Map Projections and Coordinates

Grade 4 · Social Studies · Study Guide

Learn how geographers use map projections and coordinate systems to represent and locate places on Earth.

Earth is a sphere, but a map is flat. Cartographers (mapmakers) use map projections to transfer the curved surface of the Earth onto a flat piece of paper. Every projection has some distortion — it can distort shape, size, distance, or direction. No flat map can be perfectly accurate.

One of the most common projections is the Mercator projection, which shows direction well and is useful for navigation. However, it makes areas near the poles look much larger than they really are. The Robinson projection is designed to balance distortions and give a more realistic view of the whole world.

To find exact locations on Earth, geographers use a grid system of imaginary lines called latitude and longitude. Lines of latitude run east and west (horizontally) and measure how far north or south a place is from the equator. The equator is at 0 degrees latitude. Lines of longitude run north and south (vertically) and measure how far east or west a place is from the prime meridian, which runs through Greenwich, England, at 0 degrees.

Together, latitude and longitude form a coordinate system. Every location on Earth has a unique set of coordinates, written as degrees. For example, Washington, D.C. is located at approximately 39 degrees North latitude and 77 degrees West longitude. This system allows us to pinpoint any place on the planet.

Key terms

Map Projection: A method for showing Earth's curved surface on a flat map
Latitude: Imaginary horizontal lines that measure distance north or south of the equator
Longitude: Imaginary vertical lines that measure distance east or west of the prime meridian
Equator: The imaginary line at 0 degrees latitude that divides Earth into the Northern and Southern Hemispheres
Prime Meridian: The imaginary line at 0 degrees longitude that runs through Greenwich, England
Coordinates: A pair of latitude and longitude values that identify an exact location on Earth

Flashcards

Cartographer: A person who makes maps
Map Projection: A way to represent Earth's curved surface on a flat map; always involves some distortion
Latitude: Imaginary horizontal lines measuring degrees north or south of the equator
Longitude: Imaginary vertical lines measuring degrees east or west of the prime meridian
Equator: The 0-degree latitude line dividing Earth into the Northern and Southern Hemispheres
Prime Meridian: The 0-degree longitude line running through Greenwich, England
Mercator Projection: A common map projection useful for navigation but that distorts the size of areas near the poles
Coordinates: A latitude and longitude pair used to find an exact spot on Earth

Questions

What are lines of latitude used to measure?
1. Distance east or west of the prime meridian
2. Distance north or south of the equator
3. The height of mountains
4. The distance between cities
Show answer
Answer: Distance north or south of the equator
Latitude lines run horizontally (east-west) and are used to measure how far north or south a location is from the equator.
The equator is the imaginary line at 0 degrees latitude.
Show answer
Answer: True
The equator is the imaginary circle at 0 degrees latitude that divides Earth into the Northern Hemisphere (above) and Southern Hemisphere (below).
Why do cartographers use map projections?
1. To make maps look more colorful
2. To show Earth's curved surface on a flat map
3. To measure ocean depths
4. To track weather patterns
Show answer
Answer: To show Earth's curved surface on a flat map
Because Earth is a sphere but maps are flat, cartographers use projections to transfer the globe's surface onto paper, though all projections distort something.
Lines of longitude measure how far east or west a place is from the ____ meridian.
Show answer
Answer: prime
The prime meridian, located at 0 degrees longitude, is the starting line for measuring distances east or west around the globe.
A flat map can show the entire Earth with absolutely no distortion.
Show answer
Answer: False
It is mathematically impossible to flatten a sphere without stretching or compressing some part of it, so every flat map has some form of distortion.

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