Maps, OS map skills and GIS

Getting Started with Map Skills

Welcome! Maps are essentially the "language" of Geography. They allow us to take the massive, complex world and shrink it down onto a piece of paper or a screen so we can understand it. Whether you are navigating a hike or planning where to build a new city, map skills are vital. In your Edexcel GCSE (9-1) Geography B course, you’ll need to master Ordnance Survey (OS) maps, understand different types of imagery, and learn how GIS is changing the way we look at the world.

Don’t worry if these skills feel a bit like "Maths-in-Geography" at first—with a few simple tricks, you’ll be reading maps like a pro!

1. Understanding OS Map Scales

The scale of a map tells you how much the land has been "shrunk" to fit on the paper. For your exam, you need to know two specific types of OS maps:

• 1:25,000 scale: This is often called the "Explorer" map. It is very detailed. On this map, \(1 \text{ unit}\) on the map equals \(25,000 \text{ units}\) in real life. A simple way to remember this is: \(4 \text{ cm}\) on the map \( = 1 \text{ km}\) on the ground.
• 1:50,000 scale: This is the "Landranger" map. It covers a larger area but with less detail. On this map, \(2 \text{ cm}\) on the map \( = 1 \text{ km}\) on the ground.

Quick Tip: If the second number is smaller (25,000), the map is more detailed because it hasn't been shrunk as much!

2. Finding Your Way: Coordinates

To find specific locations, we use grid references. Always remember the golden rule: "Along the corridor and up the stairs." This means you read the numbers along the bottom (Eastings) first, and then the numbers up the side (Northings).

4-Figure Grid References

These point you to a whole \(1 \text{ km} \times 1 \text{ km}\) square.
Example: If a church is in a square where the bottom-left corner is Easting 42 and Northing 18, the reference is 4218.

6-Figure Grid References

These are more precise and point to a specific spot within that square. You imagine the square is divided into 10 smaller sections.
Example: 425182. The '5' tells us the spot is halfway across the square, and the '2' tells us it is just a little bit up from the bottom.

3. Showing the Shape of the Land (Relief)

Maps are flat, but the world is bumpy! Geographers use several methods to show relief (the height and shape of the land):

• Spot Heights: A simple dot with a number next to it showing the exact height above sea level in metres, e.g., \( \bullet 154 \).
• Contour Lines: These are orange or brown lines that join points of equal height.
  • If contour lines are close together, the slope is steep.
  • If contour lines are far apart, the land is relatively flat.
• Gradient: This refers to how steep a slope is. You can calculate this by looking at how much the height changes over a certain distance.

Cross-sections and Transects

A cross-section is like taking a "slice" through the landscape. It shows you the side-profile of a hill or valley. A transect is a line across a map where you might record changes in things like vegetation or land use as you move from one area to another.

4. Different Types of Maps and Images

The exam might ask you to interpret more than just a standard OS map. You should be familiar with:

• Isoline Maps: These use lines to link areas of equal value. Contours are a type of isoline, but you might also see them used for temperature (isotherms) or travel time.
• BGS Geology Maps: Created by the British Geological Survey, these show the types of rock (igneous, sedimentary, or metamorphic) beneath the surface. This is very useful when studying Topic 4 (The UK's Physical Landscape).
• Sketch Maps: Simple, hand-drawn versions of a map or photo that highlight only the most important features, like a river or a main road.

Photographic Evidence

Geographers use different "viewpoints" to see the world:

• Vertical Aerial Photos: Taken from directly above (like looking down from a plane). Great for seeing land-use patterns.
• Oblique Photos: Taken from an angle. These are helpful because they show the sides of buildings and the height of hills more clearly than a vertical photo.
• Ground Photos: Taken from a person's eye level on the street. Good for seeing details like shop signs or house types.
• Satellite Imagery: Taken from space. Used to see massive scales, like tracking a tropical cyclone or seeing the extent of a megacity.

5. GIS (Geographic Information Systems)

GIS is essentially a "digital map with layers." Instead of just one paper map, a computer allows us to stack different types of data on top of each other.

How it works: Imagine a map of a city.
Layer 1: The road network.
Layer 2: Areas at risk of flooding.
Layer 3: Locations of elderly residents.
By layering these, a geographer can quickly see which people might need the most help during a flood. GIS geo-spatial data is used by governments, businesses, and researchers to make complex decisions quickly.

Quick Review: Common Pitfalls to Avoid

1. Forgetting the units: In Geography, height is almost always in metres and distance is in kilometres or miles. Always check the map key!

2. Mixing up Eastings and Northings: If you go "up the stairs" before "along the corridor," your grid reference will be completely wrong. Always read the horizontal (bottom) numbers first.

3. Scale confusion: On a \(1:50,000\) map, remember that \(1 \text{ cm} = 50,000 \text{ cm}\) in real life. To make that useful, we convert it: \(50,000 \text{ cm} = 500 \text{ metres}\). Therefore, \(2 \text{ cm} = 1 \text{ km}\).

Key Takeaway: Map skills are about precision. Take your time with your ruler and your finger when tracing grid lines, and always use the key (legend) to identify symbols—never guess!