LiDAR Range (R) recorded as R = c * t/2 Unaffected by clouds above c= speed of light t = time for signal to send and return Unaffected by clouds above 100,000 pulses of light / second Data are generated as a ‘cloud’ of millions of points

Early systems recorded only the first return System threshold separates a real return from noise

LiDAR Can create: 1. High resolution DEMs: - 10cm Open gentle terrain - 50cm Forested or steep terrain 2. Vegetation layers The only RS device to record multiple layers Can record bare earth and/or vegetation layers LiDAR is mostly airborne but some spaceborne

Applications Detailed topographic mapping Coastal areas – change / flooding Linear disturbance – pipelines, power lines Geological fault lines Landslides Forestry – biomass, canopy height, leaf area Bathymetric – depth and surface layer biomass 3D urban mapping Glacier elevation and change Atmospheric – clouds, gases Most common wavelength:    1064 nm (Near IR) Bathymetric surveys: 532 nm (green)   

LiDAR – 1064 nm, 532nm, 355nm - why those wavelengths ? (Not solved by google or LiDAR marketing companies) Lasers produce light the same way as a neon sign – a substance is stimulated to an excited state, causing the release of extra energy as a photon of light. Nd:YAG (neodymium-doped yttrium aluminium garnet) is a crystal that is used as a lasing medium for solid-state lasers. It emits at a wavelength of 1064 nm. According to the Planck-Einstein equation: Where h= Planck’s constant, and c = the speed of light, halving the wavelength, has the effect of doubling the energy released, and one-third the wavelength (355) triples the energy (= the second and third harmonics) Solved by Patrick Daley, GEOG432

Layers in the data cloud N.Coops, UBC

DEMs: Bare Earth and Canopy

San Andreas Fault zone

TRIM versus LiDAR

LiDAR – ice surfaces http://gsc.nrcan.gc.ca/glaciology/national/activities_e.php

UNBC area

University Hill

LiDAR vegetation data in 3D: ALRF 500m x 500m ~ 1,000,000 points

Raw Point Files For individual tree analysis (FUSION/LDV) Elevation of lowest point 675.21m ASL Elevation of highest point 707.87m ASL Tree Height ~ 32.66m Crown Shape ~ Convex (umbrella) Crown Footprint ~ 11.55m These points can be used in analysis directly In this image I’ve zoomed into the points that describe a riverside tree

Canopy Height = Canopy Surface – Bare Earth Canopy Surface Model Each cell in a canopy surface model details the elevation of the highest feature within that cell Height is more practical than elevation for describing vegetation Canopy Height = Canopy Surface – Bare Earth

Canopy Surface Model

Canopy Height Model

Canopy Surface Model

Stand Level Vertical Return Density Schematic of a 20m x 20m LiDAR Point Cloud – 400 Pulses Histogram of Returns (percent)

Stand Level Vertical Return Density Schematic of a 20m x 20m LiDAR Point Cloud – 400 Pulses Histogram of Returns (percent)

Stand Level Vertical Return Density Schematic of a 20m x 20m LiDAR Point Cloud – 400 Pulses Histogram of Returns (percent)

Tree Stem Maps Individual tree crowns are discernable from the Canopy Height Model so we developed a tree finding algorithm to identify tree stem locations

Tree Stems (displayed by tree height)

LiDAR Data (by crown size) Vegetation Data Products LiDAR Data (by crown size)

Tree Stems (displayed by crown shape)

http://www-lite. larc. nasa. gov/n_the_images http://www-lite.larc.nasa.gov/n_the_images.html LITE: Lidar In-space Technology Experiment Sept 1994

ICESat (Ice, Cloud,and land Elevation Satellite) 2003-2009 GLAS (Geoscience Laser Altimeter System) is the first laser-ranging (lidar) instrument for continuous observations of Earth Orbits at 600km at 94 degree angle (covers 86N – 86S), lasers: infrared light (1064 nanometers) for topography and dense clouds visible green light (532 nanometers) for clouds and aerosols Laser pulses illuminate spots (footprints) 70 metres in diameter, spaced at 170-metre intervals along Earth's surface.

Greenland

Antarctica - IceSat

Amazon - IceSat

IceSAT vegetation

Mars Orbiter Laser Altimeter (MOLA) -on the Mars Global Surveyor spacecraft. It collected altimetry data about the height of surface features on Mars from 1996- 2001. Data collected at 1064 nm – Vertical res. 37cm (~1 foot) This is a pole-to-pole view of Martian topography from the first MOLA global topographic model. The slice runs from the north pole (left) to the south pole (right) along the 0° longitude line. The south pole has a higher elevation than the north pole by ~6 km. This global-scale slope controlled the surface and subsurface transport of water indicated by outflow channels and valley networks. Discoveries e.g seasonal snow: http://mola.gsfc.nasa.gov/discoveries.html

MOLA images http://mola.gsfc.nasa.gov/images.html