LIDAR stands for LIght Detection And Ranging. LIDAR is analagous to RADAR, only uses light from a laser instead of radiowaves to remotely sense distant objects. Because the wavelength of light is small, LIDARs can detect very small objects.

The LIDAR Technique

An aerosol LIDAR works by emitting a laser beam into the atmosphere. The laser light is scattered by particles, with some “backscattered” to a telescope placed alongside the laser. Because the speed of light is known, the distance to the particle layers can be determined from the time taken for the light to return.

More advanced LIDARs can also take advantage of the properties of the returned light. From these, certain characteristics about the atmosphere can be determined, such as optical depth and particle identification (volcanic ash, smoke, marine aerosols, dust).

LIDARs plot every laser pulse individually. This means that energy per pulse is of the highest importance, since the more energy a laser pulse has, the further it will reach into the atmosphere before being scattered away. Stacking or integrating data can improve data quality but cannot do much for the range. This is why Raymetrics LIDARs use some of the most powerful industrial lasers on the market.

Uses of LIDAR
LIDARs have been around since the 1960`s, but only recently have the applications for this technology begun to become more widely known. Raymetrics has been in operation since 2002, providing LIDARs initially to the academic community. Over the past few years however, clients have increasingly come to Raymetrics from operational and commercial sectors.

Probably the most well-known atmospheric LIDAR is the wind Doppler LIDAR. These are different from the aerosol type LIDARs produced by Raymetrics. Wind LIDARs detect movement of particles, whereas aerosol LIDARs detect the particles themselves.

Aerosol LIDARs are increasingly becoming standard technology, particularly in the aviation and meteorology sectors. Ceilometers are in effect basic model LIDARs, with small telescopes and low-energy lasers in order to detect the cloud base. LIDARs can however provide much more information (e.g. incoming cloud base, fog detection, and remote visibility measurement). `ISO 28902-1:2012 - Ground based remote sensing of visual range with LIDAR` shows that LIDAR is now a standard technique for measuring visibility. LIDAR is also able to solve specific issues such as absolute identification of volcanic ash, along with providing ash layer altitudes.

As time goes on, the applications for atmospheric LIDARs are rapidly increasing and Raymetrics, as the first atmospheric LIDAR company in the world, now finds itself at the forefront of a new and booming industry.

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