SATELLITE DERIVED BATHYMETRY (SDB): NEW METHODOLOGY … · • Emphasis on nearshore surveys and the coastal hinterland has increased over the past few years. • Generated by concerns

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SATELLITE DERIVED

BATHYMETRY (SDB):

NEW METHODOLOGY

TO HELP ADDRESS

THE NEARSHORE

BATHYMETRY DATA

GAP FOR ALASKA

Don Ventura

Fugro Pelagos, Inc.ASMC GeoJam 2017,

Anchorage, AK

February 2017


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


Introduction

At the same time….

• Economic pressures bring the need for cost-

effective methods of garnering geospatial

data in the nearshore

• Mapping of the land-sea interface requires

the adoption of a broader approach to

hydrographic surveying techniques and

technologies

• This presentation will discuss a solution to

this issue through the pragmatic use of

satellite derived bathymetry techniques in a

real-world scenario from Alaska.

The Importance of Hydrography

why is hydrography important?


A dilemma….

• Much of the growth in resource exploitation within close proximity to the coast happens in

poorly developed countries with little infrastructure or in remote, resource-rich regions such as

Alaska

• We as an industry are an expensive data collection option for many of these countries and

regions

• Their lack of adequate charting becomes more acute as the global economy matures,

marginalizing them even more

• We need a different approach to lower the first rung on the geospatial data acquisition ladder


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.

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Remote Sensing Techniques (Geospatial)

Low Altitude

Corridor LiDAR

(Helicopter)

High Altitude

Photogrammetry

Low High

Low

HIg

h

Accuracy

Altitude Medium Altitude

LiDAR

Airborne

Bathymetric

LiDAR

Satellite

Imagery

Mobile /

Terrestrial Laser

ScanningSonar

Bathymetric Survey

High Altitude

SAR (Radar)


Satellite Derived Bathymetry (SDB) and Imagery


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


Physics-Based Approach: Overview

Image courtesy of the Centre for Spatial Environmental Research, University of Queensland

Schema of the light signal

measured by optical satellitesPhysical realization of the

system


Raw Satellite Imagery: Heron Island WV2

Includes copyrighted material of DigitalGlobe. WorldView-2, acquisition date: 2011-10-30


Atmospheric Effects Removed



Water Column Removed



Atmospheric Effects Removed (Pre-Correction)



Atmospheric Effects Removed (Post Correction)



Atmospheric scattering from adjacent land areas

Requirements for identification, correction of adjacency effect


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


SDB Process Example: Antigua – SubSurface Reflectance

Correction applied:



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


SDB Process Example: Antigua – Seafloor Reflectance

Correction applied:



Water column

Antigua

Sat. data used:


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.


SDB Process Example: Antigua – Satellite Derived Bathymetry

Correction applied:



Water column

Sat. data used:


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


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.


Seafloor Reflectance over Bathymetric Data



Assessing the Utility of SDB


Application: Coastal Zone Management

Worldbank-ESA Integrated Coastal Zone Management: SBD for Palk Bay, India


Application: Nautical Charting

EOMAPs SDB product competed against three other methods from other service providers

and was used in the BA2066 chart, the first UKHO chart which includes SDB data.

See also the UKHO session at the shallow water conference 2015:http://www.shallowsurvey2015.org/presentations/SS2015_Session05_Talk1_UKHO.pdf


Client: Qatar Shell GTL limited

Challenge: Fast bathymetry survey to support seismic programs 740 sqkm offshore area

to be mapped within 2 weeks.

Solution and benefits:

o EOMAP physics based processing using Worldview-2 satellite data, generating a

large area bathymetry map with excellent agreement to a multi-beam data set, which

was limited to a single, localized area

Significant cost savings > $1M

Project schedule efficiently supported

HSE risks mitigated

Recognized as key technology to aid

the planning and preparation

of seismic surveys

Applications: Shell Qatar Seismic Survey Support

740 sqkm Qatar shallow water bathymetry survey, 2010.doi:10.2523/17346-MS https://www.onepetro.org/conference-paper/IPTC-17346-MS‘Supporting Qatar Shell with the execution of onshore and offshore seismic programs’ , IPTC conference 2014


Application: Legal Evidence

South China Sea: Den Haag court case

Using Very High resolution Satellite Images for Den Haag court case


Application: Seafloor Baseline and Monitoring

Clients: Environmental Agency Abu Dhabi EAD, CONABIO Mexico, Australia Ningaloo, ..

Challenge: Regulatory requirement to update the coastal habitat mapLarge and remote submerged area to be covered in high-resolution.

Solution and benefits:

o Harmonized data processing on seafloor properties using multiple satellites

o Robust and consistent measures and maps through EOMAP technologies

Fast delivery, no HSE risks, largely independent on in situ measures

Cost effective, outstanding resolution

“The mapping ..of the project has met our expectations, and we have already begun to use the delivered data in our day-to-day operations”Anil Kumar, Director, Environment Information Management, EAD

EAD database: http://enviroportal.ead.ae/mapviewer37 000 sqkm, layers produced by EOMAP 2013/2014


Application: Alaska

Arctic Domain Awareness Center

Proposal To Address The Shortfall In Nearshore Bathymetry

Addressing the Arctic Domain Awareness Center (ADAC)’s

Request for Proposal – Sept 2016


Which issues were we trying to address?

