How to Measure Nautical Chart Distances

A nautical map can be confusing when you're first learning to use one. However, follow these instructions, and you'll be able to measure distance on a nautical map with just a little practice.

Things You'll Need

• Nautical chart
• Divider

Instructions

1. Locate the starting position on the nautical chart. This may be the location where you are currently located or it may be a location that you wish to measure distance from.

2. Locate the finishing point on the nautical chart. This is the location you're measuring the distance to. You must know the exact locations of both the starting and finishing positions to get an accurate measurement of distance.

3. Take out your divider. This is the instrument that looks similar to the compass that you might have used in geometry class. Place the point of the divider on the starting position.

4. Open the divider so that you can put the other point on the finishing position.

5. Move the divider to the closest latitude scale. Don't open or close the divider, or you may get an inaccurate measurement. Keep it open exactly as it is when the 2 points rest on the starting and finishing locations.

6. Place one of the divider's points on a whole number on the latitude scale. Swivel the divider so that the other end falls on the latitude scale.

7. Subtract the first number from the second to determine how many degrees the 2 points are apart from each other. One degree is equal to a nautical mile. You now know how many nautical miles the 2 points are from each other.

Tips & Warnings

• By putting the first divider on zero degrees, you won't have to subtract the numbers. The number that the second point falls on is the distance.

• Always use the latitude scale rather than the longitude scale.