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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