Lidar.

LIDAR (Light Detection and Ranging) is a remote sensing technology using the properties of scattered light to find range and get an object from the intended target. The method for determining the distance of an object is by using laser pulses. Such as radar technology, which uses radio waves, the distance to the object is determined by measuring the time interval between transmission of a pulse and detection of the transmitted signal. LIDAR technology has uses in the field of geomatics, archeology, geography, geology, geomorphology, seismology, physical atmosphere, and others. Another term for LIDAR is ALSM (Airborne laser swath mapping) and laser altimetry. Acronyms LADAR (Laser Detection and Ranging) is often used in a military context. The term is also used laser radar but do not touch because it uses laser light instead of radio waves which are the basis of conventional radar. LIDAR uses infrared light, ultraviolet, visible, or near the object image and can be used for various targets, including objects of non-metal, rock, rain, chemicals, aerosols, clouds and even a single molecule. A laser beam can be used to obtain a physical map features with very high resolution. LiDAR has been used extensively to study the atmosphere and meteorology. LIDAR instruments fitted to aircraft and satellites used for surveying and mapping. The most recent example is NASA's Advanced Research Lidar Experiment. In addition, lidar has been identified by NASA as a key technology to enable precision landing safest for future robotic and manned vehicle to the moon landing. In addition, there are various applications of LiDAR, as is often mentioned in the National Programme LIDAR datasets, USA.

Farming and Plantation.

LIDAR can be used to help farmers determine which areas of their land field to apply fertilizer distribution. LIDAR can make a map of the topology of the field and reveal slope and sun exposure of farmland. Researchers at the Agricultural Research Service call right, with LiDAR datasets able to obtain topology information with the condition of agricultural land from previous years. From this information, researchers can determine the category of agricultural land into high-grade, medium, or low - to produce a distribution zone land conditions. This technology is valuable to farmers because it shows which areas to implement the spread of fertilizer in order to achieve the highest yields.

Archeology.

LIDAR has many applications in the field of archeology, including assisting in the planning field survey, mapping feature under the forest canopy, and give a broad picture-detail, and others. LIDAR can also help archaeologists to create a digital elevation model (DEM) high resolution of archaeological sites, which can reveal the hidden micro-topography by vegetation. LIDAR and its derivatives can be easily integrated into a Geographic Information System (GIS) for analysis and interpretation. For example, in Fort Beausejour - Fort Cumberland National Historic Site, Canada, features previously undiscovered archaeological have successfully mapped associated with Fortress siege in 1755. Features which can not be distinguished in the field or through aerial photography identified by overlaying hillshades of DEM made with lighting from various angles. With LIDAR, the ability to produce high-resolution datasets fast and relatively inexpensive. In addition to efficiency, ability to penetrate the forest canopy has been providing discovery features that can not be distinguished by traditional geospatial methods and difficult to reach through field surveys.

Biology and Conservation.

LIDAR widely applied in the field of forestry. Canopy height, measurements of biomass, and leaf area can all be studied using LIDAR system. Topographic maps can also be produced easily from LIDAR, including for use in the production variant of forest maps. Another example, Redwood Rescue League is conducting a project to map the height of trees on the north coast of California. LIDAR enable research scientists to not only measure the height of trees that previously uncharted, but to determine the redwood forest biodiversity. Stephen Sillett who worked on the North Coast League LIDAR project claim that this technology will be useful in guiding future efforts to preserve and protect the old redwood trees.

Geomorphology and Geophysics.

High-resolution digital elevation maps generated by LIDAR has spurred significant advances in the field of geomorphology. LIDAR ability to detect subtle topographic features such as river terraces and the edge of the river channel, measuring the elevation of the ground surface beneath the canopy of vegetation, resulting in a spatial derivative elevation, and detecting changes in elevation on the Earth's surface. LIDAR data collected by private companies and academic consortium in support of the collection, processing and archiving LIDAR datasets available to the public. National Center for Airborne Laser Mapping (NCALM), supported by the National Science Foundation, collect and distribute LiDAR data to support scientific research and education in various fields, particularly the geosciences and ecology. In geophysics and tectonics, the combination of LIDAR and GPS-based aircraft have evolved into an important tool for detecting faults and measure the material removal. The output of these two technologies can produce extremely accurate elevation models for terrain that can even measure the elevation of the ground through the trees. This combination has been used to find the location of the Seattle Fault in Washington, USA. This combination is capable of measuring the material removal in Mt. St Helens using data from the glacier before and after appointment in 2004. monitor airborne LIDAR system has the ability to detect subtle increase or decrease the amount of material. A NASA ICESat satellite-based system that includes a LIDAR system is applied for this purpose. NASA's Airborne Topographic Mapper is used extensively to monitor glaciers and coastal change analysis. This combination is also used by soil scientists when making land surveys. Terrain modeling detail allows a soil scientist to see changes in the form of land slope and show patterns in the spatial relationships.

