Full disclosure: I used to be a land surveyor, then a cartographer, then I went to work for NOAA on a hydrographic survey ship, all before the days of computers, GPS, ECDIS, etc.
Because of the unique path I took to becoming a mariner, I have always been aware of the limitations of the nautical chart. I vehemently agree that mariners are becoming more and more sucked into the “if it is digital it must be 100% accurate” syndrome associated with ECDIS, but I think that points more to complacency and poor situational awareness than anything else.
When NOAA conducts hydrographic surveys, they are extremely accurate. But only for that moment in time. Coastal waters are extremely dynamic. Natural shoaling occurs, earthquakes move sea beds, channels are dredged and new wrecks and obstructions are discovered. As you know, this information is promulgated as soon as possible in the US through Local Notice to Mariners and the NGA’s Notice to Mariners. It is up to the mariner to keep the charts corrected and updated.
That being said, a mariner must also take into account when a hydrographic survey was done, which you pointed out in your thread. Depths on any given NOAA chart may be based, in some areas, on hydrographic surveys conducted with leadlines prior to 1900, in other areas, on multibeam sonar surveys that attained full bottom coverage. Over 50 percent of the depth information found on NOAA charts is based on hydrographic surveys conducted before 1940.
NOAA has specified stringent accuracy standards for collection of data by its survey vessels. Currently, surveys are being conducted to DGPS accuracy. However, for surveys performed prior to the mid 1990’s (back in my day), the accuracy requirement was only 1.5mm at the scale of the survey. For example, on a 1:20,000-scale harbor approach survey, an accuracy of 1.5mm on the chart equates to 30 meters in real life.
This means to me that the prudent mariner should pass shoals or isolated dangers with utmost caution, no matter what navigation method is used.
Click here for a great web page on how accurate NOAA charts are, the limitations associated with survey data, and how blindly following a GPS trackline can get a mariner into trouble pretty quickly.