images can be developed is affected by the speed
at which it can be scanned into the system. A variety of scanning
methods is available for different resolutions such as azimuth and
elevation. dual axis scanner, dual oscillating plane mirrors, and
polygonal mirrors. The type of optic determines the range and
resolution that can be detected by a system.
15. PHOTO DETECTORS
• The photo detector is a device that reads and records the
backscattered signal to the system. There are two main types of
photo detector technologies, solid state detectors, such as silicon
avalanche photodiodes and photomultipliers
16. POSITION AND NAVIGATION SYSTEM
• Lidar sensors that are mounted on mobile platforms such as airplanes
or satellites require instrumentation to determine the absolute
position and orientation of the sensor. Such devices generally include
a Global Positioning System receiver and an Inertial Measurement
Unit(IMU).
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18. PROCESSING STEPS OF 3D LIDAR
IMAGE
1) The image is stored in the point cloud.
2) Import “raw” points into a GIS(Global Information System) format
3) Convert points to a TIN(Triangular Irregular Network) model of the
surface
4) Convert TIN model to a raster model of the surface
Digital Elevation Models (DEM)
Digital Surface Models (DSM)
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20. SOFTWARES USED
• QT Modeler
• TerraScan
• ArcGIS (Workstation, LiDAR Analyst, 3D Analyst, LP360)
• Leica Photogrammetry Suite
21. APPLICATIONS
• Airborne lidar
• Terrestrial lidar
• Agriculture
• Archaeology
• Autonomous vehicles
• Biology and conservation
• Geology and soil science
• Atmospheric remote sensing and
meteorology
• Military
• Mining
• Physics and astronomy
• Rock mechanics
• Robotics
• Spaceflight
• Surveying
• Forestry
• transport
22. AUTOMOTIVE VEHICLES
• TRANSPORTATION: Lidar has been used in adaptive cruise
control (ACC) systems for automobiles. Systems such as those by
Siemens, Hella, and Cepton use a lidar device mounted on the front
of the vehicle, such as the bumper, to monitor the distance between
the vehicle and any vehicle in front of it. In the event the vehicle in
front slows down or is too close, the ACC applies the brakes to slow
the vehicle. When the road ahead is clear, the ACC allows the vehicle
to accelerate to a speed preset by the driver
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25. LIDAR IN ROBOTICS
ROBOTICS:
LIDARs are being used in almost every commercial or industrial mobile
robot in operation or under development today. Once you start looking
for them, you see them everywhere, from simple material-handling
robots to advanced autonomous cars. LIDARs are also used extensively
in applications besides navigation and localization: you can use them to
make detailed 3D scans of areas, for example, or to establish safety
curtains.
27. AEROSPACE
• Lidar has also been used for atmospheric studies from space.
• By precisely timing the lidar 'echo,' and by measuring how much laser
light is received by the telescope, scientists can accurately determine
the location, distribution and nature of the particles. The result is a
revolutionary new tool for studying constituents in the atmosphere,
from cloud droplets to industrial pollutants, that are difficult to detect
by other means
• A ceilometer is a device that uses a laser or other light source to
determine the height of a cloud ceiling or cloud base. Ceilometers can
also be used to measure the aerosol concentration within the
atmosphere.
29. ADVANTAGES
- high level of accuracy
- ability to cover large areas quickly
- quicker turnaround, less labor intensive, and lower costs than the
photogrammetric methods
- can collect data in steep terrain and shadows
- can produce DEM and DSM
30. DISADVANTAGES
• inability to penetrate very dense canopy leads to elevation model
errors
• very large datasets that are difficult to interpret and process
• no international protocols
• cost
-$200 - $300 / sq. mile – 3 meters resolution
- $350 - $450 / sq. mile – 1 meter resolution
• The price of velodyne hl-64 is 8000$(inr= 5,20,000app)
