Boating navigation is more about attention to detail than anything else. Sure, it requires a certain amount of understanding and a good deal of education on the hows and whats, but when it comes down to it, even the most knowledgeable chart reader can overlook the most minor of details. For those of us not tuned to the chart reading channel, one look at a nautical chart could inspire that sinking feeling of confusion mixed in with discourage. That is why, One Stop Motors wants to help with the basics to reading a nautical chart. After this, you’ll be a regular conquistador, comfortably gliding the glistening waters of your local waterway.
The first thing one should do when looking over a nautical chart is to not panic. It is daunting, the way the map is covered in grid lines and more numbers than a multiplication table. The purpose of all these numbers is to show depth. If the number is on land, then that is most likely the height of the land mass. For water, it is the depth from the surface to the bottom. This is the most important thing to know as the depth of the water might be too shallow for larger boats. If you have one, you won’t be powering through a small, shallow channel because if you’re boat hits the bottom of the waterway, you are not going to like what happens next (think Titanic). You will notice how waters closer to shore have smaller numbers and the further out the deeper it gets.
Most charts will have some sort of topographic scale for identifying depth or rather the drop offs in depth. When a number goes from 50 to 80 all the sudden, you’ll see a line somewhere between where the bottom tappers down. These lines are generally dotted or dashed and unlike the latitude or longitude lines that run strait, they will run in wavy stretches. This will be how you can identify sandbars and serious depth differentials. Again, if you’re bringing a big boat into the shore, you’ll need to know if you are about to hit a much shallower area and if that deepness is safe for your hull.
When it comes to detail, nautical charts work well in displaying any obstacles that may be in the way of your course. For example, if you’re travelling through a channel or a river and a bridge is up ahead, a nautical chart will have the bridge displayed with it’s height and length. Now you’ll know if it is feasible to cross under it or if you need to find a new course. Generally, nautical charts help in identifying where you are on your present course. If you see a small island just off the coast and match that with your chart, you’ll have a good idea of your own location.
Keeping your charts up to date will allow you to account for any sort of recent activity or additions. Using a chart, however, has become somewhat of a dead art since the evolution of navigational technology. Now, with a good navigational system, the leg work in planning a course is calculated for you. Plug and play as they say. Still, having a chart on-board is essential in the event of a navigation malfunction. The last thing you want is to be stranded off coast with a dead navi system and no nautical chart. However unlikely this is, it can happen. Hence the lesson.
Tyler Baker; OSM Writer
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