LiDAR: Light Detection And Ranging

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LiDAR is an acronym for ‘light’ and ‘radar,’ a tool developed to detect targets and to use reflected light off of objects as a kind of visual sonar. Light Detection And Ranging (LiDAR) can determine how far objects are away from each other by shining a laser onto a target and analyzing the light that bounces back. LiDAR is used to create incredibly detailed maps in addition to assisting researchers in the fields of geography, archeology, geology, seismology, atmospheric sciences, laser studies, and much more.

LiDAR’s first applied use was in the 1960s and came soon after the invention of lasers. Used in combination with radar, LiDAR was originally used in atmospheric studies to measure clouds by the National Center for Atmospheric Research. LiDAR later became more publically known when the Apollo 15 mission used it to map the surface of the moon more accurately than ever before.

The technical aspects of LiDAR are many. LiDAR uses UV light and light close to infrared on the spectrum to target certain objects and analyze their distances based on the refraction of light that is bounced back. The theory is that objects of varying shapes, sizes, densities and distances will reflect light back at different speeds and thus create a high-resolution map of the surroundings.

LiDAR was used to Map Flooding from Hurricane Isaac. Source: USGS

LiDAR was used to Map Flooding from Hurricane Isaac. Source: USGS

Like Apollo 15 and the work done by atmospheric scientists to map the upper atmospheres, LiDAR is continuing to be instrumental technology in the future of space missions to planets like Mars, both for manned and unmanned missions. LiDAR technology can map surfaces of planets mankind can’t reach by space rovers (yet) and be integral for finding proper landing spaces for space vehicles in the future.

Most LiDAR is made up of the same basic components- the laser, a scanner and optics, photodetectors and receiver electronics, as well as position and navigation systems. The laser is generally eye-safe (meaning the laser isn’t strong enough to damage a human eye) except for very strong lasers used by atmospheric scientists to penetrate the highest reaches of the atmosphere.

The scanner, depending on its speed, develops images faster or slower depending on the quality and can scan a specific area. The optics of a LiDAR mechanism is developed to return a clear picture of what the laser and scanner have detected. Sensitive photodetectors are used to create a physical picture of the objects that have been scanned, all of which is mounted on platforms based on their use (i.e. airplanes, satellites, rovers, etc.). LiDAR can print in 2D or 3D.

LiDAR has many other practical applications including mapping crop yields in agriculture, mapping terrestrial and extraterrestrial bodies, studying the atmosphere and contributing to military technology. LiDAR is also used to detect objects underground and is vitally important for archeologists. LiDAR can find previously unmapped or unknown fault lines contributing to localized earthquakes as well as faults in building structures.

References

USGS. 2014. Light Detection and Ranging. Web access 5 January, 2015. https://lta.cr.usgs.gov/LIDAR

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