What is LiDAR technology and how does it work?
LiDAR has become extremely important to the discipline of archaeology. Discover more about what it is and how it works in this series of blog posts from Geospatial World.
LiDAR, or light detection and ranging, is a popular remote sensing method used for measuring the exact distance of an object on the earth’s surface. Even though it was first used in the 1960s when laser scanners were mounted to aeroplanes, LiDAR didn’t get the popularity it deserved until twenty years later. It was only during the 1980s after the introduction of GPS that it became a popular method for calculating accurate geospatial measurements. Now that its scope has spread across numerous fields, we should know more about LiDAR mapping technology and how it works. What is LiDAR technology and how does it work? Here are a few insights about it that are good to know.
Image Courtesy: Wired.co.uk
LiDAR Technology
According to the American Geoscience Institute, LiDAR uses a pulsed laser to calculate an object’s variable distances from the earth surface. These light pulses — put together with the information collected by the airborne system — generate accurate 3D information about the earth surface and the target object.
There are three primary components of a LiDAR instrument — the scanner, laser and GPS receiver. Other elements that play a vital role in the data collection and analysis are the photodetector and optics. Most government and private organizations use helicopters, drones and airplanes for acquiring LiDAR data.
Types of LiDAR Systems
LiDAR systems are divided into two types based on its functionality — Airborne LiDAR & Terrestrial LiDAR.
Airborne LiDAR
Airborne LiDAR is installed on a helicopter or drone for collecting data. As soon as it’s activated, Airborne LiDAR emits light towards the ground surface, which returns to the sensor immediately after hitting the object, giving an exact measurement of its distance. Airborne LiDAR is further divided into two types — Topological LiDAR and Bathymetric LiDAR.
Terrestrial LiDAR
Unlike Airborne, Terrestrial LiDAR systems are installed on moving vehicles or tripods on the earth surface for collecting accurate data points. These are quite common for observing highways, analysing infrastructure or even collecting point clouds from the inside and outside of buildings. Terrestrial LiDAR systems have two types — Mobile LiDAR and Static LiDAR.
How Does LiDAR Work?
LiDAR follows a simple principle — throw laser light at an object on the earth surface and calculate the time it takes to return to the LiDAR source. Given the speed at which the light travels (approximately 186,000 miles per second), the process of measuring the exact distance through LiDAR appears to be incredibly fast. However, it’s very technical. The formula that analysts use to arrive at the precise distance of the object is as follows:
The distance of the object=(Speed of Light x Time of Flight)/ 2
LiDAR can be used to accomplish many developmental objectives, some of which are:
Oceanography
When the authorities want to know the exact depth of the ocean’s surface to locate any object in the case of a maritime accident or for research purposes, they use LiDAR technology to accomplish their mission. Other than locating objects, LiDAR is also used for calculating phytoplankton fluorescence and biomass in the ocean surface, which otherwise is very challenging.
Digital Elevation or Terrain Model
Terrain elevations play a crucial role during the construction of roads, large buildings and bridges. LiDAR technology has x, y and z coordinates, which makes it incredibly easy to produce the 3D representation of elevations to ensure that concerned parties can draw necessary conclusions more easily.
Agriculture & Archaeology
Typical applications of LiDAR technology in the agriculture sector include analysis of yield rates, crop scouting and seed dispersions. Besides this, it is also used for campaign planning, mapping under the forest canopy, and more.
Agriculture & Archaeology
Typical applications of LiDAR technology in the agriculture sector include analysis of yield rates, crop scouting and seed dispersions. Besides this, it is also used for campaign planning, mapping under the forest canopy, and more.
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Bhupendra holds a post-graduate degree in management. He blogs about startups, internet marketing, emerging technologies, online money making ideas, IoT, and entrepreneurship. When not working, he can be caught reading books.
5 ways LiDAR is transforming the world before our eyes
LiDAR has multiple applications and utilities and their full scope would soon extend beyond our imagination as it unravels in the future. LiDAR is among the array of technologies that together form the basic building block of the new age of automation. From the basic applications in sensors to 3D printing, 3D scanning, modeling and smart cities, LiDAR is transforming the world in a number of ways. Let’s have a look at some of the main application areas of LiDAR
LiDAR in Augmented Reality (AR)
LiDAR has multiple applications and utilities and their full scope would soon extend beyond our imagination as it unravels in the future. LiDAR is among the array of technologies that together form the basic building block of the new age of automation. From the basic applications in sensors to 3D printing, 3D scanning, modeling and smart cities, LiDAR is transforming the world in a number of ways. Let’s have a look at some of the main application areas of LiDAR
LiDAR in autonomous vehicles
Autonomous cars are expected to hit the roads soon and they would revolutionize the automobile sector completely. Without LiDAR, autonomous vehicles are inconceivable. LiDAR should be called the eye of an autonomous vehicle as it looks at the surroundings of the vehicle, calculates distance, identifies obstructions ahead, illuminates objects with a laser and then creates a high-resolution digital image. LiDAR is also used to avoid collisions by measuring the distance between a car and any other car in front of it. This is done by mounting a LiDAR on the bumper or the roof. The Adaptive Cruise Control system in an autonomous car gets the information from the LiDAR sensors, using which it decides when to apply the brakes, slow down or accelerate.