Transportation.

LIDAR systems have been used in the Adaptive Cruise Control (ACC) for the car. Systems such as those by Siemens and Hella using lidar device mounted on the front of the vehicle, such as bumpers, to monitor the distance between the vehicle and each vehicle in front of him. Vehicle in front slows down or too close, ACC applies the brakes to slow the vehicle. When the road ahead is clear, ACC allows the vehicle to accelerate to the speed preset by the driver.

Military.

Some lidar applications for the military provide higher resolution imagery to identify enemy targets, such as tanks. LADAR name is more commonly used in the military. Examples of military applications such LIDAR Airborne Laser Mine Detection System (ALMDS) for counter-mine warfare with Arete Associates. A NATO statement (RTO-TR-SET-098) states that: based on the LIDAR system, the task force recommends that the best choice for near-term applications (2008-2010) of the stand-off detection system UV LI. Long-Range Biological Standoff Detection System (LR-BSD) was developed for the US Army to provide early warning on biological attacks. It is air system brought by helicopter to detect artificial aerosol cloud containing biological and chemical weapons at long distances.

Monitoring and Supporting Technical.

Theoretically lidar consists of three components, namely :

• Global Positioning System (GPS)
In the LIDAR system, GPS positioning system is used as a flying vehicle in 3D (X, Y, Z or L, B, h) of the reference system specific. when doing LIDAR survey. Differential positioning is done so that it can observe objects that are stationary position or bergerak.Karena position measurements performed in real time, the GPS determination method was called Real Time Kinematics Differential GPS (RTK-DGPS).
• Inertial Navigation System (INS)
INS is a navigation system that is able to detect changes in the geographical, speed changes, and change the orientation of an object. The system is capable of measuring large changes in flying vehicle orientation angles to the direction of the north, a large movement of the angle of rotation of the flying vehicle-axis horizontal axis, flying vehicle acceleration, until the temperature and pressure of the air around the vehicle to fly. From the results of measurements that can be performed by the INS, can produce three-dimensional information such as orientation and position of flying vehicle.
• Laser Sensor
LIDAR sensor is used to emit a laser beam to an object and record the wave reflection back after about the object. In general wave emitted by the sensor consists of two parts, namely the green wave and infrared waves. Green wave function as a wave penetration if a laser beam on the water area. Green beam is used to measure the depth of the data, while the infrared light is used to measure the topography of the data or the earth's surface. LIDAR sensor strength is closely associated with:
• The power of the laser beam generated
• Coverage of the laser beam wave
• The amount of laser light generated per second
LIDAR sensor has the ability to return multiple measurements. Multiple return is used to determine the shape of the object or vegetation that covered the ground. Waves emitted and reflected not only on the surface of the ground, but also on the objects that exist on the surface of the ground. Each reflection was measured intensity, in order to obtain a picture or shape of objects that cover the surface of the soil.

LIDAR measurements.

The working principle is generally LIDAR sensor emits a laser beam on the target then the light is reflected back to the sensor. Beam that is captured and analyzed by the detector equipment. Changes in the composition of the light received from a target is set as an object character. Travel time when the light emitted and received back needed as a variable in the computation of the distance from the object to the sensor.                              

In the selected vehicle (aircraft) mounted Laser Scanner, GPS, and INS. Based on the desired scale and broad product scope, it can be determined flyway. At a predetermined flight path of the aircraft to shoot / penyiaman (scanning). Well, at the time of laser scanners do penyiaman along the flyway, at any given time interval recorded position (using GPS) and the orientation (using INS). This process is carried out until all the planned flight path can disiam. At this stage of data processing can be divided into 3 parts, the processing of GPS data, INS, and LIDAR. Processing of GPS and INS conducted separately by post processing to obtain the position and orientation of the laser scanner along the trajectory (trajectory flight path).

