2. • 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 laser..
3. 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,
chemical compounds
A narrow laser beam can be used to map physical features
with very high resolution.
5. This animation shows a LIDAR with
a single beam scanned in one axis.
The top image shows the scanning
mechanism
the middle image shows the laser's
path through a basic scene
the bottom image shows the sensor's
output, after conversion from polar to
Cartesian coordinates.
6. What can we measure with lidar?
• Clouds
• Aerosol
• Water vapour
• Minor constituents e.g. ozone, hydrocarbons
• Temperature
Lidars can be used from the ground, aircraft or from space
7. Components used in lidar…
1) Laser
2) Scanner and optics
3) Photodetector and receiver electronics
4) Position and navigation systems
8. Laser
• 600–1000 nm lasers are most common for
non-scientific applications.
• Better target resolution is achieved with
shorter pulses, provided the LIDAR receiver
detectors and electronics have sufficient
bandwidth.
9. Scanners and optics
• 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
10. Photodetector and receiver
electronics
• Two main photodetector technologies are used in
From
atmosphere Receiver
lidars: solid state photodetectors, such as silicon
avalanche photodiodes, or photomultipliers.
• The sensitivity of the receiver is another parameter
that has to be balanced in a LIDAR design.
11. Position and navigation systems
- 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).
12. Applications..
• Agriculture- LIDAR also can be used to help farmers
determine which areas of their fields to apply costly fertilizer
to achieve highest crop yeild. 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,
13. Continued..
• 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
enforcement purposes
14. Advantages of LIDAR technology
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 dependence- 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
photogrammetry.
15. Continued..
6) Higher data density - Up to 167,000 pulses per second.
More than 24 points per m2 can be measured.
n 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
data.
16. Disadvantages
• 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 breaking/turbulent
waves
• Lack of foliage/vegetation penetration
• Precise alignment must be maintained
17. Future scope
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 navigation
data
d) Rendezvous and Docking Aid : sensors providing spacecraft bearing,
distance, and approach velocity
18. Summary
• Lidar technique allows continuous
monitoring of profiles with good height
resolution
• Different scattering mechanisms permit
different kinds of measurement
• New technology offers more compact
sources and development of transportable
and mobile systems
