More route planning; an efficient workaround for a poor ENC Electronic Nautical Chart display.
The transition to electronic map systems and ECDIS (Electronic Chart Display and Information System) does not reduce the need for route planning. On the contrary, there are several conditions in which navigators should plan their sailing route better and more accurately after such equipment has been installed.
Here are some examples of conditions that reduce the quality of ENC. You will also find these conditions in more detail in the attached presentation.
– ENC, S57 and S52 reproduce information poorer than that found on a paper map. Yes, many people – including me – have this opinion. Decide for yourself by comparing the paper chart and the ENC for a given area on the same scale. I’m sure you’ll find the way light sectors, underwater rock, text, and isolated danger are drawn in ENC to be unfavourable.
– Insufficient accuracy of depth data. High quality depth data is security graded. In Norway, this means that depth information with less than the 50 metre minimum distance between points is graded. All official ENC cells have a minimum distance greater than 50 metres. You will find similar regulations throughout the world.
– The distance between deep contours is too large. In an ENC one will find the same depth contour levels as on a paper map. This is usually 0, 2, 5, 10, 20, 30, etc. When the Safety Contour is set just more than a contour in the ENC, the ECDIS will choose the next deeper level. This creates major problems for alarms and viewing of what is a called safe navigation waters.
– The distance between spot depths is too large. An option to display safe navigation waters is to set Safety depth to safe water. If so, you will find safe water spot depth in gray colour, and more shallow spot depths i bold. If this shall work there must be a high density of spot depths. Unfortunately, such maps only exist in some areas.
This means that one cannot trust the grounding alarm will work, grounding alarm is one of the most important features of ECDIS. In the case of too many alarms, which may force ships to turn off the acoustic alarm, the ship may rely on their own visual studies of the map.
Route planning in ECDIS should definitely not just include draw courses in the electronic map or retrieval of a saved route file that someone else created. There must be more in-depth study of the electronic map (ENC), describing safe manoeuvring areas in narrow waters, displaying alternative navigation methods in critical areas, as well as creating secondary routes. In contrast, not knowing the waters along the route, alternative navigation marks for course changes, or safe navigation areas make necessary manoeuvres due to unforeseen events riskier.