Lecture Notes: Maps, Projections, and Thematic Maps

Latitude and Longitude

Mats are flat pictures of our round Earth. They use special lines to help us find places!

• Latitude lines are like imaginary belts that go all the way around the Earth, from east to west. We call them "parallels" because they never touch each other.

  • The most important latitude line is the Equator, which is right in the middle of the Earth at 0^\text{°}. It's like the Earth's belly button!

  • Latitude tells you how far north or south a place is from the Equator. If you go north from the Equator, the latitude numbers go up (like 10^\text{°}N, 20^\text{°}N). If you go south, the numbers also go up (like 10^\text{°}S, 20^\text{°}S).

  • For example, the 45th parallel is a special line 45^\text{°} north or south of the Equator.

• Longitude lines are like imaginary stripes that go up and down, from the North Pole to the South Pole. We call them "meridians".

  • The most important longitude line is the Prime Meridian, which is at 0^\text{°}. It runs through a place called Greenwich in England. This line helps us figure out time zones.

  • Longitude tells you how far east or west a place is from the Prime Meridian. If you go east, the longitude numbers go up (like 10^\text{°}E, 20^\text{°}E). If you go west, the numbers also go up (like 10^\text{°}W, 20^\text{°}W).

• How to read directions: Sometimes maps use letters like 'E' for East or 'W' for West. If it says x^\text{°}E, you move to the right on the map. If it says x^\text{°}W, you move to the left.

• Finding places: You can use latitude and longitude together like a secret code to find any spot on Earth! For example, if you see 36^\text{°}N, 140^\text{°}E, you know it means go north to the 36^\text{°}N line and east to the 140^\text{°}E line. That spot is Tokyo on a world map.

Map Distortion and Projections

Imagine peeling an orange and trying to make its round skin lie perfectly flat without tearing or stretching it. It's impossible! Our Earth is round like an orange, and when we try to flatten it onto a map, something has to change.

• Distortion is always there: Every flat map of our round Earth will make some things look a bit wrong. It might make countries look bigger or smaller than they really are, or change their shapes, or make distances seem longer or shorter.

• Different maps, different tricks: Maps use different "tricks," called projections, to try and get things as right as possible, but they always have to choose what looks best and what gets a little distorted.

Map Projections (overview and examples)

Here are some popular map "tricks" and what they are good and bad at:

• Mercator projection:

  • Good for: Sailors! It helps them steer their ships in the right direction because all the angles are correct.

  • Bad for: Showing the true size of places. Countries far from the Equator (like Greenland or Russia) look HUGE, much bigger than they actually are. Countries near the Equator look smaller than they really are.

  • Remember: Greenland looks ginormous on Mercator maps, but it's not actually that big.

• Robinson projection:

  • Good for: A good middle ground! This map tries to make everything look pretty balanced, so nothing is too distorted. It has a nice, rounded shape (like a "robin" egg).

  • Bad for: It's not perfect. There's still a little bit of stretching, especially at the edges, but it's much better than Mercator for overall fairness.

• Interrupted projection (also called interrupted equal-area):

  • Good for: Showing the true size of landmasses! It cuts up the oceans so that all the countries are shown in their correct size, making it easy to compare how big they really are.

  • Bad for: Sailors! With all the oceans chopped up, it's impossible to use it for navigation or planning routes across the water.

• Peters projection (Gall–Peters projection):

  • Good for: Showing the true size of landmasses, especially places like Africa and South America. It tries to be fair about how big continents really are, so places like Africa look much bigger than on a Mercator map.

  • Bad for: The shapes of countries. While the size is right, the shapes can look stretched or squished, making them look a bit funny.

• A projection used for true direction and size in airline navigation:

  • Good for: Pilots! This map helps airplanes find the shortest and most direct path to fly from one place to another, even if it looks like a curved line on a flat map.

• Summary of map tricks:

  • Mercator: Great for sailing, bad for showing true size far from the Equator.

  • Robinson: A good, balanced map that looks pretty fair.

  • Interrupted: Shows true land size but chops up the oceans.

  • Peters: Shows true land size but makes country shapes look stretched.

  • Airline map: Helps planes fly the fastest routes.

Map Types: Reference vs Thematic

Maps also come in two big families:

• Reference maps: These are like guidebooks. They help you find places and see what the land looks like.

• Thematic maps: These are like storybooks. They tell you a special story about one particular thing, like where lots of people live or where it snows a lot.

Reference Maps

These maps help you find where things are:

• Political map: Shows the borders between countries, states, and cities. It's like seeing all the property lines on the Earth.

• Physical map: Shows natural things like big mountains, long rivers, and deep valleys. It's about what the Earth's surface actually looks like.

• Topographic map: Shows even more detail about the land's height. It uses special curvy lines (called contour lines) to show hills and valleys. Great for hikers to know if they're going up or down a big hill!

Thematic Maps

These maps focus on one special topic or story:

• Dot map:

  • How it works: Little dots are placed on the map. Each dot stands for a certain amount of something. For example, one dot might mean 100 people.

  • Example: An election map might use dots to show where people voted for different parties. Or a map showing where different racial groups live, with different colored dots for each group.

• Isoline map:

  • How it works: This map draws lines that connect all the places with the same value. It's like connecting all the dots that got the same amount of rain or snow.

  • Example: Weather maps often use isolines to show how much snow fell in different areas or where the temperature is the same.

• Flow line map:

  • How it works: Uses arrows of different thicknesses to show movement. Thicker arrows mean more movement, and the arrows show the direction.

  • Example: A map showing people moving from one country to another, or how oil and coffee are shipped around the world. It can even show how a disease spreads.

• Choropleth map:

  • How it works: Different areas (like states or countries) are colored or shaded. The darker the color, the more of something there is.

  • Example: A map showing how many people live in each state (darker states have more people) or how many kids die young in different parts of the world.

• Graduated symbol map (or graduated symbolization):

  • How it works: Uses symbols (like circles or little hearts) that change size. Bigger symbols mean there's more of something, and smaller symbols mean less.

  • Example: A map of a country showing divorces. A big broken heart symbol might mean many divorces, and a tiny one means very few.

Practice and Application

Learning about maps is like learning a new game! We practice finding coordinates and interpreting different types of maps to understand the world better.

Connections to Foundational Principles and Real-World Relevance

• Why it matters: Because Earth is round, flat maps will always have some stretching or squishing. Knowing this helps us understand maps better.

• Choosing the right map: We pick different maps for different jobs. A pilot needs a different map than someone who wants to see where the mountains are.

• Being smart about maps: Understanding map types helps us look at information carefully. We can tell if a map is showing us true size, how many people, or movement, and also what might be distorted.

• Everyday uses: Maps help us hike, plan trips, understand election results, or even see where a disease might be spreading.

Key Takeaways (easy to remember!)

• Latitude lines go sideways (east-west); Longitude lines go up and down (north-south).

• The Equator is the middle latitude line at 0^\text{°}. The Prime Meridian is the middle longitude line at 0^\text{°}.

• When you go East on a map, the longitude numbers usually go up (to the right).

• All flat maps stretch or squish the Earth a little. Different maps do it in different ways (like Mercator, Robinson, Peters).

• Reference maps help you find places. Thematic maps tell you a story about one specific thing (like dot maps, flow maps).

Notation and Formulas

• Equator's special number: 0^\text{°} latitude

• Prime Meridian's special number: 0^\text{°} longitude

• Example location code: 36^\text{°}N, 140^\text{°}E means Tokyo

• Latitude lines: They run horizontally around the world.

• Longitude lines: They run vertically from pole to pole.

• Directions: Going towards the east means the longitude number gets bigger.