Lidar-

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LiDAR is a very fast growing remote sensing technology which becoming quite important issue to be discussed in Governmental, industries, professionals, Students levels. It is a quickly updating technology which we are interested to discuss about it in this section.

Even though originally it was for usage of measurement of terrain,the interest in LiDAR has been grown through time in it’s last two decades of age in areas like:

  • DEM developing
  • Its application independent to cloudy/sunlight conditions unlike the other remote sensing technologies.
  • Its applications in urban, forestry and agriculture to record quality forest attributes and object heights to sub meter accuracy level.
  • Surface height estimation and the structures of forests especially assessed by this technology.

Due to these specialties it did not take time to be adopted by the geomatics, agriculture and forestry industries.

As you may know LiDAR stands for Light detection and ranging technique which uses leaser to measure ranges directly and heights and elevations indirectly.

Even though it has a kind of similarities with the other mapping technologies like radar and sonar, it is different because it uses light instead of radio or sound.

Eye Affection of Laser: Leaser is a light portion of a electromagnetic spectrum which lies b/n green and Near-Infrared of which type strongly reflected off of vegetation. Most of them are around 1064 nm wave length which impossible to see them with naked eyes. Pulses affects eyes but the Australian studies finds out some googles as solutions to secure the affection and became safe for all species and will not be a negative impact anymore on eyes.

LiDAR is an active type of remote sensing technology unlike of (areal photography, Landsat and spot which are all passives), due to the system emits light as a pulse and receives a reflection back as a Return. This will make the system more controllable using some sort of sensors in the platform. And with that sense we can say that this is an accurate technology.

There are three most common data collecting ways in LiDAR.

  • Terrestrial using some forms of scanners on a tripod or on a vehicle
  • In air on an air plane, UASs
  • Airborne LiDAR┬ábathymetric technology generally use 532 nm frequency.

Air borne LiDAR is the most available way of the technology. Therefore airborne data is the most freely available in the observatory networks(National Ecological Observatory Networks) now a days.

lidar-scanThe components of LiDAR System are

  • LiDAR unit
  • GPS
  • IMU and
  • Computer.

 

How LiDAR Works: The part of the system enabling laser scanning from side to side, is the LiDAR unit, where as GPS is used to measure the x,y,z position of the system on the aircraft. Here in the leaser’s pulse and Return, the system can calculate the height of the system from the surface, that the Return is reflected. So together with the GPS height and leaser measurements those are already calculated, the basic elevation of the surface will be indirectly computed.

And finally the pitch, yaw and roll measurements from IMU, and the angles b/n the Nadir-line and each of the offset-ed Pulse (off Nadir pulses) , both will be considered by the computer of the system, to calculate the accurate heights of each and every surface points on which the Returns are reflected back from.lidarimages-3

Number of Returns: The leaser that reaches to a canopy will not be returned direct only from the top of the canopy, but it will continue to reach to the branches, then the possible available shrubs and finally to the ground before returned back to the LiDAR system. And that is this ability of the LiDAR system, of recording all the available information from the top of the canopy to the ground that makes it unique, and highly valuable to plant study science. Because all the reflected backs Returns tells all the available information not only on the top but also under the canopy all the way to the ground. The shape, density, the possible available shrubs and structures of the forest will be uncovered in this process.

Application

The application of LiDAR system includes:

  • Agriculture in Classification in plant species, feature extraction, Reflectance features, Geometrical Features
  • Archaeology
  • Autonomous vehicles
  • Biology and conservation
  • Geology and soil science
  • Atmospheric remote sensing and meteorology
  • Law enforcement
  • Military
  • Mining
  • Physics and astronomy
  • Rock mechanics
  • Robotics
  • Spaceflight
  • Surveying
  • Transport
  • Wind farm optimization many more

Sigma Spaces’s Single Photon LiDAR The Next Generation LiDAR Capabilities

The airspace’s optical instrumentation company Lincoln Laboratory has pioneered in the development of mid and long infrared (IR). In the development process, it was possible to hybridized an Infrared (IR) detector to a readout integrated circuit to form a focal plane array.

Single photon LiDAR (SPL) is a system developed by the company for NASSA. The technology is also essential very helpful and profitable for the other industries like Geo systems. SPL is the LiDAR capable of detecting single photons (single particle of light) which makes the efficiency of the overall system higher than all the systems ever known before. With this capability it was possible to divide the leaser beam spectrum in to multiple hundred beams. This intern enables to identify the terrain, wall or water and also some atmospheric instruments is made using this photon counting technology. With single photon LiDAR a range of measurement as much as 6 million times/sec could be provided, which is a mile beyond (about 6 times as effective as hexagon latest generation LiDAR sensor) and other commercial instruments capabilities.

Relations With Leica Geo-system: This capability attracts the industries like Leica Geo-system to consider this technology for their imagery programming by adding elevation component to it. This efficiency can make the future mega projects that the Leica Geo-system may have feasible, in addition to getting wider spread adoption of the technology for their commercial instrument productions.

Space Science Application: The application of this new technology will also be expected to be used in mapping asteroids and planets in the process of attempting the plan to land on the planets like Mars by mounting it on the space craft that will be employed for this project. Generally it can be said that it is the technology which is revolutionizing the whole LiDAR system in to it’s completely new dimension.

The above note is taken from Wikipedia, POB (Point of Begining), Geoinformatics
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