Unfortunately GPS/Chartplotters prior to this year require the operator to do the plotting. That is, we must plot a course on the chart display around obstacles, in channels etc. that will safely take us to our destination with each straight line beginning and ending at a "waypoint." The plotters could not "see" these hazards intrinsically, even though they appear on the chart, in order to do it automatically.
However, Garmin's 2007 line of plotters, when using the optional and expensive Bluechart G2 Vision card you can use what Garmin calls Auto Guidance and the plotter will indeed chart a safe course when given just the start and end points. No more straight lines across solid ground. how well this technology works remains to be seen but it sure is something to contemplate.
