Wednesday, 24 August 2016

LiDAR – The Technological Glaze

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)

What is LIDAR? (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)


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1 Response to "LiDAR – The Technological Glaze"

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