May 8, 2013 Small Footprint Topo-Bathymetric LiDAR PNAMP Remote Sensing Forum Russ Faux, Co-CEO, WSI Amar Nayegandhi, Manager of Elevation Technologies, Dewberry Colin Cooper, Senior Analyst, WSI
Watershed Sciences Mapping: Light Detection and Ranging (LiDAR) Thermal Infrared Imagery Digital Multi-Spectral Imagery Bathymetric/Sonar Geodetic Survey Analysis: Water Quality Modeling Automated Feature Extraction Forest Inventory and Vegetation Analysis Fish and Wildlife Habitat Assessments Spatial Data Analysis and Visualization Utilities and Infrastructure Mapping
Topobathymetric LiDAR pilot study Riegl VQ-820-G Sandy River, Oregon (DOGAMI, BLM, FEMA) Snake River, Idaho Lake Kabetogama, MN Toutle River, WA Bridge Creek, OR Lake Kabetogama 1m x-section
Why Topobathymetric LiDAR? Airborne topobathy LiDAR is of high value in filling the 0 to 10 m depth gap in coastal and riverine areas Rapid survey of shallow water areas that are difficult, dangerous, or impossible to get using water borne methods River and estuary environments: channel cross sections, water level dynamics, biological habitat, riparian conditions Image courtesy Optech, Inc.
Traditional bathymetric LiDAR operating principles
Analyzing Bathymetry Waveforms Transmit waveform ~1.5 ns FWHM Water Surface return Return waveform Bottom return 16 ns (~1.8 m depth)
Sensor Installation Mounted in a WSI Cessna Caravan with Leica ALS60 and RCD camera for co-acquisition
Calibration Flight - Osborne Waterpark, Corvallis, OR
Sandy River, OR Project Funding from DOGAMI, FEMA, & BLM. 43-miles of river corridor. Home to Chinook, Coho, and Steelhead 2007 Removal of the Marmot Dam.
Survey Conditions Low flow, maximum water clarity. Secchi depth = 2.1 meters measured at Oxbow Park.
Acquisition Parameters LiDAR Survey Settings & Specifications Sensor Riegl VQ820G Leica ALS60 Survey Altitude (AGL) 600 m 600 m Target Pulse Rate 130 khz 135 khz Laser Wave Length 532nm 1064 nm Laser Pulse Diameter 60cm 15 cm Scan Pattern Elliptical Sinusoidal Field of View 40, 20 forward fixed angle 40⁰ GPS Baselines 13 nm 13 nm GPS PDOP 3.0 3.0 GPS Satellite Constellation 6 6 Maximum Returns unlimited 4 Intensity 16-bit 8-bit Full Waveform Yes No Resolution/Density 4-5 pulses/m 2 Average 8 pulses/m 2
Channel Cross Sections 86 cross sections @ 100 meters
Comparing with Channel Cross Sections
Comparing with Channel Cross Sections
Comparing with cross-sections 1 Distance along transect (m) Distance along transect (m) Elevation (m) Elevation (m) Elevation (m) Elevation (m) 6 1 2 3 4 5 6 2 3 4 5 15 Powerpoint title goes here December 20, 2011 Distance along transect (m)
Surface Conditions
Accuracy Bare Earth (Topo) Absolute Accuracy (Hard Surface RTK points) High Confidence Bathymetric Accuracy (In Channel Points) Low Confidence Bathymetric Accuracy (In Channel Points) Sample 164 303 28 Average <0.001-0.051-0.150 Median 0.004-0.058-0.248 RMSE 0.030 0.184 0.418 1σ 0.030 0.177 0.397 1.96σ 0.060 0.347 0.779
Depth Penetration Cover Classification % of total area Point Density High Confidence 83% 1.96 points/m 2 Low Confidence 17% 0.11 points/m 2
Depth Penetration
Bathymetric Point Classification Classification Classification Number Name 1 Default 2 Ground 19 Channel Bottom 20 Water Surface 24 Water Column Classification Description Laser returns that are not included in the ground classification. Ground that is determined by a number of automated and manual cleaning algorithms to determine the best ground model the data can support. Ground points that fall within the water s edge breakline which characterize the submerged topography. Default points that fall within the water s edge breakline which characterize the surface of the water. Any remaining points within the water s edge breakline that do not represent the water surface or bathymetry.
1 meter cross section of the Green River, upstream of the confluence with the North Fork Toutle River. A Green LiDAR NIR LiDAR B Depth = 2.3 meters
Subtraction model accentuates the active channels.
Multi-Spectral LiDAR The 3D Images represent a 10 meter cross-section of an group of trees near the junction of Nestucca River Rd and NW Meadow Lake Rd in the Panther Creek Experimental Forest
Summary Small-footprint topobathymetric LiDAR systems have arrived in the commercial industry! How deep can your sensor go it DEPENDS! The Riegl VQ-820-G has produced very encouraging results in mapping shallow submerged topography. Accuracy results comparable to traditional NIR LiDAR, but also difficult to assess using conventional cross sections. The NIR LiDAR proved invaluable for computing refraction. Advanced processing methods still under development for identifying false bottom returns and areas of low confidence. This technology has several applications including: Floodplain Mapping Fisheries management Marine resource and coral reef management Storm surge modeling and storm damage assessment Rapid shoreline assessment
Thank you! For additional information, please contact us. Russ Faux WSI Corvallis, OR PH: 541-752-1204 FX: 541-752-3770 E: faux@wsidata.com