Wednesday, May 8, 2024

Landmark Labels on ENC

We are one of the first in line to lament the poor coverage of terrestrial charting in electronic navigational charts (ENC) compared to the paper chart coverage we are used to.  And for good reason: we do most piloting relative to landmarks and much of the land mass on ENC is conspicuously blank—which can appear even more moonscape vacant depending how we have the display set up, as shown below.

Unlike viewing raster navigational charts (electronic copies of the paper charts), ENC let the user control many aspects of the display. Above we see an example of choosing to show "Important text only," which is a (misleading) official ENC display option.

If we compare that to what we see on the equivalent paper chart, we see what we are missing in that view.

It is not just the names that can be hidden, but NOAA ENC have very few elevation contours which can often help with piloting. 

Another reason we care about charted place names is a matter of basic safety and prudent seamanship. We teach that it is good policy to always keep in mind a verbal description of where you are, and maybe even note it in the log book that way, ie "Just passing west of Willow Island." Knowing this at all times we are prepared to describe our position over the radio in an emergency—which is much faster than finding, if you can, a read out of the Lat and Lon and reading that with its potential error.  Furthermore it makes the cruise more enduring if you learn these names as you go by.  The say-it-out-loud method is is also how we teach students to learn the stars in cel nav.

Thus these charted place names are valuable to navigation. But things are not so bad as they might appear.  They can be bad, as shown above, but they do not have to be. Below we turn on the text labels to see what we really do have in ENC.

The charted place names are actually all there on the ENC, they are just not as prominent as they are in the paper charts, which have the freedom to use large font sizes for some, and indeed print on a curve.

ENC have strict international rules of font size and orientation, although in some cases they do let labels (and associated symbols) move on the chart so that critical ones remain in view as you change the screen.  A folded paper chart on the chart table may be just hiding a note that a dashed line is marking a restricted Navy firing zone. On the equivalent ENC if you panned that notice off the screen it would suddenly reappear in a new position in view. 

In other words, the use of labels on an ENC is just one more aspect of the new chart reading skills we need to develop for ENC. We have to look at the charts in a new way. One thing that helps with this is the rule that  ENC chart symbols and labels stay the same size regardless of the display scale (zoom level). Thus crucial matters may become more apparent as we zoom into the region of interest.

The Future of ENC

As for other deficits of the terrestrial coverage of existing NOAA ENC, we can be confident that this will improve. First of all, a few nations do a better job with the elevation contours already, and the US certainly has extensive GIS data for all aspects of US mapping. 

To show that big agencies like NOAA should be able to solve this problem fairly soon, we can show how to do this ourselves already.  Beyond its outstanding ENC display presentation, the popular navigation and weather app qtVlm also offers the option to overlay on the chart GIS data as shape files  (.shp), a standard format for GIS data. 

In the sample below, I followed the instructions we have online  to add the roads to Lopez Island and water bodies and elevation contours to Blakely Island, and then (within qtVlm) limit the contours to the 100 ft intervals shown on the paper chart.

Once these are installed, we can get a tool tip presentation of the road names, heights of elevation contours, and related data for water bodies. In fact we learn there are more lakes on Blakely Island than the paper chart showed.

In other words, there is good reason to expect that the terrestrial coverage of future ENC will be even more valuable than that of the paper charts they are replacing. 

We are likely to see this take place first in the printed versions of the ENC called
NOAA Custom Chart (NCC). These are intended to be the (non-official) paper backups of the official ENC viewed on a computer screen or chart plotter.  NCC are user-created online from the NOAA NCC app that produces a PDF chart of the desired region, scale, and paper size, based on the ENC content for that region.  Then it is up to the user to get the chart printed at the chosen paper size.

It is during this NCC production that NOAA could offer the GIS overlay options such as elevation contours, roads, building, water bodies, etc to be added to the PDF they are creating... essentially just as qtVlm offers users the option as shown above. Thus we could end up with a new-generation of paper charts that are indeed superior to what we are now accustomed to.

Seeing this new data in the actual ENC themselves is likely further down the line. Even though a few other nations already have better contours, roads, and buildings, NOAA is likely pretty tied up with their massive process of rescheming all the ENC, which is a major ongoing improvement to the watery parts of the ENC. Not to mention that all nations are in the long process of preparing for the next generation of ENC, where the present IHO S-57 standard will be replaced by the new S-100 standard, which inherently includes a lot of new GIS content. These proposed changes are discussed in our text Introduction to Electronic Chart Navigation.

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