Proper use of electronic charts

Boaters are a passionate bunch, whether they are sailors, cruisers or anglers. Along with the ultimate enjoyment of the seas and lakes, comes a responsibility to the safety of passengers and fellow boaters. Murphy proved long ago that accidents can and will inevitably happen, and while unfortunate, often provide an opportunity for the boating community to take an introspective look at the tools we rely on while navigating. No single tool replaces the necessary use of sound judgement and proper seamanship. Most boaters employ the good practice of consulting multiple chart sources and regularly updating cartography, while each has its benefits and limitations. Proper understanding of an electronic chart is just as important as vessel maintenance and operation. In fact, reliance on electronic charts should never be done blindly, since all charts have errors (official hydrographic office, government, private, or other).

We in the cartography industry strive for perfection, employing multiple sources, modern survey methods and, most recently, crowd-sourced user feedback. But we know that, due to constant natural and manmade changes in the environment, the limitations of our technology and human error, no one will ever produce a perfect chart. Oftentimes, charts of reefs and remote islands are created from very old and inaccurate surveys.  With over a billion features in our cartography database, even an accuracy rate of 99.999% would still leave room for some 10,000 potential inaccuracies. No chart, regardless of the source, can avoid this simple mathematical rule. In fact, the International Hydrographic Organization stated that less than 10% of the seas are charted as well as Mars and the Moon, and even that 10% contains lots of errors. The Norwegian Hydrographic Office, in an official statement, estimates that as many as 35,000 rocks in Norway are uncharted.

The GPS available on boats is equivalent to the GPS on cars and light aircraft: meant to be used for visual orientation while driving, possibly with the aid of other instruments like sonar and radar, and cross checking every possible source of information. The nautical chart, whether paper or electronic, is not designed and built for instrumental navigation, but for orientating visual navigation. The warnings that go with all charts are not there to protect the chart makers, but rather to protect the chart users from making mistakes in over-reliance on any one tool of navigation.

The principles of prudent navigation imply that skippers understand that electronic charts are an aid to navigation to be used in addition to official charts and multiple sources of information, including sailing directions, cruising guides, radar, sonar and most importantly, common sense and good eyesight. Even with the best chart in the world, one should never get close to coral reefs or any obstruction at high speed or in low visibility, but rather when the sun is highest, at very slow speed, and with a person on watch on the bow of the boat. This is the only way to ensure that breaking waves can be spotted from a distance, and that possible uncharted coral heads and rocks be avoided. Skippers must also be aware that by international convention, in nautical charts the blue tint means shallow, not deep water, and the darker the blue, the shallower the water. This is because, in conventional navigation, one plots routes with a pencil on white paper, avoiding the tinted areas.

Not all cartography producers are bound to these presentation standards and can learn from firsthand accounts how mariners are interpreting electronic charts. Even though the recognized standard is dark blue for shallow waters, electronic charts allow the freedom to explore new ways to highlight hazards for the benefit of the boating community who may not have been taught the ways of old or may no longer be navigating with paper and pencil. As an example, reef areas can be highlighted to attract attention regardless of knowledge or experience level. This is a deviation from IHM standard coloring that Navionics first introduced in the Bahamas, a geography well known for its shallow water, coral reefs, and shifting sands and will now release worldwide.

Huahine French HO raster chartNavionics Huahine chartHuahine Navionics chart

Find here a collection of helpful information and interesting articles regarding the dangers of improper use of electronic charts. We share these with you in order to help us all improve safety at sea, since few boaters have not yet had some grounding experience.

 2017 July
This story reports on the grounding of a Leopard 46 catamaran on a reef while approaching Huahine at night. As a result, the family of 6 onboard was rescued by a French Navy helicopter and their boat damaged beyond repair. It provides insight on safer navigation practices, including the careful use of multiple cartography resources, satellite imagery and an alert lookout.
2016 January
This is a report by an experienced captain whose 37’6” yacht hit a submerged reef that had been marked as an island and sank.
Note that we, Navionics, have double checked all the official charts for the area from SHOM (France Hydrographic Office), UKHO and Indian HO, in addition to our competitors. Our chart is a correct reproduction of the official SHOM chart, but others represent the area as a drying area, or a rock that covers and uncovers, or a rock surrounded by an obstruction line, others yet show nothing at all. A review of the best available satellite imagery shows that without doubt there is a large reef; whether the best way to portray it is land, drying land, or a cluster of rocks, could be debatable. From the Volvo Ocean Race incident (see below), as an example, we have learned that it is best to “exaggerate” hazards, lest they go unnoticed by the navigator, a practice that is routinely done by Hydrographic Offices, and again we have faithfully reproduced what was done by SHOM.
2015 September
This article is about a charter boat that hit a submerged reef and sank.
2015 March
This article is about the use of electronic charts for safe navigation and how they compare to paper and raster charts. This is the Navionics perspective. 
See also the March 2015 news article by Theo Stocker linked below.
2014 November
This article links to the full official report surrounding the grounding of the Vestas during the Volvo Ocean Race.
You may learn more on this topic by reading the news article “Vector charts ‘not to blame’ for shipwreckby Theo Stocker from Yachting Monthly magazine. In it, several experts, who agree on the importance of using multiple sources of navigational information, are cited, including this one: ‘The rules of prudent navigation say that one should never rely on a single source of information,’ says Giuseppe Carnevali, president of Navionics. ‘Unfortunately some have the wrong impression that an electronic chart, just because it is electronic, must be so perfect that one can rely on it blindly.’
2014 April
Find here statements and advice on the use of nautical charts, including a brief comparison between paper versus electronic, and the importance of backups. Since all charts have errors, Navionics has developed ways for boaters to make and benefit from edits and corrections using modern technology, such as Community Edits and daily updates.
Read our Press Release regarding Navionics partnership with Norwegian Hydrographic Office to document thousands of uncharted rocks with the help of boaters reporting them on Navionics Boating app.
2013 April 
Steering Clear of Trouble Photos and Text by Ralph Naranjo
The article overviews various cartography resources along with importance of each, citing several boating disasters as examples.
2013 February
Find here a lengthy forum discussion, which includes several entries by Giuseppe Carnevali, regarding the grounding of Next Life. Though initially blamed on Navionics chart errors, several forum contributors point out how it may have been prevented using redundant chart references and caution in this tricky area. Specific to this incident, Community Edits reported by users show the rocks since one year prior and would have been available along with chart updates published in the Exumas, which are available on a daily basis to Navionics customers.
2013 January
Find here an article about the grounding of a US Navy vessel and resulting lengthy comments section.
USS Guardian Grounding Investigation Results Released
This news story from U.S. Pacific Fleet Public Affairs provides a brief summary of the findings of the U.S. Navy investigation.
Poor leadership, planning led to USS Guardian hitting reef near Philippines, report finds
A more detailed news article cites strong criticism of the leadership and crew’s failure to reconcile differences between navigational maps, as well as other errors, that are included in the U.S. Navy official report.
USS Guardian (MCM-5) Wikipedia
USS Guardian Wikipedia page describes the grounding and includes details of the chart errors, which inaccurately display the reef nearly 8 nautical miles away, as well as human errors in not comparing charts from other sources, which contributed to the incident.