Data Sources and Types

Two different ways to classify geographical evidence

Geographical information helps us understand places, processes and people's experiences. Measuring a river tells us about its size and flow; photographs show its surroundings; residents' accounts can reveal their experiences of flooding. These sources answer different questions, so using them together can give a fuller understanding than using just one.

Quantitative data are numerical information obtained by counting, measuring or scoring. Examples include river width in metres, pedestrian numbers and the percentage of questionnaire respondents choosing an answer. Numbers make comparisons and calculations possible.

Qualitative data describe qualities, observations, experiences or opinions through words or images. Examples include a field sketch of a valley, a photograph of coastal erosion and an interview response explaining why someone feels unsafe in a street. These can show detail and meaning that a count alone would miss.

A second classification concerns where the information comes from. Primary data are collected first-hand by the investigator or fieldwork group. Secondary data were collected or published by someone else. The two classifications are independent: primary does not mean numerical, and secondary does not mean descriptive.

The classification depends on how you obtain and use the information. Your own fieldwork photograph is primary evidence; an existing photograph taken by someone else is secondary evidence for your investigation.

Obtaining information from different sources

The best source depends on what you need to find out. Primary fieldwork can supply detailed information about a particular site, while secondary sources can provide wider coverage or evidence from earlier dates.

• Maps show locations, distributions and relationships between features. A map can locate river measurement sites or show land uses around flood defences. Read its key, scale and date before interpreting it: the symbols explain what is mapped, while the scale determines how much detail can be shown.
• Fieldwork data include measurements, counts, surveys, photographs and sketches. A pedestrian count records how busy a street is during a particular observation period; an open interview can explain why people visit it. Record locations, dates, times and measurement units so that results can be understood and compared.
• Written and digital sources include council planning documents, newspaper reports, websites and residents' accounts. They can explain decisions and experiences, but consider who produced them, when and for what purpose. An account of someone's experience is evidence of their perspective, not necessarily the experience of everyone in the area.
• Visual and graphical sources include photographs, field sketches, diagrams and graphs. Photographs show visible conditions; graphs organise numerical information to make patterns easier to see. Check annotations, graph axes, units and keys before drawing conclusions.
• Numerical and statistical information includes census figures, weather records and published flood data. These can reveal patterns across larger areas or longer periods than a short field visit. Check the geographical area, time period and meaning of each measure before comparing figures.

Satellite imagery provides images of Earth's surface captured from satellites. It is normally secondary evidence for a school investigation. Examine the image date, area covered and any key or labels before interpreting visible patterns. Images can help identify the arrangement of features across an area, but they do not directly explain people's opinions or the reasons behind a change. Combine them with maps, records or field observations to investigate those questions.

How GIS connects data to places

Spatial data are information linked to locations. A Geographical Information System (GIS) stores, displays and analyses these data digitally. It can bring together different layers of information on the same map, allowing you to investigate where features occur together.

Spatial features can be represented as points, such as survey sites; lines, such as roads or rivers; and polygons, which are enclosed areas such as land-use zones. Information attached to these features can include both numerical values and descriptions.

Imagine an investigation of a fictional town's streets. One GIS layer contains roads, another contains land-use areas and a third contains survey-site points. Each point has an attached pedestrian count and an observation about the street. Selecting a point lets you examine its recorded information; displaying the layers together lets you compare the count with its surroundings.

For example, if higher counts appear at sites in shopping areas, you have identified a possible spatial relationship. You could then use interview responses to investigate why those streets attract visitors. The map alone does not prove that shops caused the higher counts.

The same method transfers to real GIS data: check the layer keys, dates, locations and attached information, then compare distributions. GIS makes data easier to edit and analyse, but it cannot make inaccurate or incomplete source data trustworthy. This fictional diagram demonstrates the method, not the geography of a real town.

Turning evidence into clear communication

Presentation should match the information and the point you want to communicate. Tables organise results; bar charts compare categories; line graphs show change in continuous data, such as temperature over time. Maps communicate location. Annotated photographs and sketches draw attention to relevant visible features, while short quotations communicate people's explanations.

Consider these results from a fictional street survey. Each count covers a ten-minute period.

A bar chart would make the differences in counts easy to compare. A map would show where the sites lie. Annotated photographs or the written observations would communicate the character of each street. Keep the count period in the title or caption so readers know what the figures mean.

To interpret the evidence, explain what it shows: Site C had the most pedestrians during the observation period. To analyse it, connect pieces of evidence: the higher counts occurred at sites where more shops were observed. A possible explanation is that shops attract visitors, although the bus stop and other factors may also influence movement.

Evaluating what the evidence can support

Evaluation means judging how useful and dependable the evidence is for the question being investigated. Consider accuracy, consistency, coverage and possible bias rather than assuming that a source is strong simply because it contains numbers.

The fictional survey provides evidence about three sites during short observation periods. It does not establish how busy the streets are all day. Repeating counts at comparable times on several days would help test whether the differences persist. Counts taken at different times may reflect changing activity rather than differences between streets.

Qualitative evidence also needs evaluation. A photograph may exclude nearby features or lack scale; an interview records one person's view. Published information may be out of date or cover a different area from your fieldwork.

Combining sources allows you to check whether their findings agree and to explain what each contributes. A count can show a difference, a map can locate it, and an interview can suggest a reason. Your conclusion should reflect both the evidence and its limits.

Classify the evidence

Use two independent classifications:

Closed questionnaire responses can be counted; open responses give descriptive explanations.

Choose and read sources

• Maps: locations and distributions; check key, scale and date.
• Fieldwork: site-specific measurements, counts and observations; record location, time and units.
• GIS: combines location-linked layers; points, lines and polygons represent spatial features.
• Satellite imagery: surface patterns; check date, coverage and labels.
• Written/digital sources: explanations and perspectives; check author, date and purpose.
• Visual/graphical sources: visible features or numerical patterns; read annotations, axes and keys.
• Statistics: comparisons across places or time; check units, areas and periods.

Use and judge information

Communicate: choose tables, graphs, maps or annotated images to suit the data.

Interpret: explain what the evidence shows.

Analyse: connect patterns with other evidence and possible explanations.

Evaluate: judge accuracy, reliability, coverage, currency and bias. State how a limitation affects the conclusion.

Combine numerical and descriptive evidence. A spatial relationship can suggest an explanation, but does not by itself prove causation.