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ECDIS “DUAL-FUELLING”

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Because of the complex and involved nature of ENCs,

it will take some time to provide complete coverage for the world.

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There is therefore a secondary mode of operation called Raster Chart Display System (RCDS) being proposed for ECDIS.

This is sometimes referred to as ECDIS “duel fuelling”.

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“Dual Fuelling” is the ability to use official raster charts, such as Seafarer or ARCS in ECDIS equipment for those areas where authorised vector charts (ENC’s) do not exist yet.

Using official raster charts in ECDIS equipment can provide some, but not all of the functions of ECDIS.

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Differences Between RCDS and ECDIS

Raster data, itself, will not trigger automatic alarms (for example, anti-grounding).

However, some alarms can be generated by raster systems from user-inserted information.

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These can include: clearing lines ship safety contour lines isolated dangers danger areas

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Horizontal datums and chart projections may differ between raster charts.

Mariners should understand how the chart datum relates to the position fixing system.

In some instances, this may appear as a shift in position.

This difference may be most noticeable at grid intersections and during route monitoring.

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Chart features cannot be simplified or removed to suit a particular navigational circumstance or task at hand.

This could affect the superimposition of radar/ARPA targets.

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Without selecting different scale charts, the look-ahead capability may be somewhat limited.

This may lead to some inconvenience when determining range and bearing or the identity of distant objects.

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Orientation of the raster chart display to other than north-up, may affect the readability of chart text and symbols.

It may not be possible to interrogate raster chart features to gain additional information about charted objects.

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It is not possible to display a ship’s safety contour or safety depth and highlight it on the display, unless these features are manually entered during route planning.

Depending on the source of the raster chart, different colours may be used to show similar chart information.

There may also be differences in colours used during day and night time.