WHAT IS LIDAR ? ?
LIDAR (Light Detection And Ranging also
LADAR) 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
The term "laser radar" is sometimes used, even though,
LIDAR does not employ microwaves or radio waves and
therefore is not radar in the strict sense of the word.
LIDAR uses ultraviolet, visible, or infrared light to
image objects and can be used with a wide range of
targets, including non-metallic objects, rocks, rain,
A narrow laser beam can be used to map physical features
with very high resolution.
Distance to clouds
This animation shows a LIDAR
with a single beam scanned in
The top image shows the
The middle image shows the
laser's path through a basic
The bottom image shows the
sensor's output, after
conversion from polar to
What can we measure with lidar?
• Water Vapour
• Minor constituents e. g. ozone, hydrocarbons
Lidars can be used from the ground, aircraft or from
2) Scanner and optics
3)Photo detector and receiver electronics
4)Position and navigation systems
Components used in lidar...
• 600-1000 nm lasers are most common for
• Better target resolution is achieved with
shorter pulses, provided the LIDAR receiver detectors
and electronics have sufficient bandwidth.
• How fast images can be developed is also 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
Scanners and optics
• Two main photo detector technologies are used in
Lidars: solid state photo detectors, such as silicon
avalanche photodiodes, or photomultipliers.
• The sensitivity of the receiver is another parameter
that has to be balanced in a LIDAR design.
Photodetector and Receiver
• LIDAR sensors that are mounted on mobile
platforms such as airplanes or satellites
require instrumentation to determine the
absolute position and orientation of the
• Such devices generally include a Global
Positioning System receiver and an Inertial
Measurement Unit (IMU).
Position and navigation systems
• Agriculture - LIDAR also can be used to help farmers
determine which areas of their fields to apply costly fertilizer
to achieve highest crop yield. LIDAR can create a
topographical map of the fields and reveals the slopes and
sun exposure of the farm land.
• Biology and conservation- LIDAR has also found many
applications in forestry, Canopy heights, biomass
measurements, and leaf area can all be studied using LIDAR
systems. Similarly, LIDAR is also used by many industries,
Including Energy and Railroad, and the Department of
Transportation as a faster way of surveying. Topographic
maps can also be generated readily from LIDAR.
• Wind farm Optimization-Lidar can be used to
increase the energy output from wind farms by accurately
measuring wind speeds and wind turbulence.
An experimental lidar is mounted on a wind turbine rotor
to measure oncoming horizontal winds, and proactively adjust
blades to protect components and increase power.
• Law enforcement- LIDAR speed guns are used by the
police to measure the speed of vehicles for speed limit
The other methods of topographic data collection are land:
surveying, GPS, inteferrometry, and photogrammetry.LIDAR
technology has some advantages in comparison to these
methods,which are being listed below:
1) Higher accuracy
2) Fast acquisition and processing
3) Minimum human depe11dence- As most of the processes are
automatic unlike photogrammetry, GPS or land surveying.
4) Weather/Light independence- Data collection independent
of sun inclination and at night and slightly bad weather.
5) Canopy penetration-LIDAR pulses can reach beneath the
canopy thus generating measurements of points there unlike
Advantages of LIDAR technology
6) Higher data density - Up to 167,000 pulses per second
More than 24 points per m2 can be measured.
and Multiple returns to collect data in 3D.
7) Cost - Is has been found by comparative studies
that LIDAR data is cheaper in many applications. This is
particularly considering the speed, accuracy and density of
• High operating costs (> £10k / hour)
• Ineffective during heavy rain and/or low cloud/mist
• Degraded at high Sun angles and reflections
• Latency data not processed locally
• Unreliable for water depth (< 2m) and
• Lack of foliage/vegetation penetration
• Precise alignment must be maintained
The lidar technology is now planned for a wide range of applications
that can enable NASA’s achievement of its scientiﬁc and space
exploration goals. These applications fall into four general categories:
a) Earth Science: long-duration orbiting instruments providing global
monitoring of the atmosphere and land
b) Planetary Science: orbiting or land-based scientiﬁc instruments
providing geological and atmospheric data of solar system bodies
c) Landing Aid: sensors providing hazard avoidance, guidance and
d) Rendezvous and Docking Aid : sensors providing spacecraft bearing,
distance, and approach velocity.
• Lidar technique allows continuous
monitoring of profiles with good height
• Different scattering mechanisms permit
different kinds of measurement.
• New technology offers more compact
sources and development of transportable
and mobile systems.