Lidar is an acronym for light detection and ranging. It is an optical remote sensing technology that can measure the distance to, or other properties of a target by illuminating the target with light, often using pulses from a laser.
• General Description
• Brief History.
• Lidar Platforms.
• Basic Principle and Technique.
• How Lidar works.
• Lidar components
Lidar is an acronym for light
detection and ranging. It is an
optical remote sensing technology
that can measure the distance to, or
other properties of a target by
illuminating the target with light,
often using pulses from a laser.
Mobile Lidar at UNG
4. General description:
This is an active remote sensing technique , similar to radar
but uses laser light pulses instead of radio waves.
Most lidar systems operate in near infra–red region of
electromagnetic spectrum (i.e , 1064 nm).
Lidar instruments can rapidly measure the earth’s surface at
a sampling rate greater than 150khz.The resulting product is
a densely spaced network of highly accurate georefernced
elevation points –point cloud. It can be used to generate 3-
D representation of earth’s surface.
5. Brief History:
Searchlights were used to measure the altitude of the
clouds. Measurement was done by pointing a beam of
light in sky and then reading the angle at which the
beam of light struck the cloud, on a device that was
known distance away from the searchlight. One was then
able to obtain height by triangulation.
First laser based device was constructed by G.fiocco at
MIT using a ruby laser. From there,the development of
lidar was sky rocketed. Searchlight
7. Basic Principle And Technique:-
The basic idea is fairly straightforward.
Laser generates an optical pulse
Pulse is reflected off an object and returns to
the system receiver.
High-speed counter measures the time of flight
from the start pulse to the return pulse
Time measurement is converted to a distance
(the distance to the target and the position of
the airplane is then used to determine the
elevation and location).
8. How Lidar Works:
I. Directing a laser into
II. Use of telescope.
III. Digitalization of lidar
9. LASER SCANNER AND OPTICS
LIDAR SENSOR AND
PHOTODETECTORS. POSITION AND NAVIGATION SYSTEMS.
Airborne lidar systems
use 1064nm diode
pumped YAG lasers
while bathymetric system
use 532nm double diode
pumped YAG lasers.
Airborne YAG Laser
11. Lidar 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.
Moreover, optic choice effects
the angular resolution and range
that can be detected.
12. Lidar Sensors and Photodetectors:
• The HDL-64E Lidar sensor (shown here)
is designed for obstacle detection and
navigation of autonomous ground vehicles
and marine vessels. Its durability, 360 field
view and very high data rate makes this
sensor ideal for 3D mobile data collection
and mapping applications.
• Two main photodetector technologies are
used in lidars:-Solid State photodetectors
such as silicon avalache photodiodes and
HDL-64E Lidar Sensor
13. Position And Navigation System:
When a Lidar sensor is
mounted on a mobile
platform such as airplanes or
automobiles ,it is necessary to
determine the absolute
position and orientation of
the sensor to retain useable
data . For this, we have two
1)Inability to penetrate very dense canopy leads to elevation model
2)Very large datasets that are difficult to interpret and process.
3)No International Protocols.
4) Precise alignment is required.
Lidar has become an established method for collecting very dense
and elevation data across landscapes, shallow-water areas and
project sites. Moreover, LIDAR can provide high degree of
accuracy and more detailed information about the landscape than
radar technologies .
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