Notes on S-100 and the Eventual S-101 ENC Display Standard

Background

At present all ENC content and structure (internationally) are based on the IHO S-57 standard, and how these ENC should be displayed is determined by the IHO S-52 standard. ECDIS systems are required to follow the S-52 standard precisely, which does include a few display options, whereas most ECS strive to follow those standards, but they are not required to. Some apps are far from the standard, others, like qtVlm, are remarkably close to the standard.

The change from S-57 to S-101 ENC will be part of a huge change in overall electronic navigation, described as S-100, the Universal Hydrographic Data Model, which includes: 

S-101: Electronic Navigational Charts (ENCs)

S-102: Bathymetric Surface

S-104: Water Level Information

S-111: Surface Currents

S-412: Weather Overlay

Note that the S-100 based product specifications include more parameters than listed here, and indeed their item numbers do not all start S-1xx, as noted in this weather data component. Indeed, the system is intended to encompass all aspects of coastal navigation and hydrography.

 

The new system is much more GIS oriented with various new overlays. Except for the S-101 ENCs themselves, the other components of S-100 are well underway already, with tremendous promise. With digital soundings and tide heights everywhere on the chart, we are then aware of the actual water depths everywhere, which can also be forecasted continuously over time.

So far the S-412 weather products do not add to what racing sailors have been using for years with GRIB formatted model forecasts overlaid on their charts, but this will make the data more universally available to commercial and governmental vessels in the future. Unfortunately, the GRIB format we are all accustomed to, created specifically by the WMO for weather work, will be replaced in S-100 by a new h5 format, that so far none of the popular ECS apps or ECDIS can read! 

Because of the h5 format, it takes extra work to view these new data sets. We have notes on this elsewhere, along with custom conversion apps. 

But the question at hand is the charts themselves and what will govern how they should be displayed, keeping in mind that we are looking ahead, and largely just answering a question that might have come up. S-101 charts are likely to be 5 or so years out, and hopefully by that time the rest of the S-100 suite will be well underway.

Here are notes on the S-101 ENC display standards as presented at the moment.

S-101 absorbs the display standard into itself — it will not be a separate numbered standard.

Unlike the S-57 family (where S-57 = data, S-52 = display, S-58 = validation, S-63 = encryption, as four separate documents), the S-101 ENC Product Specification covers content, structure, data encoding, and metadata for S-101 ENC data, and the same specification also includes the portrayal (display) requirements for use within ECDIS. So portrayal/display rules are baked directly into S-101 as its Portrayal Catalogue, rather than living in a standalone "S-52 equivalent."  The S-101 Portrayal Catalog is analogous to the S-52 Presentation Library.

Conceptually, S-101's portrayal does the same job S-52 does today.

S-101 is similar in content to the current S-57 object catalogue and S-52 presentation library, but implements the dynamic constructs prescribed by the S-100 framework. The key structural difference: in S-101, the relationships between features, attributes, and enumerants are defined in a single feature catalogue, and the portrayal catalogue links those feature catalogue elements to their graphical representation — both built through a machine-readable registry rather than being hard-coded into ECDIS software.

Why this matters practically.

Under S-57/S-52, catalogue updates (new symbols, new display rules) are embedded in ECDIS software and can take up to five years to roll out via software updates, whereas under S-100/S-101 the feature and portrayal catalogues are versioned in a continuously-adapted registry, letting updates happen via catalogue update rather than a full software upgrade cycle. 

There is active work explicitly comparing the two. 

The IHO's S-101 Project Team has a working document titled "Allowable Differences Between S-52 and S-101 Display," and earlier project team materials describe an explicit S-52 to S-101 portrayal gap analysis, along with a list of S-52 symbols no longer required in S-101 and proposals to retire some symbol definitions — so the transition is being managed carefully, symbol-by-symbol, rather than a clean swap.

Summary.

There won't be an "S-52 for S-101" as a separate cross-referenced document the way mariners are used to. The display rules will be part of S-101 itself (its portrayal catalogue), with the additional change that the rules can be updated from within the S-101 ENC itself.

Details of the above topics and S-100 more generally are at the IHO web site.