【Geography Comprehensive】Maps and GIS: "Tools" for Understanding the World Accurately
Hello everyone! Welcome to your geography studies. Let's learn about "Maps and GIS" together.
You might be thinking, "Isn't it enough just to look at maps on my smartphone?" However, understanding how maps work doesn't just reveal the true nature of the world; it also helps you protect yourself from disasters and discover business opportunities.
It might feel difficult at first, but it’s easy once you grasp the key points. Let’s go through it slowly using everyday examples!
1. Globes vs. World Maps
The Earth is round, but maps are flat. Every story about map-making starts from this act of "forcing something round into a flat shape."
Globes (The most accurate representation)
Since a globe is just a smaller version of the Earth's actual shape, it is almost entirely accurate regarding "area," "distance," "direction," and "shape."
Analogy: Like a real apple itself.
- Pros: Everything is accurate.
- Cons: Hard to carry, you can’t see the whole world at once, and it’s hard to see fine details.
World Maps (Flattened projections)
To spread a sphere out onto a flat surface, you have to cut or stretch it somewhere.
Analogy: Like peeling an apple and forcing the skin flat onto a table. Some parts will inevitably tear or wrinkle, right?
- Pros: Easy to carry and allows you to view the entire world at once.
- Key point: On a flat map, it is absolutely impossible to correctly represent "area, distance, direction, and shape" all at the same time. You must choose the right map for your specific purpose.
💡 Trivia: The orange peel experiment
Try drawing continents on an orange peel with a marker, then try to flatten it out. It will definitely tear somewhere. How we deal with these "gaps" is what differentiates map projection methods.
2. Various Ways to Draw Maps (Map Projections)
Let's master the three projection methods that appear most frequently on the Common Test!
① Mercator Projection (Accurate angles)
Also known as a conformal projection. It is characterized by meridians and parallels intersecting at right angles.
- Features: Because angles are accurate, it has traditionally been used for nautical charts (navigation).
- Weakness: The closer you get to the high latitudes (near the North or South Poles), the more the area is exaggerated and stretched.
- Caution!: Greenland looks roughly the same size as Australia, but in reality, Australia is about 3.5 times larger!
② Azimuthal Equidistant Projection (Accurate distance and direction from the center)
Distance and direction from the center point are drawn accurately.
- Features: A straight line drawn from the center represents the shortest route (great-circle route). It is useful for checking flight paths.
- Weakness: Distances and directions from points other than the center are inaccurate. Also, the shapes become heavily distorted the further you go from the center.
③ Mollweide Projection (Accurate area)
Also known as an equal-area projection.
- Features: Because areas are represented accurately, it is suitable for distribution maps showing things like population or climate.
- Appearance: The entire map has an elliptical shape, similar to a rugby ball.
【Summary: How to choose】
・For sea travel: Mercator
・For the shortest flight route: Azimuthal Equidistant
・For statistical data: Mollweide
3. Indicating Location and Time Differences
Latitude and longitude are the "addresses" of the Earth.
Latitude and Longitude
- Latitude: The Equator is \( 0^\circ \), extending \( 90^\circ \) north and south. These are the horizontal lines.
- Longitude: The Prime Meridian, passing through the former Greenwich Observatory in London, is \( 0^\circ \), extending \( 180^\circ \) east and west. These are the vertical lines.
Calculating Time Differences
The Earth rotates once (\( 360^\circ \)) in 24 hours.
Calculation: \( 360^\circ \div 24 \text{ hours} = 15^\circ \)
In other words, there is a 1-hour time difference for every \( 15^\circ \) of longitude.
Point: Standard Time Meridians
These are the meridians that countries use as their reference. Japan uses \( 135^\circ \) East longitude, which passes through Akashi City in Hyogo Prefecture, as its standard.
Since the time difference from London (\( 0^\circ \)) is \( 135 \div 15 = 9 \), Japan is 9 hours ahead.
Common Mistake:
When crossing the "International Date Line" to the east (toward America), you go back one day. When crossing to the west (toward Asia), you advance one day. It can be confusing, so it’s fun to remember: "Going from west to east lets you return to yesterday!"
4. GIS (Geographic Information System) and Remote Sensing
Modern maps are primarily digital. This is one of the most important points in "Geography Comprehensive"!
GIS (Geographic Information System)
A system that links map data with various information (population, altitude, store locations, etc.) on a computer.
Analogy: Imagine stacking multiple transparent sheets.
- Layers: By stacking a "topography sheet," "road sheet," and "hazard map sheet," you can analyze where danger lies or where a new store should be opened.
- Usage examples: Selecting evacuation sites, planning store locations, and smartphone map apps.
Remote Sensing
A technology that uses satellites or aircraft to observe the Earth from a distance.
It is useful for grasping the conditions of places humans cannot easily reach (deserts, deep in the Amazon, disaster areas, etc.).
Point:
Collect data with remote sensing, analyze with GIS. This combination is the ultimate tool in modern geography.
5. Reading Topographic Maps (Basics of Map Reading)
You also need the ability to read paper maps (topographic maps). Let's start by learning these basics.
Contour Lines
Lines connecting points of the same elevation.
- Closely spaced: Steep slope (steep hill).
- Widely spaced: Gentle slope (flat land).
How to remember map symbols (Common examples)
・卍: Temple
・⛩️: Shinto Shrine (shape of a torii gate)
・文: Elementary/Junior High School
・(○ with a check-mark inside): City Hall / Town/Village Office
⚠️ Common Mistake: City Hall vs. Government Office
◎ (Double circle) is a City Hall, while a single circle with a check-mark-like symbol inside represents a "Town/Village Office" or "Government Office." They look very similar, so be careful!
Key Takeaways
1. The Earth is round!: When flattening it, there will always be distortion (you must sacrifice area, distance, direction, or shape).
2. Projection by purpose: Mercator for navigation, Azimuthal Equidistant for flight routes, Mollweide for distributions.
3. The magic number for time zones: 1 hour per \( 15^\circ \) of longitude.
4. GIS is about layering: A technology that analyzes different information by stacking it in layers.
5. Contour line spacing: Narrow means steep, wide means gentle.
Great work! "Maps and GIS" is a field with the same kind of fun as solving a puzzle. Start by opening a map app on your phone and thinking, "Which projection am I looking at right now?" or "What could I discover if I analyzed this location using GIS?" I’m rooting for you!