passive and active: remote survey solutions for the … · remote survey solutions for the...
TRANSCRIPT
www.fugro.comwww.fugro.com1
PASSIVE AND ACTIVE: REMOTE SURVEY SOLUTIONS FOR THE NEARSHORE
An Integrated Approach Featuring Remote Sensing, ALB and Acoustic Techniques
Don VenturaFugro Pelagos, Inc.Coastal GeoTools 2017, North Charleston, SCFebruary 2017
www.fugro.comwww.fugro.com2
Introduction
Photos: http://www.shedexpedition.com/wp-content/uploads/2014/04/Virginia-Beach-sky-view.jpg; http://gpmoorephoto.com/blog/wp-content/uploads/2012/11/Icy-Bay-Mount-Saint-Elias-Alaska-Photo.jpg;
• Emphasis on nearshore surveys and the coastal hinterland has increased over the past few years.
• Generated by concerns over various issues, including:
• sea level rise due to climate change • directly-attributable man-made issues such as
land subsidence through extraction of valuable mineral and water resources;
• growth of, and reliance on, a seaborne Blue Economy delivering goods as efficiently as possible;
• concerns over erosion or damage to nearshore ecosystems necessitating additional focus on habitat mapping and environmental surveys in general
• an increasing percentage of the world’s human population residing in close proximity to the coast which places extra emphasis monitoring of this margin
www.fugro.comwww.fugro.com3
Nearshore Mapping
• Where possible, the most cost effective approaches to mapping nearshore, high-impact coastlines – notwithstanding absolute accuracy standards - are:
• Remote sensing from wide-area satellite imagery ($)• Satellite Derived Bathymetry – SDB• Multispectral Imagery• Satellite Altimetry
• Airborne active sensor techniques ($$)• High-resolution RGB Photography• Hyperspectral Imagery• Topographic Lidar• Topo-Bathymetric Lidar• Bathymetric Lidar
• Traditional acoustic hydrographic survey techniques ($$$)• MBES, SBES, SSS etc.
• All of the above are affected in different ways by metocean conditions in the nearshore environment: water clarity, seabed colour and rugosity, platform dynamics and operational parameter windows etc.
www.fugro.com4
Remote Sensing Techniques (Geospatial)
Low Altitude Corridor LiDAR
(Helicopter)
High Altitude Photogrammetry
Low High
Low
HIg
h
Accuracy
Altit
ude Medium Altitude
LiDAR
Airborne Bathymetric
LiDAR
Satellite Imagery
Mobile / Terrestrial Laser
ScanningSonar
Bathymetric Survey
High Altitude SAR (Radar)
www.fugro.comwww.fugro.com5
Satellite Derived Bathymetry (SDB) and Imagery
www.fugro.comwww.fugro.com6
Approaches to use optical satellite imagery
Indicative / empirical methods:
Relate brightness and log-ratios to water depth
Photogrammetric / stereo approach:
Find matching points on seafloor
Physics based multispectral approach:
Resolve light-transfer and retrieve optical properties
Source: DigitalGlobe WorldView-2, acquisition date: 2011-10-30
www.fugro.comwww.fugro.com7
Physics-Based Approach: Overview
Image courtesy of the Centre for Spatial Environmental Research, University of Queensland
Schema of the light signal measured by optical satellites
Physical realization of the system
www.fugro.comwww.fugro.com8
Raw Satellite Imagery: Heron Island WV2
Includes copyrighted material of DigitalGlobe. WorldView-2, acquisition date: 2011-10-30
www.fugro.comwww.fugro.com9
Atmospheric Effects Removed
Includes copyrighted material of DigitalGlobe. WorldView-2, acquisition date: 2011-10-30
www.fugro.comwww.fugro.com10
Water Column Removed
Includes copyrighted material of DigitalGlobe. WorldView-2, acquisition date: 2011-10-30
www.fugro.comwww.fugro.com11
SDB Process Example: Antigua – ‘Raw Image’
Correction applied: Atmosphere andadjacency
Water surface effects
Water column
Provides general information, but typically not well suited for aquatic and benthic analysis
Antigua
Northeast Antigua
www.fugro.comwww.fugro.com12
SDB Process Example: Antigua – SubSurface Reflectance
Correction applied: Atmosphere andadjacency
Water surface effects
Water column
Antigua
Provides more detailed information on geomorphologic zoning, spatial and spectral patterns of the seafloor and benthic habitats.
