An ENC will be presented, together with its updates, in a SENC (System Electronic Navigational Charts).
The methodology for presenting ENC data for voyage planning or for the voyage on the screen is not explicitly defined in IMO Performance Standards for ECDIS, and each ECDIS manufacturer will deal with this in different ways.
Two different approaches, discussed in more detail, follow:
Vector chart presentation will not deteriorate if the mariner selects a scale for which the Usage Band was not defined. The chart information presented will only be the optimum available for the current Usage Band selected; this may not be to the level of accuracy required. Therefore a warning system must be in place to inform the mariner when the wrong scale for a Usage Band is selected.
In that case, as requested by the IMO Performance Standards for ECDIS, highlight over-scale patterns or other indications to show the use of wrong scales have to be presented.
The figures display options to indicate incorrect usage of scale ranges.
The different own ship presentation for both scales has been defined in the S52 standard and will be generated automatically by the system.
"Note that if the display is compiled from more than one ENC of the same compilation scale, and if the mariner deliberately chooses to zoom in so that the display scale exceeds the compilation scale, then only the "overscale indication" should be shown. The"overscale pattern" AP(OVERSC01) should not be shown."
((S52 PresLib Edition 3.4 part I Chapter 12.2.2)