Rock Talk: RNC to ENC

In a recent note (Rock Talk—Is it all awash, or not?) we discussed minor conflicts in paper-chart rock symbol terminology for a rock that covers and uncovers, height unknown (US supplemental symbol Ka and INT 1 symbol K11). One of the virtues of moving onto electronic navigational charts (ENC) is we no longer rely on the design of the symbol to convey specific information, and instead we get this from a direct query of the ENC database. This database uses an internationally accepted terminology that overrides national nuances.
Below is a summary of common paper-chart rock symbols with a graphic presentation of their relative soundings.
Figure 1. Common rock symbols used on paper charts and RNCs.

Figure 1. Common rock symbols used on paper charts and RNCs.

ENC charts, however, have simplified the actual symbols, not just for rocks, but also for other objects traditionally shown on paper charts. Part of this difference is schematically shown in Figure 2. Going forward, we can abbreviate “paper charts” with RNC (Raster Navigational Charts), because that form of an electronic chart is just an image of the actual paper chart.  The figure caption also refers to INT 1, which is the International Hydrographic Organization (IHO) standard for paper chart symbols.

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