The principle of radar signal processing was done to determine the distance between the Laser Scanner with objects (eg roof of the building. It is quite interesting here is to be found 4 coordinate system, namely: System coordinates GPS receivers, INS coordinate systems, coordinate system Laser Scanner, and the map coordinate system . in the context of photogrammetry, 4th coordinate system can be connected in the form of a vector. the vector map coordinate system is the vector sum of the resultant vector coordinate system with INS and GPS receiver Laser Scannner.

Preliminary data after Lidar measurements obtained in the form:

1. The coordinates of control points (BM) field measurements using GPS Geodetic (Adjustment report) and the results of kinematic GPS plane.
2. RAW Lidar Data in native format file system LAS
3. Image metric medium format color photographs in digital format
4. Map of the flyway.

1. Do Lidar Mapping.

Lidar stands: Light Detection And Ranging, which means (in free translation) is the object recognition from the air (airborne) using light (laser) and measuring the distance from the sensor to the object to be recognized.
The laser beam is a beam that has not seemed Infrared waves have a wavelength of about 1000 nanometers, because of the specifications, the laser can penetrate the foliage to reach the soil surface and is reflected back to be captured by a laser sensor to note the difference of time spent starting out from the sensor to re-arrested sensor. So that the distance obtained or called by Range is half the round-trip time multiplied by the speed of propagation of a laser is used. The laser beam used to be harmless to the human eye (eye safe).
If the position coordinates and elevation of the laser sensor is known (with a tech GPS / INS), then any object that reflects the laser beam can be known position and elevation to the reference plane used.
So that each position coordinates and elevation can be used for mapping, in particular topographic mapping is utilizing ground surface elevation that reflects the laser beam scanning when done. Furthermore, the elevation of any point on the surface of the soil can be used to construct the Digital Surface Model / MPDyang useful for modeling the surface area and the manufacture of contour lines for mapping.
To present an overview of the soil surface planimitris details such as Roads, Building, River, transmission lines, such as land cover types of vegetation, agricultural areas, plantation, cultivation, mining, water bodies DLS region, done by drawing on a digital aerial photos as a complete system Lidar .

2. What Lidar System Components.

There are three main components, namely Lidar system: Laser generator-GPS / INS-digital camera.
Laser generator function for the target object from an aircraft and measures the travel time when the target object. Normally equipped with a data recorder. The laser beam is not lengsung dibidikan to object on the ground, but were fired through a glass shaken so that it will form a shot towards the right-left of the sensor. If the sensor moves being taken by plane, then shots of laser generator is a collection point with a certain width (normally form a 60º angle from the axis of the establishment) that will form the swath (width shooting elongated in the direction of movement of aircraft fly) GPS / INS is used to determine the position and the deviation angle from the direction of the X axis, Y axis and Z axis of the laser generator so that each laser shot of the object can be determined coordinates (Latitude-Longitude) and elevation of the reference set. The digital camera is a camera that can record the target object ckupan laser beam with a width equal to the laser beam swath coverage

3. What is the Fullwaveform Lidar technology in the system and what the benefits are used in Indonesia.

During the implementation of the Lidar scanning the laser beam pointing the way toward the object surface soil, every shot of the object will be reflected back to the laser generator, the system is called the leading edge of technology. So it is possible reflection of the first object back to the generator called the first return, followed by the system last reflection on the object that is the ground, and return to the generator and reflection between the first and last return. Systems like this are most Lidar system in general. Other Lidar system is a system called Fullwaveform technology, wherein each of the reflected laser beam on the object and will continue to further the objects so on until the final reflection which is the ground level. So that each will have a range of shooting multiple wave for each object that is passed.
Criteria last return in the form of the ground is the length of the object that is 6 milliseconds. If the laser beam on the object of more than 6 milliseconds then the light should go back to the generator which berararti is the last return.

4. Which Lidar system components that determine the accuracy of the results
Laser light radiated strength and accuracy when the laser is used to measure the travel time will determine the accuracy of a laser range. Accuracy of GPS / INS will determine the accuracy of the coordinates and elevation position sensor accuracy resulting in the targeted object.

