Which scale is used to measure longitude on a nautical chart?

Which scale is used to measure longitude on a nautical chart?

• A. Latitude scale
• B. Longitude scale
• C. Mercator scale
• D. Distance scale

Answer: (B)

Longitude measures east-west position, so on a nautical chart the scale for reading longitude is laid out along the horizontal direction, usually along the top or bottom edge. Mariners read degrees, minutes, and seconds of longitude there to determine how far east or west they are from the Prime Meridian. Latitude, in contrast, is read from the vertical scale on the sides of the chart, measuring north-south position from the equator. The Mercator projection is a common chart type, but it doesn’t create a special “Mercator scale” for measuring longitude; you still use the longitude scale in degrees. A distance scale shows actual ground distance (nautical miles) for converting map length to real distance, not for reading angular coordinates.

Longitude measures east-west position, so on a nautical chart the scale for reading longitude is laid out along the horizontal direction, usually along the top or bottom edge. Mariners read degrees, minutes, and seconds of longitude there to determine how far east or west they are from the Prime Meridian. Latitude, in contrast, is read from the vertical scale on the sides of the chart, measuring north-south position from the equator. The Mercator projection is a common chart type, but it doesn’t create a special “Mercator scale” for measuring longitude; you still use the longitude scale in degrees. A distance scale shows actual ground distance (nautical miles) for converting map length to real distance, not for reading angular coordinates.