To measure distance on a Mercator chart between the parallels of LAT 34°30'N and LAT 31°30'N, which 30 mile scale should be used?

Correct Answer: Option B — 32°45'N to 33°15'N

Mercator chart projections suffer from scale distortion as latitude increases. To measure distance accurately, use the latitude scale centered on the mid-latitude of the distance being measured. The mid-latitude between 34°30'N and 31°30'N is 33°00'N; therefore, the scale from 32°45'N to 33°15'N provides the most accurate distance.