5. Can Lidar done at night or through clouds and watery regions in the ground
Implementation of Lidar acquisition can be done at night because Lidar uses his own energy in the form of laser light. The laser beam can not penetrate the clouds which are particles of water, watery, where the nature of the laser beam can not penetrate the water body. Thus, if a laser beam shooting on the watery region such as beach, lake, river width, etc. swamp region, the laser light with infrared waves can not penetrate the water body.

6. Do Lidar scanning can be used for underwater mapping.

Can, where Lidar uses light with a specific wavelength (normally blue light with a wavelength of 300-400 microns in combination with infrared rays. Laser to use your infrared rays are used to determine the elevation of the water surface, while the lidar with blue light will penetrate the water body sampi with certain depth to the bottom surface of the water. So the depth of the bottom waters is known to be mapped.

7. What is meant by the point-cloud, bare-earth from Lidar

Point cloud is kumulan point shots on Lidar scanning laser that has been processed so as to have the position coordinates and elevation in accordance with the references. While Bare-earth is the point cloud which have been incorporated only at ground level only (titik2 bare soil surface)

8. What is the use of digital photos on Lidar Mapping

    Digital photos on Lidar mapping is used for:
      • Completing the boundary lines that have different ground surface elevation strikingly like the line where the cliff, or a line on the dike elevation change drastically, which is called the breakline. Breaklini serves to form the terrain or the natural contour lines in order.
          • As a means of Lidar data quality control
        • As a complement lidar elevation data in case the data can not penetrate dense vegetation vegetation because although it has been done a certain way like a cross scanning run.
        • As for the media portrayal planimetric elements such as Roads, rivers, land cover, etc. that can be done as well as stereoscopic 3D monoskopik
         • As a complement to the data for specific purposes as aerial photographs can produce Map Photos more informative than the map line.

9. Can digital photos done simultaneously during the data acquisition Lidar

Supposedly digital aerial photography is done in conjunction with the acquisition of Lidar to be more efficient and obtain accuracy comparable to a Lidar, the data is georeferenced using GPS / INS

10. What are the requirements for a digital photo Lidar Mapping

Aerial photograph should be based on the requirements of normal Fotogrametry ie aerial photographs that have pertampalan forward direction of flight path of 60% or more in order to have triplelap area, and pertampaln laterally by 30%. There should not be a gap between photos or between flyway for variation scale mountainous region.

11. How Lidar acquisition and digital photos to terrain

Joint lidar acquisition of aerial photography in mountainous regions should use a management system based on the position-controlled predetermend v / h (speed variation of the terrain elevation) using GPS navigation computer.

12. Can the data Lidar strike the ground if that is in the scanning area is fairly dense vegetation air

One estimate whether the laser can penetrate the luxuriance of vegetation or not, can be carried out under the inspection of vegetation environment, if a person is under the environment vegetation can still see the sun, meaning Lasers can also penetrate

13. What to do if the data Lidar can not reach the ground

To anticipate the laser beam does not penetrate the dense vegetated area, do Cross-run with different flight direction, so the cost will depend on the Lidar Mapping acquisition system that will generate its own accuracy. With the cost of the cheaper, cross the run was not done so potential laser beam will not strike the ground and consequently derived elevation data is limited and ultimately will provide output that is not perfect. Only data2 laser above the ground that are less useful for topolah obtained. If you cross the run has been carried out but did luxuriance of vegetation can not penetrate the laser beam, is the latest effort by adding elevation data are fotogrametry that the pairs of aerial photographs stereo3D. Additional extraction point elevation is done by the system using digital fotogrametry Algorithm (pixel-based)

14. What is the accuracy of elevation results Lidar Mapping

  Factors Impiris accuracy Lidar Mapping in Indonesia are as follows:
   • Horizontal Accuracy ± 20 cm
   • Accuracy ± 30cmoogle.com/ elevation
Thank you for reading this article. Written and posted by Bambang Sunarno. sunarnobambang86@gmail.com
author:
http://schema.org/Personal.
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name: Bambang Sunarno.
http://www.primadonablog.blogspot.com/2014/12/lidar.html
DatePublished: December 24, 2014 at 19:02

Tag : Lidar.

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