Positioning with LiDAR Lucia Scimone, 31 st May 2011 GMAT9205 – Fundamentals of Geo-Positioning School of Surveying and Spatial Information Systems The University of New South Wales Lucia Scimone, 31 st May 2011 GMAT9205 – Fundamentals of Geo-Positioning School of Surveying and Spatial Information Systems The University of New South Wales

Aims What is LiDAR? How it is collected XYZ Positioning What does it look like Limitations

Background Australian Hydrographic Office Why? - Marine Navigation, Charting, Environmental Research, Mining /Exploration Shallow water bathymetry, eg. Greet Barrier Reef Source:

Bathymetric Acquisition Methods Source: (left) (right)

LADS Hydrography Source: Australian Hydrographic Service LIDAR - Light Detection and Ranging. Laser Airborne Depth Sounder (LADS II) fitted in a de Havilland DASH 8 aircraft. Land Based

Lidar Data Collection Source:

LiDAR Data Collection Airborne LiDAR system consisting of lasers, scanner, optics, and acquisition, electronics. Picture: Andreas Axelsson, (2010)” Rapid topographic and bathymetric reconnaissance using airborne LiDAR”, Proc. SPIE, Vol. 7835, Sweden – accessed online at:

“Lasers” L-A-S-E-R : Light Amplification by Stimulated Emission of Radiation two frequency beams – Green laser pulse 532 nm, pulsed (neodymium-doped yttrium aluminum garnet green laser) – Red laser pulse (near infrared beam) 1064 nm Each laser footprint is around 2.5m diameter, green beam passes through water and diverges due to light scattering. Source: Axelsson 2010

Remember last weeks GMAT 9205 Lecture on GPS/INS Integration for Geo-referencing (Week 10)? Positioning Aircraft altitude and speed need to be considered when collecting data: Laser Time return Sampling rate Sub-ns accuracy for timing calibration Beam divergence Target characters

Positioning - xyz Vertical & Horizontal Altitude of aircraft GPS / INS (Inertial Navigation System) Both onboard and at a station on the ground Tides system's operating geometry propagation induced biases wave height Source: ttp://coastalwiki.or g/w/images/8/8b/Li dar_fig_02.jpg

Positioning - xyz The body frame (b-frame) is an orthogonal frame in which the measurements of a navigation system are made. - Origin: The centre of the navigation system - X-axis: Toward the front end of the vehicle - Y-axis: Toward the right side -Z-axis: Downwards and perpendicular to the X-Y plane -(Wang 2011, Lecture 10) The navigation or local level frame (n or l- frame) - Origin: The centre of the navigation system - X-axis: Toward ellipsoidal true north (North) - Y-axis: Toward ellipsoidal east (East) - Z-axis: Downwards direction along the ellipsoidal normal (Down)

Limitations Depth of water < 60m Conditions need to fly <500m so needs good visibility ie. low cloud/ fog present problems Turbidity (refracts light within the water column, produced too much noise) Wind <20knots, sea state

Questions