USCG Exam PracticeLatitude, longitude, and geographic coordinates
When measuring distance on a Mercator chart using dividers, against which scale must the measurement always be taken?
- ✓ The latitude scale at the vessel's working latitudeCorrect
- B. The distance scale printed in the chart title block
- C. The latitude scale at the equator
- D. The longitude scale at the top or bottom of the chart
Why A is correct
One minute of latitude equals one nautical mile, but on a Mercator projection meridian length varies with latitude. Distance must therefore be measured on the latitude scale alongside the vessel's own working latitude, never on the longitude scale.