Sat. data used: Moderate res. (15m grid)
Northeast Antigua
www.fugro.comwww.fugro.com13
SDB Process Example: Antigua – Seafloor Reflectance
Correction applied: Atmosphere andadjacency
Water surface effects
Water column
Antigua
Sat. data used: Moderate res. (15m grid)
Northeast Antigua
Provides very detailed information on geomorphologic zoning, spatial and spectral patterns of the seafloor and benthic habitats. It represent a clear view to the surface being corrected for water column effects and a perfect baseline for benthic habitat mapping.
www.fugro.comwww.fugro.com14
SDB Process Example: Antigua – Satellite Derived Bathymetry
Correction applied: Atmosphere andadjacency
Water surface effects
Water column
Sat. data used: Moderate res. (15m grid)
Provides bathymetric information in a dense grid. Data are mapped using EOMAP’s physics based inversion algorithms, which has been applied in more than 40 areas worldwide.
Antigua
Northeast Antigua
www.fugro.comwww.fugro.com15
Can we trust the cheapest option?
We can, if we apply an integrated approach….• SDB can provide very effective cost-effective and initial coverage of a suitable, clear-
water nearshore area• We can take the initial results and do at least three things:
• Use the data to provide reconnaissance information for follow-on, more easily quantifiable survey techniques (put an otherwise poorly charted area in focus)
• Conduct more discrete, higher-resolution surveys of the most critical areas for development or coastal defence/monitoring
• Use the active sensor data to refine the original SDB results to create a better-defined, integrated product which can start to attain accuracies acceptable to a wider stakeholder group
• We can also start to recognize the benefits of well-developed algorithms of satellite imagery to extract even more habitat info from the coastal zone.
www.fugro.comwww.fugro.com16
Airborne Lidar Bathymetry (ALB)
www.fugro.comwww.fugro.com17
Accurate depth measurement Very cost effective over full operational window Speed Mobility Rapid response Rapid data assessment: storm damage, grounding, seasonal change Completion of surveys in small environmental windows Survey in difficult or impossible areas for vessels Safe in dangerous areas Simultaneously survey water, structures, and land
What’s the overall benefit of ALB?
www.fugro.com18
Closing the Gap with ALB
www.fugro.comwww.fugro.com19
North Jeddah – Chart Comparison
Merged with deeper MBES data in the channels, the overall effect provides a seamless land-water interface
www.fugro.comwww.fugro.com20
Point Clouds and Surfaces
• Many of the biggest changes seen during ALB surfaces are often at the coastline itself.
• Wholesale changes in topography and land usage are not uncommon
www.fugro.comwww.fugro.com21
RGB Imagery
• Aerial imagery is a hugely useful tool in ALB surveys
• Object detection and classification
• Confirmation of specific high points in the Lidar point cloud
• Source data for ortho-rectified mosaic products
• Good for hydrographic notes – instant proof!
www.fugro.com22
Bare Earth Surface Elevation Model (DEM)
www.fugro.com23
Intensity/Backscatter Raster Imagery
www.fugro.comwww.fugro.com24
Applications: Eelgrass Mapping
• Boundary maps for eelgrass and aquaculture farms.
• Density counts and maps of aquaculture farming.
• Hydrographic chart data for navigation and aquaculture farming.
• Baseline for change detection.
Image courtesy of Tim Webster, COGS
www.fugro.comwww.fugro.com25
Florida PanhandlePost Hurricane Ivan 2004
Applications: Imagery Fusion for Habitat Mapping
www.fugro.comwww.fugro.com26
Hi-Res Infrastructure and Coastal Surveys(Integration of Laser and MBES Acoustic Techniques)
Fugro-EOMAP SDB Webinar – 10/11 May 2016
www.fugro.com27
BOAT-MAP™
www.fugro.com28
By incorporating mobile laser scanning into our near shore marine surveying services, Fugro brings BOAT-MAP™ a specialized solution for nearshore marine surveys that need to span the waterline.
BOAT-MAP™
www.fugro.comwww.fugro.com29
Erosion Zones: Averaged Annual Cliff Retreat (cm/year)
Santa Barbara, California – Annual Retreat (cm) & Estimated Cliff Migration
Applications: Track Changes: Coastal Retreat
www.fugro.com30
Port of Los Angeles – Integrated MBES and LLS
Piles Beneath Wharf
www.fugro.comwww.fugro.com31
Port Infrastructure: Sand Spit Napoleonic Fort, UK
www.fugro.comwww.fugro.com32
Summary
• Alternative solutions to the nearshore mapping of many areas are feasible• They will not always attain navigational charting standards• They don’t need to for non-charting agencies• We need to have an open mind as to how we better serve a greater stakeholder group• There are ways and means of improving initial results from SDB with iterative processes
utilizing ALB full waveform algorithms and a GT approach• There are ways and means of improving final coverage and data density which agrees
within a reasonable tolerance for the benefit of many clients• Key is to quantify what we have and apply appropriate risk to the data usage
www.fugro.com
Thank You