LiDAR in climate change mitigation
The ultra-high resolution and precise imagery of LiDAR capture and highlight even the minutest details. For this reason, LiDAR is increasingly being preferred by scientists and geologists. LiDAR can help track deforestation and agriculture patterns more efficiently than any other method. And the data obtained also pinpoints what was left unobserved in previous estimations, which makes it all the more reliable.
NASA has developed a LIDAR-based instrument called GEDI (Global Ecosystem Dynamics Investigation) for the International Space Station that provides a unique 3D view of Earth’s forests and helps provide information about the carbon cycle that was previously not available. GEDI provides vital information about the impact that trees have on the amount of carbon in the atmosphere. Using the info, the scientists are now able to figure out the exact level of carbon that forests store and the number of trees that should be planted to offset the effect of greenhouse emissions
Surveying
Surveying is among the most widely known application areas of LiDAR. LiDAR surveying is used in the fields of construction, urban planning and examining the topography of a region. LiDAR surveying collects data very fast and thus is superior to conventional forms of surveying. Spatial models created using LiDAR have a negligible scope of error margin, saves a considerable amount of money and improve the final decision making. In surveying, point data is converted into a surface, or Digital Elevation Model (DEM). The DEM can be of any texture depending on the application and density of the data. After the surface is created, analysis can be done, as required.
Archeology
To unearth old archeological sites, LiDAR is proving to be an important asset especially because of extraordinary detailing that it offers. LiDAR saves time as well as the effort of the archeologists and allows them to create models that were almost impossible to create earlier. Stunning 3D images of an ancient Mayan city were created by two archeologists using LiDAR which offers unprecedented insight into that ancient city.
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Former Assistant Editor, Geospatial Media & Communications. Intrigued by the intersection of society, politics, popular culture and technology, he believes that the key to unraveling present complexities lie in the wisdom of the past.
Teledyne Optech Titan LiDAR enables discovery of Mayan ruins in Guatemala
After the collapse of the Mayan civilization, their cities and monuments were quickly covered by thick rainforest, hiding the ancient civilization from airborne observation and making it very difficult to survey on foot. Flying high above the rainforest, Titan’s lasers penetrated the canopy to collect almost a million data points per second from the forest floor, giving archaeologists a “bare earth” view of the structures underneath. Having rapidly covered 2,100 km2, Titan’s data revealed massive amounts of ruins hidden below the forest, showing that their urban centers were significantly larger than archaeologists had previously thought.
“We are incredibly proud and excited that our award-winning Titan multispectral lidar sensor has contributed to this spectacular discovery,” said Michel Stanier, EVP and General Manager of Teledyne Optech. “Titan’s ability to strip away overlying vegetation and map wide areas very quickly and accurately makes it an important tool for archaeologists, and we expect to see many more discoveries coming from it and our other airborne laser terrain mappers.”
Optech Titan is the first commercial multispectral lidar sensor to incorporate 3 independent laser wavelengths into a single sensor design, with beams at 532, 1064, and 1550 nm (0.5/1.0/1.5 microns) and a ground sampling rate of 300 kHz per beam. Because Titan uses both green and infrared channels, it is capable of simultaneous water depth mapping and high-precision 900-kHz topography. Titan can also be used for purposes such as vegetative and forestry applications, which require multiple wavelengths for improved classification accuracy and carbon credit counting initiatives.
Teledyne Optech’s Titan sensor was used by the University of Houston’s National Center for Airborne Laser Mapping (NCALM) to reveal extensive Mayan ruins in Guatemala. LiDAR technology was able to identify hundreds of previously unknown structures, including raised highways, and complex irrigation and terracing systems.
Blog posts courtesy of the website Geospatial World: Advancing Knowledge for Sustainability
https://www.geospatialworld.net/blogs/what-is-lidar-technology-and-how-does-it-work/
https://www.geospatialworld.net/blogs/5-ways-lidar-is-transforming-the-world-before-our-eyes/
https://www.geospatialworld.net/news/teledyne-optech-titan-lidar-enables-discovery-extended-mayan-ruins-guatemala/