Lidar (also written LIDAR, LiDAR or LADAR) is a remote sensing technology that measures distance by illuminating a target with a laser and analyzing the reflected light. Although thought by some to be an acronym of Light Detection And Ranging,[1] the term lidar was actually created as a portmanteau of "light" and "radar".[2][3] Lidar is popularly used as a technology to make high-resolution maps, with applications in geodesy, geomatics, archaeology, geography, geology, geomorphology, seismology, forestry, remote sensing, atmospheric physics,[4] airborne laser swath mapping (ALSM), laser altimetry, and contour mapping.
2. 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.
Highly sensitive to aerosols and cloud particles
3. BASIC PRINCIPLE OF LIDAR
In RADAR, radio waves are transmitted into the
atmosphere, which scatters some of the power back to
the Rader’s receiver.
A LIDAR also transmits & receives electro-magnetic
radiation and operate in the ultraviolet, visible and
infrared region of the electromagnetic spectrum. The
LIDAR is also popularly known as LASER RADAR.
A LIDAR basically consists of a transmitter, receiver &
detector
4. LIDAR vs. RADAR
LIDAR uses much shorter wavelength of UV, visible and
near IR range
LIDAR is highly sensitive to non-metallic objects
LIDAR has very narrow beam which produces high
resolution
This makes LIDAR a better choice for studying weather
patterns using small technology, which is especially
useful for studying distant atmospheres through
satellites orbiting around other planets.
5. COMPONENTS
Laser:
600-1000nm lasers used for non-scientific application
1500nm lasers
Scanner
Used to scan the objects , azimuth and elevation
Uses :-
Dual oscillating plane mirror
Dual axis scanner
Optics
They affect angular resolution and range
Photo detector and receiver electronic
Solid state photo detectors
Silicon avalanche photodiodes
Position and navigation systems
6. APPLICATIONS
LIDAR-EQUIPPED MOBILE ROBOT/AGVs
LIDAR-equipped mobile robot uses its LIDAR
to construct a map and avoid obstacles.
(Reference 1)
Driverless car designed for operations on public roads from
Singapore-MIT Alliance for Research and Technology (SMA
(Reference 2)
7. APPLICATIONS PLANETARY BODIES
Used for precision navigation and safe landing
Operational Scenario of Landing Sensors.
Doppler LIDAR prototype system with a fib
coupled optical head having 3 lenses point
to different directions. The Doppler LIDAR
provides vehicle vector velocity and altitu
(Reference 3)
8. APPLICATIONS
METEOROLOGY AND ATMOSPHERIC ENVIRONMENT
Used for studies of atmospherics conditions ,
structures, clouds and aerosols.
Used for measurement of atmospheric gases
Measures wind speed
Used to measure molecular density
FASOR used at the Starfire Optical Range for LIDAR and laser guide star experiments is tuned to th
sodium D2a line and used to excite sodium atoms in the upper atmosphere. (Reference 4)
9. APPLICATIONS
PHYSICS AND ASTRONOMY
Measure the distance to reflectors placed on the moon
Used in Mars-Orbiting Satellite to produce precise
global topographic survey of Mars
Used to detect snow in Mars atmosphere
(NASA Phoenix Lander )
MOLA topographic images of the two hemispheres of Mars (Reference 5)
10. APPLICATIONS
MILITARY AND LAW ENFORCEMENT
Used in traffic speed enforcement for vehicle speed measurement
Uses the principle of time of flight to calculate speed
Able to find the vehicle speed from cluster traffic situation
Higher resolution system collect detail to identify targets (tanks)
TruCAM Laser Speed Gun (Reference 6)
11. APPLICATIONS
ENGINEERING/CONSTRUCTION SURVEY
Using DEM cut and fill quantities can be more precisely estimated
Time delay between data acquisition and delivery is very less
Air bourn LIDAR provide a cost effective and quick surveys for real estate development
LIDAR sample data from NOAA (Reference 7)
12. APPLICATIONS
ENGINEERING/CONSTRUCTION SURVEY
Aerial sensor
Collects/scans data,
eitherphotons
(reflected light) or
laser pulses
Aerial GPS (Global Positioning System)
Based on GPS satellite triangulation, measures the
location
of the aircraft up to 0.1 second.
IMU (Inertial Measurement Unit)
Measures attitude (pitch/yaw/roll) of
aircraft every
.002 second.
Ground GPS
Measures the location of the
aircraft up to 0.1 second
relative to a known ground
position
