…and all of it without having to use the strawberry milkshake protein powder that I got from Walmart. Â That stuff was horrible!!!
One of my favorite laser publications, Optics.org, posted this awesome article — dinosaur skeletons, LIDAR, and imagining the mass of dinosaurs when they were alive. Â The article is pretty cool, check it out here.
From the article:
A team at theÂ University of ManchesterÂ has developed a new method for doing so that shows promise, by applying a lidar scanning technique to one of the largest mounted dinosaur skeletons in the world. The findings are published in Biology Letters.
Starting from the principle that the best estimates of dinosaur mass come from a volumetric approach, whereby a model of the animal is created and its mass then calculated via its density, the team scanned a complete skeleton using a lidar scanner supplied byÂ Z+F, specialists in laser scanning and data capture.
I had to know more about this LIDAR business — LIDAR means Light Detection and Ranging. Â From the wikipedia:
In general there are two kinds of lidar detection schema: “incoherent” or direct energy detection (which is principally an amplitude measurement) and Coherent detection (which is best for doppler, or phase sensitive measurements). Coherent systems generally useÂ Optical heterodyne detectionÂ which being more sensitive than direct detection allows them to operate a much lower power but at the expense of more complex transceiver requirements.
In both coherent and incoherent LIDAR, there are two types of pulse models:Â micropulse lidarÂ systems andÂ high energyÂ systems. Micropulse systems have developed as a result of the ever increasing amount ofÂ computerÂ power available combined with advances in laser technology. They use considerably less energy in the laser, typically on the order of one microjoule, and are often “eye-safe,” meaning they can be used without safety precautions. High-power systems are common in atmospheric research, where they are widely used for measuring many atmospheric parameters: the height, layering and densities of clouds, cloud particle properties (extinction coefficient, backscatter coefficient,Â depolarization), temperature, pressure, wind, humidity, trace gas concentration (ozone, methane, nitrous oxide, etc.).
There are several major components to a LIDAR system:
- LaserÂ â€” 600â€“1000Â nmÂ lasers are most common for non-scientific applications. They are inexpensive, but since they can be focused and easily absorbed by the eye, the maximum power is limited by the need to make them eye-safe. Eye-safety is often a requirement for most applications. A common alternative, 1550Â nm lasers, are eye-safe at much higher power levels since this wavelength is not focused by the eye, but the detector technology is less advanced and so these wavelengths are generally used at longer ranges and lower accuracies. They are also used for military applications as 1550Â nm is not visible in night vision goggles, unlike the shorter 1000Â nm infrared laser. Airborne topographic mapping lidars generally use 1064Â nm diode pumped YAG lasers, while bathymetric systems generally use 532Â nm frequency doubled diode pumped YAG lasers because 532Â nm penetrates water with much lessÂ attenuationÂ than does 1064Â nm. Laser settings include the laser repetition rate (which controls the data collection speed). Pulse length is generally an attribute of the laser cavity length, the number of passes required through the gain material (YAG, YLF, etc.), and Q-switch speed. Better target resolution is achieved with shorter pulses, provided the LIDAR receiver detectors and electronics have sufficient bandwidth.
- Scanner andÂ opticsÂ â€” How fast images can be developed is also affected by the speed at which they are scanned. There are several options to scan the azimuth and elevation, including dual oscillating plane mirrors, a combination with a polygon mirror, a dual axis scanner (seeÂ Laser scanning). Optic choices affect the angular resolution and range that can be detected. A hole mirror or aÂ beam splitterÂ are options to collect a return signal.
- Photodetector and receiver electronicsÂ â€” Two main photodetector technologies are used in lidars: solid state photodetectors, such as silicon avalanche photodiodes, or photomultipliers. The sensitivity of the receiver is another parameter that has to be balanced in a LIDAR design.
- Position and navigation systemsÂ â€” LIDAR sensors that are mounted on mobile platforms such as airplanes or satellites require instrumentation to determine the absolute position and orientation of the sensor. Such devices generally include aÂ Global Positioning SystemÂ receiver and anÂ Inertial Measurement UnitÂ (IMU).
This scanning technology is actually pretty widely used all over the place — along with terrestrial map data from suppliers, the GPS companies’ travel vans are mostly fitted with LIDAR scanners. Â These scanners are actually pretty cool – the company listed in the article, Z+F UK, has some particularly interesting looking devices! Â Also, Radiohead apparently used lots of LIDAR capture to film their House of Cards video. Â Here’s a bit of them doing some scanning work:
Crazy. Â Also, if you’re one of those nerds like me who likes to comb through the images and content on places like NOAA and see the output from satellites at the various observation stations, check out the LIDAR stuff at the USGS (US Geological Survey) website.