Introduction to LiDAR

1. LIDAR
S E M I N A R - 1
Z A I D S H A R I F F – R A 1 7 1 1 0 0 4 0 1 0 2 5 3

2. L I D A R S C A N N E R

3. CONTENTS
• Introduction
• History of LiDAR
• LiDAR Vs RADAR vs SONAR
• General Description
• Basic Architecture of LiDAR
• Measuring with Pixels
• Types of LiDAR
• Applications
• Conclusion

4. INTRODUCTION
What is LiDAR ?
• Light Detection And Ranging
• Remote sensing technology
• Similar to RADAR
• Uses shorter wavelength of the EM-spectrum
• Measures properties of scattered light
• System based on a Laser Sensor

5. HISTORY OF LIDAR
• The first attempts to measure distance by light beams were made in the 1930s
with searchlights that were used to study the structure of the atmosphere.
• In 1938, light pulses were used to determine the heights of clouds.
• After the invention of the laser in 1960, LiDAR was first done using airplanes as the
platform for the laser beam. However, it was not until the arrival of commercially
available Global Positioning System (GPS) equipment and inertial measurement units
(IMUs) in the late 1980s that accurate LiDAR data were possible.

6. LIDAR VS RADAR VS SONAR
LiDAR RADAR SONAR
Uses laser beams Uses Electromagnetic waves Uses sound waves
Measures precise distance
measurements
RADAR measures estimated
distance measurements
Used to detect under water
objects
Measures atmospheric densities
and atmospheric currents
It has a longer operating
distance
It is affected by variations in
sound speed
Used in obtaining 3D images
with high resolution
Cannot detect smaller objects Mostly used to find actual sea
depth
It has a higher measurement
accuracy
No 3D replica of the object It has adverse effects on
marine life
Data can be collected quickly It can operate in cloudy
weather conditions and during
the night
Sonar generates a lot of noise

7. LiDAR rendering of a group
of people. Image courtesy
of NASA.
Weather RADAR imaging
picking up the movement
of weather systems and
migrating birds. Image
courtesy of NASA.
SONAR imaging used to
locate a sunken vessel
at sea. Image courtesy
of the NOAA Office of
Exploration and
Research.

8. GENERAL DESCRIPTION
• LASER - Light Amplification by Stimulated Emission of Radiation.
• Laser + Receiver System=LiDAR
• Monochromatic, Directional, Coherent
• Measure objects that are the same size or larger than its own wavelength.
• Different Performance: on solid surface, on water, on vegetation and for pinpoint
targeting
• LiDAR operates in Ultraviolet, Visible and Infrared region

9. BASIC ARCHITECTURE OF
ARCHITECTURE
Transmitter
Data acquisition and
control system
Receiver
objec
t

10. MEASURING WITH PIXELS
• LiDAR uses a laser to measure distance, but that is not any different from a laser range
finder—you point it at something and you measure a distance. But what if that one
distance measurement were interpreted as a single pixel? You could then take
numerous distance measurements and lay them out in a grid; the result would be an
image that conveys depth, analogous to a black-and-white photograph in which the
pixels convey light intensity. Sounds pretty cool, and that could be pretty useful right?
• But we still have several questions to answer before we can fully understand how this
system works

11. HOW MANY PIXELS DO WE NEED?
• If we compare LiDAR to early digital cameras, we would need one or two megapixels
(or one to two million pixels). So let's say we need two million lasers, then we would
need to measure the distance indicated by every one of those lasers, so another two
million sensors, and then circuits to do the calculations.
• Maybe a whole lot of lasers at once is not the best method. What if, instead of trying
to take a whole "picture" at once, we did what scanners do? Namely, could we take
part of the picture and then move the pixel and take the picture again? This sounds
like a much simpler device that could be implemented with only one laser and one
detector. However, it also means that we cannot take an instant "picture" the way we
can with a camera.

