Latitude and Longitude

Every sectional is covered by a grid of latitude and longitude lines. Lines of latitude run east and west. They tell you how far north you are. Lines of longitude run north and south. They tell you how far west you are.

This chart draws a line every thirty minutes. Sixty minutes make one degree. Small ticks mark each minute. Medium ticks mark five minutes. Long ticks mark ten. Here is the key fact. Along a line of longitude, each tick is one minute of latitude, and one minute of latitude is one nautical mile.

Ticks along a line of latitude mark minutes of longitude. They shrink as you go north. Here, each one is only about eight tenths of a mile. Do not measure distance with them. Now find Salinas Municipal. It sits at thirty-six degrees, thirty-nine point seven minutes north. Count nine point seven ticks up from the thirty-six thirty line. Its longitude is one hundred twenty-one degrees, thirty-six point four minutes west. Count six point four ticks west of the one twenty-one thirty line.

Now measure Salinas to Monterey. Lay the distance along a line of longitude. It is about twelve nautical miles.