Charting continued from page 49
ECDIS VERSUS ECS
route-checking function that’s similar to my suggested routine, highlighting areas of possible concern and making it easy to zoom in to investigate further. This can be done on electronic raster charts, at least for the U.S. The software also has the ability to “unquilt” the raster charts such that a user can see all the other information printed on the original chart.
Regardless of the level of sophistication available to me, I would always perform the final step of zooming in to the most detailed data level available and scrolling along the entire route to look for adjacent hazards. The software does not provide this lateral vision.
At sea, we use the autopilot much of the time, but we never connect it to the chartplotter. I extract a bearing to the next waypoint from the chartplotter and plug this into the autopilot. This way, the crew also has to stay alert and we immediately become aware of currents and other factors setting us off the track and can decide what to do about it, as opposed to having the autopilot correct for these factors. We maintain a written position log at least once an hour so that if the electronic charts crash we have a recent fix from which to begin a dead reckoning plot on the paper chart. Included on this log are the range and bearing to the waypoint and the cross-track error, which provide the necessary information to determine tidal and other influences.
If it becomes necessary to switch to paper charts, I have the skills to use parallel rules and other conventional plotting devices. We rely heavily on visual navigation in narrow channels and when close to any hazards. We have hand-bearing compasses and know how to fix positions with crossed bearings, transits, and so on. Unlike us, many big ships no longer carry paper charts. For years it has been legal for them to rely on vector-type electronic charts, but they must be official electronic nautical charts (ENCs) issued by a national hydrographic office and displayed on a type-approved electronic chart display and information system (ECDIS). The latter, in particular, has to comply with rigorous standards, one of which defines essential data that must be displayed at any zoom level, including shallow water soundings and hazards. Ships must carry a fully functional and independent backup system (which can be another ECDIS or traditional paper charts). This level of technology removes many of the problems with electronic charts that I have identified but is prohibitively expensive for recreational boaters and requires a lot of real estate in the navigation station.
An alternative, less rigorous standard to ECDIS has been developed by the Radio Technical Commission for Maritime Services (RTCM). This defines operational and performance requirements for electronic charting systems (ECS) other than ECDIS. It defines four categories of equipment—A, B, C,