By Ben Ellison
From Hand-Drawn to Databased, Part II
|NOAA is going vector and free while private vendors hustle to stay ahead.|
Last month I wrote reverently about the history of nautical charts and not so reverently about certain bits of monkey business we’re experiencing as they transition from paper to electronic form. Too many formats, too much incompatibility, royalty wars—times of change can be messy. But, in this month’s continuation of the discussion, I bring you mostly good news.
Let’s start with NOAA’s misunderstood but radical Electronic Navigation Chart (ENC) project. ENCs are the beginning of a true vector chart system, a concept that needs explaining. I’ll use the San Francisco ENC above for visual reference. It covers some of the same area as shown last month with an 1853 paper chart (a bit of which is overlaid). Only instead of being hand-drawn by a skilled and artistic cartographer, probably wearing a starched collar and a green eyeshade, the ENC was drawn by a computer.
Never mind for now how much more elegant the 1853 chart looks and how it actually appears more detailed, even though the creators lacked even motorboats for their work, let alone GPS, depthsounders, or graphic workstations. Compared to the paper system, ENC vector technology is an entirely different animal, and one just beginning its evolution. An ENC is not even a drawing. If you translated the file into our alphabet, which is possible, you’d find thousands of tightly coded lines similar to this: “L4-102, 37.809439, 122.427391, Y2.5,...” It might reference a library file containing the symbol for that light buoy at upper left on the ENC (and in data box below), along with its lat/lon and unique details. It’s a record in a database, and the software that “draws” it onto the screen can do so in very flexible ways. If you want the lights to disappear or show in an alternate symbol set, no problem, just check some boxes with your mouse. By contrast, a raster file is just a stubborn list of pixel locations and colors, like a digital photograph.
But you may already understand this, as the vector charts produced by C-Map, Garmin, Transas, etc. share the same characteristics. Several things set ENCs apart. For one, they are official government cartography. In fact, since they’re based on the International Maritime Organization’s S57 standard, they are official international vector charts. More significant is that ENCs will eventually become NOAA’s base technology, tentatively the world’s. Even though the first set is being made mostly by tracing the existing raster charts, in due time the data will remain real data, not pixels, from start to finish. For instance, some of the current ENCs use original Corps of Engineers channel dredging records and Coast Guard buoy locations instead of the less accurate representations that were drawn into the limited- scale paper system.
That’s what I mean by true vector technology, and it makes so much sense compared to the current situation. Contemplate the silliness of surveyors sending GPS numbers describing a coastline into the home office where the data becomes curves on a raster file to which the vector vendors arduously apply special tracing software in order to turn it back into numbers! Realize that when the Coast Guard moves a buoy in an all-vector system, the tiny change record can be e-mailed into NOAA and out to vessels—zing, zing—where the relevant chart is instantly updated.
There’s more. You might hear around the chart shops that ENC coverage is meant mainly for ships and will not include all the current paper detail, but NOAA electronic chart products manager Mike Brown says it isn’t so. While he can’t cite a completion date, he says that ENCs will in due time duplicate the entire U.S. paper portfolio and then replace it. And NOAA is giving them all away. Dozens of “cells”—the charts are organized in multiscaled regions instead of familiar paper sizes, another sign of the future—are available for downloading right now at chartmaker.noaa.gov. Several free viewing programs are available on the Web, and charting programs Fugawi and MaxSea can plot on ENCs; others like The Cap’n will follow soon.
This article originally appeared in the April 2004 issue of Power & Motoryacht magazine.