LIDAR Light Detection and Ranging Kate Whalen PHY 3903 Nov. 25, 2005.
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Transcript of LIDAR Light Detection and Ranging Kate Whalen PHY 3903 Nov. 25, 2005.
LIDARLight Detection and Ranging
Kate Whalen
PHY 3903
Nov. 25, 2005
Outline
• Some applications• How lidar works• Examples of current
lidar projects– Purple Crow Lidar
– Dalhousie Raman Lidar
Applications
• Distance measurements
• Atmospheric composition
• Weather
• Mapping
• Speed measurements
Lidar Basics
• Active remote sensing• Light is emitted,
scattered, and detected.
• Since we know the speed of light, we can measure the distance travelled!
Details• 3 main parts
• Transmitter– Example: Pulsed Nd:YAG
laser (532 nm)• Low beam divergence
• Narrow spectral width
• Receiver– Optical telescope
• Detector– PMT
– Chopper• Eliminates near-field returns
Purple Crow Lidar (UWO)• Detector consists of a 2.65 m
mercury mirror, rotating at 10 rpm– Parabolic mirror
• 532 nm Nd:YAG laser used for Rayleigh scattering– Elastic scattering at 30-90 km
• Obtain T(z) from density profile– Assumptions
• Hydrostatic equilibrium
• Ideal gas
(z) z2N(z)
P RT
P gz
PCL Projects
Dalhousie Raman Lidar• CABOT Observatory
– Canadian Atmosphere-Biosphere Observations Trailer
• 607 nm Nd:YAG laser• Raman scattering
– Inelastic scattering (change in rotational or vibrational energy)
– Frequency of scattered photon depends on temperature, type of molecule
• Investigates atmospheric aerosols & clouds– Transboundary pollution
transport
CABOT Projects
In Conclusion…
• Lidar is an example of physics for the benefit of the planet!
References• Thanks to Dr. Bob Sica and the PCL group at UWO!
• Argall, P. S. & R. J. Sica, Lidar (Laser Radar). In The Encyclopedia of Optics, Vol. 2, Ed. T. G. Brown et al., Wiley-VCH, Weinheim, 2005.
• Duck, T. J. et al., Lidar measurements of atmospheres. Physics in Canada 61 (5) 247-252, 2005.
• Sica, R. J. et al., Lidar measurements taken with a large-aperture liquid mirror. 1. Rayleigh-scatter system. Applied Optics 34 (30) 6925-6936, 1995.
• Environment Canada: Air Quality Processes Research Division [Online]. http://www.msc.ec.gc.ca/arqp/index_e.cfm [Nov. 24, 2005].
• Purple Crow Lidar [Online]. http://pcl.physics.uwo.ca/ [Nov. 24, 2005].• REALM: Regional East Atmospheric Lidar Mesonet [Online]. http://
alg.umbc.edu/REALM/ [Nov. 24, 2005].• The Atmospheric Optics Laboratory [Online]. http://aolab.phys.dal.ca [Nov.
24, 2005].