Just because you’re using digital charts (either raster navigational charts or electronic navigational charts) — either in an electronic charting system (ECS) common aboard tugs and other limited-tonnage vessels or a full-fledged IMO type-approved electronic chart display and information system (ECDIS) typically found on ships — instead of paper charts, the accuracy issues highlighted by new Zone of Confidence (ZOC) diagrams are not necessarily solved.

It is important to understand that inaccuracies and uncertainties can occur equally regardless of whether you are using paper or digital charts. The information used for each approved chart generally comes from the same sources. In most cases it is charted to the same World Geodetic System 1984 (WGS-84) reference coordinate system used by GPS (see your individual charts for confirmation of this important variable) and carries all of the same inherent limitations and deficiencies.

There are several articles that you should read as soon as possible in order to get a better grasp of chart accuracy and the new ZOC diagrams. Even mariners who think they already know all they need to know should read these articles.

First, “NOAA introduces Zones of Confidence; mind your ZOC,” published on panbo.com, the marine electronics hub.

That story led me to “How accurate are nautical charts?” at NOAA Coast Survey.

Another excellent source is “Safe Navigation with Uncertain Hydrographic Data” at Hydro International.

While we’re on this subject, you should expand your knowledge and perspective on all things GPS related on land, sea, and in the air by reading “Pinpoint: How GPS Is Changing Technology, Culture And Our Minds,” by Greg Milner. The book is eye opening on many levels.