LiDAR is a remote sensing technique that utilizes light from a laser to collect measurements. It is used to create 3D models and maps of objects and environments, and can be employed to join objects and rooms in 3D and superimpose photographic images on top, a process known as photogrammetry. This technology has the potential to revolutionize the way we capture data for practical uses such as home improvement, social media, journalism, and more. The LiDAR system is highly accurate, with a vertical accuracy of around 15 cm and a horizontal accuracy of 40 cm.
Linear LiDAR typically has a stripe width of 3,300 feet, while Geiger's LiDAR can scan widths of 16,000 feet. In a forest, the laser pulse goes downward and when light hits different parts of the forest, the “return number” is obtained. Digital elevation models (DEMs) are naked terrestrial (topographic) models of the Earth's surface, while digital terrain models (DTMs) incorporate contours. Canopy height models (CHM) give you the actual height of the topographic features of the ground.
The creation of LiDAR profiles was the first system that was used in the 1980s. It specialized in straight-line functions, such as power lines. The profiling LiDAR sends an individual pulse on a line. Small LiDAR is what we mainly use today and it scans at a scan angle of about 20 degrees.
If it exceeds 20 degrees, the LiDAR instrument can begin to see the sides of the trees instead of looking straight down. Ground penetrating radar (GPR) is another option for capturing data from underground. In some types of soil, the depth of penetration averages about 5 meters. But can Lidar detect buildings or human skeletons? Could you find the skeletons of the 50,000-man army of the Persian king and Egyptian pharaoh Cambyses, which was swallowed up by a sandstorm in the Sahara desert in 523 BC? Soldier skeletons may be buried deep under sand.
My municipality is currently conducting a LIDAR survey to determine the loss of urban trees in relation to development. More than half of the residents agree that the tree canopy is almost adequate and that a regulation on trees should be enacted to protect mature trees. The outcome of this LIDAR study will determine if 20 cm trees in DBH should be preserved or not to help mitigate climate change, stabilize slopes, etc. The “ghostly images” seen in television programs about airports and cathedrals are created by scanning an object from both sides and coordinating it on a computer.
There are also short-range versions of lidars that can map surfaces up to 4 feet x 4 feet but with varying heights. The DIAL (Differential Absorption LiDAR) is used to identify particular forms of gas in the atmosphere, while the LiDAR Raman measures concentration and the LiDAR Doppler measures wind speed. UAV LiDAR has been one of the most anticipated technologies of the last 10 years as it has changed the way surveyors capture data and has significantly reduced costs. When collecting data with a LiDAR system, point cloud, all LiDAR data points are not ranked as to what they are affecting.
There are many applications for LIDAR technology including atmospheric absorption measurements, cloud profiling, wind measuring, aerosol studying, quantifying atmospheric components, and more. If you're looking for free LiDAR data sources, here's a list of 6 so you can start your search: USGS Earth Explorer; OpenTopography; NOAA Digital Coast; OpenLidarData; OpenDataSoft; and OpenDataMonitor. LiDAR technology has come a long way since its inception in 1980s and continues to evolve with new applications being discovered every day. It has revolutionized remote sensing by providing accurate measurements with high resolution data that can be used for various purposes such as mapping terrain features or detecting objects underground.
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