USCG Exam PracticeLatitude, longitude, and geographic coordinates
A mariner measures the distance between two points on a Mercator chart using dividers. Against which scale must the measurement be taken?
- A. The longitude scale at the top or bottom of the chart
- B. Any convenient portion of the latitude scale, since the scale is uniform on a Mercator chart
- ✓ The latitude scale at the latitude of the line being measuredCorrect
- D. The latitude scale at the equator, where one degree equals one nautical mile
Why C is correct
On a Mercator projection, meridian length varies with latitude, so distance must be measured on the latitude scale at the working latitude. One minute of latitude equals one nautical mile. The longitude scale must never be used for distance measurement.