With years of cruising the Bahamas and the US, I have become accustomed to believing what the electronic charts say ( with a grain of salt). When we started cruising with Steve, he was quite insistent that we not only look at the electronic chart but plot our position routinely on the paper chart as well. Admirable, but it struck me as overkill. Not any more.
We have consistently had issues “out here”. We have found large differences between the Navionics electronic charts and the Jeppesen electronic charts. Both suffer from large unexplained gaps in coverage which we have laughingly referred to as falling off the earth. The British Admiralty paper charts aren’t much better – they date back to the late 1800’s or so and often don’t agree with any of our electronic charts.
We are currently in the northern Yasawa islands. When we do a radar overlay on the electronic charts, they frequently aren’t even close. When we do an actual plot on the BA charts, they aren’t any better – and none of our charts for this area have soundings.
So this is completely new to me – no soundings and inaccurate charts. Now I understand why Steve wants plots. So what does work when in rocky reefy areas (along with some nail biting, narrow, skinny areas) without soundings?
First, look out the window but hazy skies or bad light can make this really tough.
Second, look at the relationship between conspicuous objects on the electronic/paper charts and radar – while both the charts may be wrong, they do indicate the relationships between prominent features.
Third, watch the sounder, but this is where you have been versus what is yet to come. For the yet to come part, we have found the Furuno scanning sonar invaluable.
Forth, use the track function on your chart plotter, When it is time to leave (or come back) simply pull up your old track and follow it.
Fifth, have a good strong drink after a particularly nail biting transit once the big 240 pound Rocna anchor is hooked up and the scanning sonar has said that there is nothing hazardous within 100 meters.
Right now, it is blowing 20 to 30 knots, we are off a nice resort, the hook is down, Deb is at the pool and after a shower, we are headed ashore for dinner.