There may be as much as three fathoms difference between contour lines in deep water. If you are using a larger scale chart, contour lines will only be included for greater changes in depths. Not every chart is measured in feet and fathoms. Always check the scale on your chart to be sure, though. So a place on a chart that depicts a contour line will show a change in depth by one fathom, or six feet. The lines are usually represented in fathoms. Contour lines depict the underwater landscape. These sometimes will shade from lighter blue to darker blue. If you’re looking at a nautical chart, you’ll see lines that create irregular, blobby shapes in the water. Especially if there are things you want to see and/or avoid.

Why it matters: If you’re planning a trip, it’s always good to know the actual distance. When the entire chart covers a massive area, one nautical mile can be imperceptible. Measuring distance is easier on small craft charts. Check the scale on your chart to determine just how much area is being covered. A harbor chart covers areas close to shore. Harbor charts are typically the most detailed. A large scale chart could be just a general chart or a coastal chart. Large scale charts offer less detail but cover a larger area.Harbor charts may have a scale around 1:20,000. Small scale charts offer greater detail but cover a smaller area.A chart from Canada will not use inches and the scale will be different. Make sure you check the units on your chart, however. So one nautical mile will be around 2.5 inches. That means 1 inch is about 0.4 nautical miles. If the scale is 1:30,000 it means that 1 inch on your chart equals 30,000 inches in real life. Obviously there are times when either will be appropriate. You can choose between a small scale chart and a large scale chart. But there are also international charts in other countries. The National Oceanic and Atmospheric Administration makes many nautical charts. Let’s take a look at how and why you should read nautical charts. If you need to know where to find red buoys and green buoys, the nautical chart has your back. Things like land contours, water depths and more are included. Nautical charts specifically depict water areas of importance. They show you where you are as well as what else should be there. Even if you’re on the Great Lakes by the cabin, using a chart is always a good idea.Ī nautical chart conveys what you can see and what you can’t. It’s outdated and, if you know where you’re going, why bother? But there’s a lot more to a nautical chart than showing you just a map of water. For many boaters, it’s like owning a road map. No paper nautical charts and no electronic nautical charts available either. We offer a variety of sizes and pricing.There’s more than one boat owner out there who doesn’t have access to any nautical charts. Click on one of the options below to get started. We now have five options for chart artwork that are perfect for home or office. This chart is available for purchase online. Printed “on-demand,” it contains all of the latest NOAA updates as of the time of printing.

The chart you are viewing is a NOAA chart by OceanGrafix. This chart contains all of the latest NOAA updates at the time of printing and is available for purchase online or from one of our retailers. This edition number now overrides the NOAA edition number. *Under the guidance of NOAA's Office of Coast Survey, this chart has amassed enough critical and non-critical corrections such that OceanGrafix has issued a new edition number.

Green bay contour map