Atlas maps and direction

Geographical skills start with reading maps. On an atlas map, place is given by latitude (lines running east–west, measuring degrees north/south of the Equator) and longitude (lines running north–south, measuring degrees east/west of the Prime Meridian).

Direction is given using a compass:

• The 8-point compass: N, NE, E, SE, S, SW, W, NW.
• The 16-point compass adds the in-between directions (e.g. NNE, ENE, SSW).

Key idea: geographers use maps at different scales — from a world atlas down to a detailed local map. The Ordnance Survey (OS) maps of Great Britain are the ones you use most for grid references.

OS maps and scale

An OS map is drawn to a scale — the ratio between distance on the map and real distance on the ground. You mainly meet two scales:

• 1:25,000 — very detailed; 4 cm on the map = 1 km on the ground (each grid square is 4 cm across).
• 1:50,000 — covers more area; 2 cm on the map = 1 km on the ground (each grid square is 2 cm across).

To measure a straight-line distance, use a ruler; for a curved distance (a winding road or river), lay a piece of string or paper along it, mark the length, then measure it against the scale bar.

Why 4 cm = 1 km at 1:25,000? 1 cm on the map stands for 25,000 cm on the ground. 25,000 cm = 250 m, so 4 cm = 1,000 m = 1 km. At 1:50,000, 1 cm = 500 m, so 2 cm = 1 km.

Grid references: four-figure vs six-figure

OS maps are covered by a grid of numbered blue lines. The vertical lines are eastings (numbers increase to the east →) and the horizontal lines are northings (numbers increase to the north ↑). Always read easting first, then northing — "along the corridor, then up the stairs".

Reading a four-figure reference

Pinpointing with six figures

A four-figure reference only tells you the square. To be more precise, imagine the 1 km square divided into a 10 × 10 grid of tenths.

• Read the easting of the bottom-left corner, then add how many tenths to the right your point is.
• Read the northing, then add how many tenths up your point is.

So for a point in square 4321 that is 5 tenths across and 7 tenths up, the six-figure reference is 435 217 — the extra digit is inserted after each pair.

Common slip: keep easting and northing in order. The first three digits are the easting (43 + 5 = 435) and the last three are the northing (21 + 7 = 217). Never swap them.

Which is a six-figure reference?

Using scale to measure distance

Contours, relief and symbols

OS maps show relief (the shape and height of the land) using:

• Contour lines — thin orange lines joining places of equal height. Lines close together = a steep slope; lines far apart = a gentle slope.
• Spot heights and triangulation pillars — an exact height printed at a point.

Maps also use symbols to pack in information — a blue P for parking, a small cross for a church, a blue triangle for a youth hostel and so on (check the map key). You can use symbols, contours and grid references together to describe a route or draw a cross-section or sketch map.

Describing relief: use contour patterns and spot heights — e.g. "the land rises steeply from 50 m to 200 m in the north-east, then flattens into a plateau." Always support a description with figures from the map.

Choosing the right graph

Different data suit different graphs. AQA expects you to choose and interpret a wide range:

• Line graph — continuous change over time (e.g. temperature through the year, population growth).
• Bar chart / histogram — comparing separate categories or grouped data.
• Pie chart / divided (compound) bar — proportions of a whole (percentages that add to 100%).
• Scatter graph — the relationship (correlation) between two variables.
• Climate graph — bars for rainfall and a line for temperature on the same axes.
• Also: pictograms, triangular graphs, radial graphs, flow-line/desire-line maps, isolines, choropleth and dot maps, and proportional symbols.

Scatter graphs and correlation

A scatter graph plots one variable against another to show whether they are linked. The pattern of points shows the correlation:

Watch out: correlation does not prove one thing causes the other. A scatter graph shows a relationship, but there could be another factor behind it.

Picking the best graph

Reading a climate graph

A climate graph combines two data sets: bars for average monthly rainfall (read off the right-hand axis) and a line for average monthly temperature (read off the left-hand axis).

Mean, median, mode and range

These measures of central tendency (plus range) summarise a set of data:

• Mean — add up all the values and divide by how many there are.
• Median — the middle value when the data are put in order.
• Mode — the value that occurs most often.
• Range — the highest value minus the lowest value (a measure of spread).

Calculate the mean

Find the median

Match the statistic to its meaning

Tap a statistic on the left, then tap its correct definition on the right.

Percentages, percentage change and ratios

Geographers often compare data using:

• Percentages — a part out of 100. E.g. if 30 of 120 residents cycle to work, that is 30 ÷ 120 × 100 = 25%.
• Percentage change — (change ÷ original) × 100. If a village grows from 40 to 50 people, the change is 10, so 10 ÷ 40 × 100 = 25% increase.
• Ratios — comparing two amounts, e.g. 20 cars to 5 buses simplifies to a ratio of 4 : 1.

When reading a table of data, look for the biggest and smallest values, describe the overall trend, and pick out any anomaly — a value that does not fit the pattern.

Checked: 30 ÷ 120 × 100 = 25%. From 40 to 50 is a rise of 10; 10 ÷ 40 = 0.25 = 25% increase. 20 : 5 divides by 5 to give 4 : 1.

Quantitative vs qualitative data

Geographers collect two kinds of data:

• Quantitative data — numbers and measurements you can count or record precisely (e.g. a pedestrian count, rainfall in mm, traffic totals). It can be put straight into graphs and calculations.
• Qualitative data — opinions, descriptions and feelings that are not numbers (e.g. a resident's view on traffic, a description of how a place feels, a photo caption).

Tip: if you can put it in a table of numbers, it's quantitative. If it's someone's words, opinion or a description, it's qualitative. Good fieldwork often uses both.

Quantitative or qualitative?

Tap the correct data type for each piece of data.

Line graph or pie chart?

Tap a data set, then tap the box for the best way to show it.

Your turn — describing data

Geographic Information Systems (GIS)

A GIS is a computer system that stores, displays and analyses spatial (map-based) data as separate layers that can be switched on and combined on one map.

GIS is used to choose a shop site, plan flood defences, map disease spread, manage satnav and much more — anywhere different spatial data need to be combined and analysed.

Your turn — what is GIS?

The key ideas to know

You've covered the whole AQA GCSE Geographical Skills unit. Press Finish to see your score.