LiDAR is a remote
sensing technology which is used to measure elevation of objects from a
specified level. This technology uses laser to detect the objects. LiDAR can be
used from ground, air or space. When collecting LiDAR data from an aircraft, the
system mounted in the aircraft scans the ground or any required surface. A GPS
(Global Positioning System) is also integrated with LiDAR that keeps track of
aircraft’s location and attaches the locational parameter with the collected
data. Since the elevation and position of the aircraft changes during the
flight, the system calculates precise location of aircraft and with respect to
it, locates the rest of the data. This information is continuously recorded in
the computer automatically.
What are pulse and
return?
When the light is
emitted towards the ground from an airborne LiDAR system, one single dispatch
of light is called a pulse. When the light hits the respective object, it
reflects back towards the LiDAR system, that reflected light when it reaches
and detected by the system is called a return.
What is LiDAR output?
High-resolution maps
are the output of LiDAR procedure. LiDAR technology provides fine-scale and
spatially defined three-dimensional landscape information and map structural
components like elevation, dimension and density of the structures. At the start,
LiDAR data is stored as a series of points. LiDAR data can also be stored in
the form of contours lines. The most fascinating form of output of LiDAR is DEM
or digital elevation model. DEM is made when the scanned surface is represented
with continuous elevation values in 3D format along with the values’
co-ordinates.
DEM
How the height of the
object is calculated?
When the light is
emitted from the LiDAR system, the time is recorded. The time is again recorded
when the light reaches back after hitting the object below. Using the speed of
light and the time difference between pulse & return, the distance between
the LiDAR system and the top of that object is calculated. Then the distance
between the aircraft and the ground surface is determined. The ground elevation
is also calculated using GPS.
Is LiDAR data accurate?
The turbulence of the
aircraft during flight and its tilt are incorporated into the system so that
accurate data can be recorded. The angular measurements of pulse & return
are taken into account as well when calculating the elevation that gives
precise elevations of the objects and ground surface.
Where are applications of
LiDAR?
LiDAR is used to monitor,
record, store, quantify, classify, predict, and manage data in the fields of surveying,
construction site selection & evaluation, large scale land use planning, terrestrial
elevation modeling, flood modeling, hydrographic models, power lines management,
piping networks, forestry, archeology, agriculture, urban modeling, transport
planning, environmental monitoring &
modeling, climate change, atmospheric physics, geosciences, geography, geology,
tectonic activity mapping, and glacial data recording etc.
What are the benefits
of using LiDAR technology?
LiDAR increases humans’
capability to gather data, represent data, and to respond to that data.
Greater efficiency,
faster results.
Automatic 3D modeling.
Automatic locational
tag.
Large scale topographic
maps are achievable.
Making night time data
collection possible.
Urban and even rural
areas are quicker to survey.
Cost effective.
References:
Into the Third Dimension:
Benefits of Incorporating LiDAR Data in Wildlife Habitat Models. (WWW)
LiDAR applications in
surveying and engineering. (WWW)
A meta-analysis of terrestrial aboveground biomass
estimation using lidar remote sensing. (WWW)
A review of the role of active
remote sensing and data fusion for characterizing forest in wildlife habitat
models. (WWW)
Lidar remote sensing of laser-induced incandescence on
light absorbing particles in the atmosphere. (WWW)
Assessing the transferability of statistical predictive models for leaf
area index between two airborne discrete return LiDAR sensor designs within
multiple intensely managed Loblolly pine forest locations in the south-eastern
USA. (WWW)
By LiDAR geek:
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