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TRANSCRIPT
Canadian Hydrographic Conference 2020
Adopting a modern approach to
compiling bathymetry for nautical
charts
Gabriel Cavanagh & Julie LarrivéeCanadian Hydrographic Service
Karen CoveTeledyne CARIS
Soundings
• Describe the sea bottom
• A subset of the known depths
• Carefully picked• Accuracy
• Safety
• Legibility
Selecting soundings
• Mostly a manual operation
• A subjective process
• Complex
• Time consuming
• Prone to errors
CHS Transformation
• High demand for products and services
• Growing portfolio of ENC
• Adopt IHO standards
• Improved data collection capacity
• Efficiency is needed
A good sounding selection...
• Shows the general configuration
of the sea bottom
• Shows the dangers to navigation
• Shows the available water
column
• Answers the needs of the
mariners
IHO Charts Specifications (S-4)
• The least depth over shoals should be shown.
• The density of the soundings should be determined by the type of seabed.
• The soundings and depth-contours must complement each other.
• The shoalest depth should be shown in critical areas.
• […]
• No measured depth should be shoaler than the interpolation made from the soundings and depth contours on the chart.
IHO Charts Specifications (S-4)
• The least depth over shoals should be shown.
• The density of the soundings should be determined by the type of seabed.
• The soundings and depth-contours must complement each other.
• The shoalest depth should be shown in critical areas.
• […]
• No measured depth should be shoaler than the interpolation made from the soundings and depth contours on the chart.
IHO Charts Specifications (S-4)
• The least depth over shoals should be shown.
• The density of the soundings should be determined by the type of seabed.
• The soundings and depth-contours must complement each other.
• The shoalest depth should be shown in critical areas.
• […]
• No measured depth should be shoaler than the interpolation made from the soundings and depth contours on the chart.
IHO Charts Specifications (S-4)
• The least depth over shoals should be shown.
• The density of the soundings should be determined by the type of seabed.
• The soundings and depth-contours must complement each other.
• The shoalest depth should be shown in critical areas.
• […]
• No measured depth should be shoaler than the interpolation made from the soundings and depth contours on the chart.
IHO Charts Specifications (S-4)
• The least depth over shoals should be shown.
• The density of the soundings should be determined by the type of seabed.
• The soundings and depth-contours must complement each other.
• The shoalest depth should be shown in critical areas.
• […]
• No measured depth should be shoaler than the interpolation made from the soundings and depth contours on the chart.
A good sounding selection...
• Is not a simple generalization of
the known depths.
• Uses the chart features as
guides and constraints.
Commercial solutions
• Shoal-bias sounding selection
using a suppression radius• Selects the shoalest soundings
• Suppress the surrounding
soundings
• Selects the next shoalest
soundings
• Suppress the surrounding
soundings
• Until all soundings are classified
• Requires the cartographer’s
intervention
Commercial solutions
• Shoal-bias sounding selection
using a suppression radius• Selects the shoalest soundings• Suppress the surrounding
soundings
• Selects the next shoalest
soundings
• Suppress the surrounding
soundings
• Until all soundings are classified
• Requires the cartographer’s
intervention
Commercial solutions
• Shoal-bias sounding selection
using a suppression radius• Selects the shoalest soundings
• Suppress the surrounding
soundings• Selects the next shoalest
soundings
• Suppress the surrounding
soundings
• Until all soundings are classified
• Requires the cartographer’s
intervention
Commercial solutions
• Shoal-bias sounding selection
using a suppression radius• Selects the shoalest soundings
• Suppress the surrounding
soundings
• Selects the next shoalest
soundings• Suppress the surrounding
soundings
• Until all soundings are classified
• Requires the cartographer’s
intervention
Commercial solutions
• Shoal-bias sounding selection
using a suppression radius• Selects the shoalest soundings
• Suppress the surrounding
soundings
• Selects the next shoalest
soundings
• Suppress the surrounding
soundings• Until all soundings are classified
• Requires the cartographer’s
intervention
Commercial solutions
• Shoal-bias sounding selection
using a suppression radius• Selects the shoalest soundings
• Suppress the surrounding
soundings
• Selects the next shoalest
soundings
• Suppress the surrounding
soundings
• Until all soundings are classified
• Requires the cartographer’s
intervention
Collaborative development
• Enhancement of the Sounding
Selection tools inside CARIS
Base Editor.• Provides an automatic workflow
• Meets S-4 specifications
• Allows manual interventions
Finding the right approach
• Review of CHS criteria:
– Must allow for automated, semi-automated workflows
– Must allow for human intervention, manual workflows
– Must conform to specifications
• And for a CARIS COTS solution
– Must be scalable
– Must be performant
– Must be consistent (reproducible)
– Must be flexible to support workflows of many customers
Finding the right approach
• Cartographer defined rules based hierarchy to apply
• Machine classifies data points to include or suppress
• Machine validates results and guides user interactions
• Cartographer supervises and overrides decisions (if needed)
• Maintains machine and user assigned attribution for full traceability
THIN POINTSEXPORT TO SOUNDING FEATURES
Point cloud or Surface
Classification cloud
CLASSIFY POINTS
(automatic)
CLASSIFY POINTS
(manual)
CARIS takes a new approach
• Allows input of:– Generalized contours
– Charted features
– Surface models
• Automatic classification:– Selected by rule
– Suppressed by rule
• Manual classification
• Cartographer as supervisor
The rules
• Suppress within area
• Suppress deeper than elevation
• Suppress using threshold
• Select in isolated contours
• Select critical uncontoured shoals
• Select significant soundings to complement existing bathymetry
• Select background soundings
• Select/Suppress based on proximity to features
Conclusion
• CHS Transformation to address challenges
• CHS and CARIS motivated to define a new way to compile bathymetry
• A new approach using classification and cartographer as supervisor
• Workflows can be automated or semi-automated
• Goal of project is to develop software tools and cartographic results
that meet both CHS and CARIS’ criteria