This cheat sheet helps students remember that longitude lines run from the North Pole to the South Pole. Longitude is important because it tells how far east or west a place is from the Prime Meridian. Students use longitude with latitude to find exact locations on maps and globes.
The memory aid makes it easier to avoid mixing up longitude and latitude.
Key Facts
- Longitude lines run from the North Pole to the South Pole.
- Longitude lines are also called meridians.
- The Prime Meridian is 0 degrees longitude and passes through Greenwich, England.
- Longitude measures distance east or west of the Prime Meridian.
- Longitude is written in degrees east or west, such as 75 degrees W or 30 degrees E.
- Lines of longitude meet at the North Pole and the South Pole.
- Latitude and longitude work together as a coordinate pair to locate places on Earth.
Vocabulary
- Longitude
- Longitude is a measure of how far east or west a place is from the Prime Meridian.
- Meridian
- A meridian is a line of longitude that runs from pole to pole.
- Prime Meridian
- The Prime Meridian is the 0 degrees longitude line used as the starting point for measuring east and west.
- North Pole
- The North Pole is the northern end of Earth's axis where longitude lines meet.
- South Pole
- The South Pole is the southern end of Earth's axis where longitude lines meet.
- Coordinate Pair
- A coordinate pair uses latitude and longitude together to describe an exact location on Earth.
Common Mistakes to Avoid
- Confusing longitude with latitude is wrong because longitude lines run pole to pole, while latitude lines run side to side around Earth.
- Saying longitude measures north or south is wrong because longitude measures east or west from the Prime Meridian.
- Forgetting E or W after a longitude number is wrong because 40 degrees E and 40 degrees W are in different directions from the Prime Meridian.
- Drawing longitude lines as flat horizontal lines is wrong because meridians curve on a globe and meet at both poles.
- Using longitude alone to find an exact place is wrong because a location needs both latitude and longitude.
Practice Questions
- 1 A city is located at 20 degrees E longitude. Is it east or west of the Prime Meridian?
- 2 Which longitude line is the starting line for measuring east and west: 0 degrees, 45 degrees N, or the Equator?
- 3 A map label says 90 degrees W. What does the W tell you about the location?
- 4 Explain why the phrase 'longitude lines are long pole-to-pole lines' is a helpful memory aid.
Understanding Longitude lines run pole to pole Memory Aid
Earth is close to a sphere, so mapmakers need an agreed system for describing positions on a curved surface. Longitude divides a full trip around Earth into 360 equal angle measurements. Each degree represents a small turn from the reference line, not a fixed number of miles.
Near the Equator, one degree of longitude is about 69 miles. Closer to either pole, the distance between neighboring meridians becomes smaller because the lines draw together.
At the poles, there is no space between them. This explains why longitude is useful for direction but does not give the same ground distance everywhere.
The choice of a starting meridian is a human agreement. Greenwich became the international reference in 1884, when many countries chose it for navigation and mapmaking. Before that decision, different countries sometimes used different starting lines.
A shared reference made charts easier to compare and helped ships communicate their locations. On the opposite side of Earth, around 180 degrees longitude, lies the International Date Line.
It does not follow one perfectly straight path because it bends around islands and national borders. Crossing it can change the calendar date by one day.
Longitude has a close connection to time. Earth turns 360 degrees in about 24 hours. This means it turns about 15 degrees each hour.
Places farther east see noon earlier than places farther west. Time zones are based partly on this pattern, though their borders are changed to match countries, states, and cities.
A student in New York may be starting school while a student in London is already well into the afternoon. On a globe, following meridians from west to east helps show why this happens.
When reading coordinates, pay close attention to the letter after the number. East and west describe opposite sides of the reference line. A missing or incorrect letter can place a location on the other side of Earth.
Read latitude first when coordinates are written in the common order, then longitude. On a paper map, meridians may look vertical, curved, or unevenly spaced. That is caused by map projection, which is the method used to flatten Earth onto paper.
A globe shows their true pattern more clearly. Practice by finding a city, tracing its meridian toward both poles, then comparing its time zone with cities to the east and west.