Topic 1.2 Notes – Geographic Data

What Geographic Data Is

Geographic data is any information tied to a place. A map shows it, but the data comes first.

• Spatial information tells you where something is.
  • Examples: coordinates, street address, place name, census tract, parcel boundary
• Attribute information tells you what that place is like.
  • Examples: population, income, language, land use, elevation, traffic, vegetation

Time matters too. A population count from 2010 and one from 2020 describe the same place at different moments, so geographers can measure change.

Geographic data can be quantitative or qualitative.

• Quantitative = numbers, like population density or rainfall
• Qualitative = descriptions, like residents explaining neighborhood identity

A common trap is treating a map as a collection method. Usually, a map is a display of data after it has been collected. In this topic, the key question is where did the data come from?

Main Ways Geographers Collect Data

Geographers first separate data by source.

Primary data

Primary data is collected directly for a specific investigation.

• The researcher decides when, where, and how to collect it.
• Examples:
  • pedestrian counts
  • water-quality testing
  • surveys and interviews
  • field photos
  • GPS points

Strengths and limits:

Secondary data

Secondary data was collected earlier by someone else and reused.

• Examples:
  • census data
  • land records
  • media reports
  • policy documents
  • published surveys
  • satellite imagery

Secondary data is great for large areas and long time periods, but the categories or dates may not fit your question.

Field collection

Field collection means gathering information directly at a location.

• Methods include counts, measurements, surveys, interviews, field notes, sketches, photos, and coordinate recording.
• The U.S. decennial census is a standard example of organized field collection.
• A census tries to count everyone. A sample survey studies a selected subset and uses it to represent the larger population.

Written, oral, and visual sources

Some spatial data comes from records and interpretation, not direct measurement.

• Media reports can show where an event happened and how it affected people.
• Travel narratives help with historical landscapes and perceptions of place.
• Policy documents show laws, zoning, and planned land use.
• Personal interviews reveal experience, identity, and perception.
• Landscape analysis reads visible evidence in buildings, roads, fields, fences, or signs.
• Photographic interpretation looks inside an image for clues like pattern, shape, tone, texture, and association.

Geospatial Technologies

The exam expects you to separate four technologies clearly.

GIS

GIS stands for Geographic Information System. It stores, layers, analyzes, and displays spatial data.

Its signature move is overlaying layers to find relationships.

• Possible layers: roads, flood zones, land use, hospitals, population

GIS overlay map of zoning and flood hazard layers

Satellite navigation systems

GPS is the best-known example. It uses satellite signals to calculate location.

• Gives coordinates, routes, and movement
• It tells you where you are
• It does not create images

Remote sensing

Remote sensing collects information about Earth from far away using satellites, aircraft, or drones.

• Used for land cover, deforestation, urban growth, crops, hazards
• Standard example: Landsat images over time
• Important terms:
  • spatial resolution = how much detail each image cell shows
  • temporal resolution = how often the same place is imaged
  • ground truthing = checking image interpretations with field evidence

The Las Vegas time series below is the kind of remote sensing image set you may be asked to interpret. Focus on the satellite panels that show the city spreading outward over time.

Landsat time series of Las Vegas urban growth

Online mapping and visualization

These are web-based interactive maps. They let users search, zoom, layer, and explore data. They often combine GIS, GPS, and remote sensing, and may include user-added information like road closures or geotagged uploads.

How to Tell the Methods Apart on the Exam

Match the clue to the method.

• Coordinates from orbiting satellites = satellite navigation
• Imagery from satellites, aircraft, or drones = remote sensing
• Layered analysis or overlays = GIS
• Interactive web map = online mapping
• Counts, surveys, measurements, interviews at a site = field collection
• News stories, laws, plans, diaries, agency records = documentary sources
• Buildings, roads, signs, fields used as evidence = landscape analysis
• Pattern, shape, tone, texture inside an image = photographic interpretation

One project can use several methods. The exam usually wants the specific function being described.

Limits, Verification, and Why Methods Are Combined

No dataset is perfect, so geographers care about:

• accuracy = closeness to reality
• precision = exactness
• resolution = level of detail
• currency = how recent it is
• completeness = what is missing
• consistency = same definitions and procedures
• representativeness = whether the sample reflects the larger group
• bias = systematic distortion

Common problems include census undercounts, weak survey samples, cloud cover in remote sensing, outdated online data, and interviews shaped by wording or interviewer effects.

Triangulation means using multiple methods or sources to strengthen a conclusion. Ground truthing is more specific. It means checking remote sensing or mapped interpretations with field evidence. That’s why the best method depends on the question. High-tech tools are useful, but they do not automatically give better evidence.