12. HOW DO WE MOVE OUR PIXEL?
• In a scanner, the physical pixel is moved along the image. But that would not be
practical in many situations, so we probably need a different method.
• With LiDAR, we are trying to take a "picture in depth", or you could say we are trying
to take a "3D model".
• If you were paying attention in your math classes, you may recall the Cartesian
coordinate system (X, Y, Z) and the spherical coordinate system (r, theta, phi). I
this up because, if we assume that the LiDAR is at the origin in a spherical system, then
we just need to know the horizontal angle (theta), the vertical angle (phi), and the
distance (r) to build our 3D model.

13. • With only one source, the 3D model would be a
single surface. But if we combine multiple surfaces
mapped together, you can get a full 3D model. So
we need one laser and one sensor to make our
image using the spherical coordinate system.
• Some LiDAR systems are mobile and use GPS or
other positioning systems to map all the readings
together into a single image. These mobile systems
still use the same principles but they may be applied
in different ways.

14. UK 3D mapping
England to be mapped with 3D
LiDAR scanners to tackle flooding
Maya “Megalopolis” Found After
LiDAR Scanning the Guatemalan
Velodyne Lidar

15. TYPES OF LIDAR
• Based on the Platform
• Ground-based LiDAR
• Airborne LiDAR
• Spaceborne LiDAR

16. APPLICATIONS
• LiDAR is used in everything from agriculture to meteorology, biology to robotics, and
law enforcement to solar photovoltaics deployment.
• You might see LiDAR referenced in reports about astronomy and spaceflight or you
might hear about its use in mining operations.
• LiDAR can image small things like historic relics for archaeology or skeletons for
biology. On the other end of the spectrum, LiDAR can also image very large things like
landscapes for agriculture and geology.
Aerial photography - LiDAR

17. • Oceanography
• The LiDAR is used for calculation of phytoplankton fluorescence and
biomass in the ocean surface. It is also used to measure the depth of the
ocean (bathymetry).
• Military
• LiDAR has always been used by the military people to understand the
border surrounding land. It creates a high-resolution map for the military
purpose.
• Meteorology
• LiDAR has been used for the study of the cloud and its behavior. LiDAR
its wavelength to strike small particles in the cloud to understand cloud
density.
• River Survey
• Greenlight (532 nm) Laser of the LiDAR is used to measure underwater
information required to understand the depth, width of the river, flow
strength and more. For the river engineering, its cross-section data are
extracted from Light Detection And Ranging data (DEM) to create a river
model, which will create a flood fringe map.
River Survey Using
LiDAR

18. • Autonomous vehicles use LiDAR for obstacle detection and avoidance to navigate
safely through environments, using rotating laser beams.
• Fusion of 3-D LiDAR and color camera for multiple object detection and tracking -
the data from the camera and 3-D LiDAR is input into the system. Both inputs from
LiDAR and camera are parallelly obtained and the color image from the camera is
calibrated with the LiDAR.

19. CONCLUSION
• Recent development of Structure From Motion (SFM) technologies allows delivering 3-
D images and maps based on data extracted from visual and IR photography merged
with LiDAR. The elevation or 3-D data is extracted using multiple parallel passes over
mapped area, yielding both visual light images and 3-D structure from the same
sensor, which is often a specially chosen and calibrated digital camera.
• Whatever advances occur over the next several years, LIDAR technology will continue
to play a critical role in the autonomous vehicle evolution. As an essential element to
the highly-sophisticated sensor suite in autonomous vehicle, it will facilitate the
autonomous vehicle ability to adapt under a variety of circumstances on the quest to
perform at human driver levels.

20. REFERENCES
• Light Detection and Ranging SONU SANGAM USN-1CR07EC096 Department of
Electronics and Communication Engineering CMR Institute of Technology No.
132,AECS Layout, Bangalore-560 037.
• Research on the technology of LIDAR data processing. Publisher: IEEE Dekui Lv The
28th Research Institute of China Electronics Technology Group Corporation.