Data Sources and Types

Geographers often use hybrid methods to bridge this gap. An Environmental Quality Survey (EQS) quantifies subjective judgements by asking observers to rate an area using a bipolar scale (e.g., -3 to +3) or a Likert scale (1 to 5).

Collecting Primary and Secondary Data

Every time a local council builds a new flood defence, they rely on multiple layers of historical and real-time evidence.

• Primary Data is collected first-hand by the researcher. This can be physical (measuring beach profiles) or human (conducting land-use mapping).
• Secondary Statistical Source data is pre-existing information collected by external bodies, such as the ONS Census, World Bank, or Environment Agency.
• Secondary Written Sources are pre-existing documents, such as newspaper articles and council planning documents. These are crucial for providing temporal context (showing how a place has changed over time) and capturing different stakeholder perspectives.

When designing primary fieldwork, geographers start with a Hypothesis, which is a clear, directional, and measurable statement to be tested. To ensure data is representative, they use sampling strategies. Random sampling gives every location an equal chance of selection, Systematic sampling takes measurements at regular intervals (like every $50\text{m}$ along a transect), and Stratified sampling ensures sub-groups are proportionally represented.

Safety is also critical during primary collection. Geographers must complete a risk assessment to identify hazards and manage risks. For example, if the hazard is "slippery rocks," the risk is "injury from falling," and the management strategy is "wear sturdy footwear and work in pairs."

Maps, Satellites, and GIS

Looking down at Earth from space reveals spatial patterns and hidden relationships that are entirely invisible from the ground.

Ordnance Survey (OS) Maps are traditionally used at scales of $1:25{,}000$ ($4\text{cm} = 1\text{km}$) and $1:50{,}000$ ($2\text{cm} = 1\text{km}$). They indicate relief using spot heights, triangulation pillars, and contour lines drawn at $5\text{m}$ or $10\text{m}$ intervals.

Remote Sensing involves obtaining information about the Earth from a distance without physical contact. Different satellite sensors capture different spatial data:

• Visible light: Shows features exactly as the human eye sees them, such as sediment plumes or city lights.
• Infrared: Detects thermal heat, which is vital for spotting rising magma in volcanoes or identifying urban heat islands.
• Radar: Unlike visible light, radar does not rely on clear skies; it penetrates clouds and works at night, making it ideal for rapid flood assessment.

Geographical Information Systems (GIS) are computer-based tools for capturing, storing, and analysing this spatial data. By Georeferencing data to exact latitude and longitude coordinates, GIS allows for advanced spatial analysis. Key functions include Layers (Strata) to overlay different thematic maps, Filtering to remove visual clutter, and Buffering to create a specific zone (e.g., a $500\text{m}$ radius) around a feature.

Worked Example: GIS Flood Risk Analysis

GIS is incredibly powerful for decision-making. To prioritise flood defences, an analyst would follow these steps:

1. Load the Base Layer (a Digital Elevation Model showing land height).
2. Overlay the Hydrology Layer (showing river networks and historical floods).
3. Overlay the Human Layer (showing infrastructure and population density).
4. Identify the exact intersections where vulnerable populations meet high flood risk.

Statistical Skills and Data Presentation

Finding the average of a dataset is useful, but simple averages can easily hide extreme weather events or massive economic inequalities.

Geographers use measures of central tendency, including the Mean, Median, and Mode. However, to understand the spread of data, the Interquartile Range (IQR) is preferred over the simple range. The IQR focuses strictly on the middle $50\%$ of ranked data, successfully ignoring Anomalies (data points that do not fit the general trend).

To communicate this data clearly, geographers use specific presentation methods. A Choropleth Map uses varying shades of colour to represent average values in different areas. An Isoline Map uses continuous lines to connect points of equal value, such as isobars for pressure or isotherms for temperature.

Worked Example: Calculating Percentage Change

Geographers frequently manipulate secondary data to compare growth or decline over time.

Formula:

$$\text{Percentage Change} = \frac{\text{New Value} - \text{Old Value}}{\text{Old Value}} \times 100$$

Question: A town's population grows from 200 to 250. Calculate the percentage change.

Step 1: Identify the known values.

• Old Value = $200$
• New Value = $250$

Step 2: Substitute the values into the formula.

• $\text{Percentage Change} = \frac{250 - 200}{200} \times 100$

Step 3: Calculate the numerator, divide, and multiply by 100.

• $\frac{50}{200} = 0.25$
• $0.25 \times 100 = 25\%$