On July 18, 2017, a Leopard 46 catamaran struck a reef and became grounded while approaching Huahine in the Society Islands, French Polynesia, at night.
We were very sorry to learn of this unfortunate incident.
The Navionics chart of Huahine is a correct reproduction of the French Hydrographic Office official chart, and by direct experience, because we have sailed that island, as well as comparison with satellite imagery, it is quite accurate.
Despite our accuracy, charts have errors whether it is a result of survey errors or source errors. This applies to ALL charts, whether government or private, official or otherwise. The International Hydrographic Organization stated that less than 10% of the seas are charted as well as the Moon, and even that 10% contains errors. This is why the common rules of navigation require that skippers, in addition to official charts, use multiple sources of information, including sailing directions, cruising guides, radar, sonar, local diligence and good eyesight; one should never get close to coral reefs at full speed and at night, 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 be spotted from a distance, and that possible uncharted coral heads be avoided.
One telling example is the recent grounding of the U.S. minesweeper USS Guardian on a reef reported 8 miles away from its true position by the official government chart. The US Navy discharged the captain and three senior officers because they “did not adhere to standard US Navy navigation procedures”; in other words, despite the error in the chart, the accident would have been avoided by applying common navigation rules.
It is also to be noted that by international standard for nautical charts, blue tint means shallow, not deep water, and the darker the blue, the shallower the water. This is because for safety and clarity, routes are drawn on white background.
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. A review of this topic can be found here https://www.navionics.com/blog/post/proper-use-of-electronic-charts/.