• We focussed mainly on Question 3 of the RFP under category: “Mitigating Arctic

Environmental Hazards”, specifically:

• “How can we improve awareness and understanding of nearshore bathymetry

across the Arctic (in particular, the North American Arctic)?”

• In doing so, another question posed in the RFP was also partially addressed:

• “How can “on-demand” “local/localized” domain awareness be achieved (via user

defined parameters) and what kind of technologies can best support localized

domain awareness in austere Arctic environments?”


Goals and Objectives

The Goal of this proposal is to deliver a cost-effective, modern and up-scaleable approach

to improving awareness and understanding of nearshore bathymetry focused on the Alaska

Arctic coast. The SDB feasibility study will address the following objectives:

Definition and accurate determination of Alaska Arctic coast’s environmental suitability to

extract bathymetry from satellite;

Definition of bathymetric data specifications and areas of interest by key stakeholders

relying on nearshore arctic bathymetry for management decisions;

Raising awareness of SDB and Satellite derived habitat characterization as an alternative

method for nearshore bathymetric data collection, its reliability and cost effectiveness as

compared with active sensor methods;

Processing of suitable–for-SDB data and development of SDB deliverables to requested

data spec, thereby reducing bathymetric data gap;

Assess usefulness and value of generated SDB results in improving understanding of

nearshore bathymetry.


Extent of the AOI

The area of coverage obtainable with contemporary (operational) satellite technology is

shown in red below:


Extent of the Available Lo-Cost Imagery

Approximately 148 scene footprints in blue result in approx. 450-1000 cloud and ice free

Landsat 8 scenes to be analysed


Possible Satellite Derived Data Outputs

High Resolution Satellite Derived Bathymetry

o Bathymetry data (32bit floating GeoTIFF, ASCII XYZ file);o Metadata (XML);o Map (PDF);o On request: Fledermaus SD file, KMZ file, contour lines, etc.

High Resolution Seafloor Habitat Mapping

o Seafloor habitat classification (ESRI polygon shapefile), including relevant attributes;o Subsurface reflectance data (GeoTIFF);o Metadata (XML);o Map (PDF).

Land Cover Mapping

o Land use classification (ESRI polygon shapefile), including relevant attributes;o Subsurface reflectance data (GeoTIFF);o Metadata (XML);o Map (PDF).

Raw satellite Imagery Data for the aboveo Satellite image data: GeoTIFF and metadata.


Tasks and Deliverables

1. Data feasible for SDB processing along the Alaska Arctic to include:

• Multi-temporal satellite image analysis of Landsat 8 and Sentinel 2a raw data;

• Identification and mapping of optically shallow water (approx. SDB area);

• Vector polygon shape of the approximate feasible SDB area (based on Landsat

and Sentinel);

• Vector polyline shape of the coastline (based on Landsat and Sentinel).

2. Stakeholder outreach

• Stakeholder specific SDB processing plan;

• Stakeholder outreach report;

• Unit cost analyses of SDB vs. other data acquisition methods for developed plans.

3. Processed SDB data deliverables - Optional

• Bathymetric grid, 15m and/or 10m spacing stored as ASCII XYZ and/or GeoTIFF

including metadata;

• Vector polygon shape of obstruction not identified in the bathymetric dataset.

4. SDB Results Survey and final report


Project Impact/Benefit

• Risk reduction for on-site responders;

• Improved intelligence for possible ports of refuge and or grounding locations for

distressed vessels;

• Improved intelligence to support management decisions;

• A powerful bathymetric reconnaissance tool to better focus limited time and resources to

collect active sensor data;

• Increased confidence in a more complete and up-to-date coastal bathymetry dataset;

• Advancement of “on-demand” bathymetry concept that could result in a game-changing

approach to collect nearshore bathymetry in challenging environment.


Project Impact/Benefit

The impact and benefit of a regional, holistic, nearshore bathymetric dataset with additional

information on seabed composition and habitat characterization for generally un-surveyed

or poorly surveyed swathes of the Alaskan coastline can assist the following agencies and

institutions with:

• marine rescue,

• navigation safety,

• resource management,

• coastal infrastructure management,

• climate adaptation and resilience,

• economic investment,

…and habitat protection responsibilities all stand to benefit from this baseline data.


Programmatic Risks and Mitigation Plans

• This is a low-risk, high-reward opportunity.

• The ability to analyse 125,000 km of Alaska coastline to

improve understanding of nearshore bathymetry for the

proposed price is unprecedented.

• There is a risk that SDB results may not generate data

quality levels specified by the stakeholder.

• That in itself is also a valuable result that would further

improve the state of practice of using SDB as a viable

method to augment other tried and true, but more

expensive active sensor bathymetry acquisition methods.

• Negative results can be used to specify where further

data acquisition with active sensors is the right way to go.

• Known spring thaws and other environmental factors

affecting water clarity will be taken into account when

selecting satellite imagery.


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

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Thank You

Documents

SATELLITE DERIVED BATHYMETRY (SDB): NEW METHODOLOGY … · • Emphasis on nearshore surveys and the coastal hinterland has increased over the past few years. • Generated by concerns