Satellite Imagery in AP Human Geography

From a picture of rooftops to a new city park

A city planning department pulls up satellite images and sees that a few neighborhoods are almost entirely pavement and rooftops (impervious surfaces, meaning water can't soak through), with very few trees. Those blocks also tend to run hotter. The planners decide to put new parks there first.

That chain of events is what Topic 1.3, The Power of Geographic Data, in Unit 1 asks you to explain. The image is the data, the park is the choice, and the cooler, greener neighborhood is the spatial consequence. The course wants you to see that this works at every scale and for three kinds of decision makers:

• Personal: someone checks imagery before buying a house to see whether it sits near a floodplain or a highway.
• Business or organization: a conservation group maps deforestation, or a retailer looks at where new housing is being built before choosing a store site.
• Government: a public health agency combines satellite imagery showing standing water with health records showing disease clusters, then decides where to drain land or add clinics.

What an image shows about a city, and what it leaves out

Satellite imagery returns in Topic 6.9, Urban Data, in Unit 6, where the bigger question is what causes change inside cities and what that change leads to. Imagery is great at the physical side of urban change. You can watch farmland turn into subdivisions on the urban fringe, measure how much green space a neighborhood lost, or see new construction cluster along a highway.

An image can't tell you who lives in those buildings or how residents feel about the change. For the size and makeup of an urban population (age, income, race, household size), you need census data and surveys, which are quantitative. For how people experience change, like longtime residents' reactions to gentrification, you need qualitative sources such as interviews and field studies.

A strong answer about urban change often pairs sources. Imagery shows new apartment towers in an old industrial district, census tracts show rising median income there, and interviews show displaced residents' frustration. Each source covers a different piece of the cause-and-effect story.

Satellite imagery vs. remote sensing vs. GIS

These three get blurred together. Remote sensing is the broad method of collecting information about Earth from a distance, using satellites, aircraft, or drones. Satellite imagery is one product of that method. Aerial photos from a plane also count as remote sensing, but they aren't satellite imagery.

GIS (geographic information systems) is the software that layers imagery with other data, like population, income, or road networks, so you can analyze patterns. A quick way to keep them straight is to treat remote sensing as how the data is gathered, satellite imagery as what gets gathered, and GIS as where it gets analyzed.

If a multiple-choice stem stresses the technique of collecting data from far away, remote sensing is the better fit. If it describes images being used to spot a pattern, satellite imagery fits.

Reading scenario stems that start with a satellite map

When a question opens with a satellite map of clinics and villages, the imagery is usually setup, and the answer is often the geographic concept behind the pattern. Other questions ask you to identify satellite imagery as a data source, interpret a pattern it shows, or use it to evaluate a geographic decision, so follow the wording of the question.

For example, a stem might say health records show vaccination rates dropping steadily as distance from the nearest clinic grows, and that satellite imagery was used to map where the clinics and surrounding villages are. That pattern is distance decay, the idea that interaction and access weaken the farther you get from a place. The imagery located the clinics and communities, and the health records supplied the rates. The concept doing the explaining is distance decay.

On the free-response section, Question 2 (One-stimulus question) and Question 3 (Two-stimuli question) can use images or maps as stimuli, so a satellite image or a map built from one is a fair possibility. A top answer names what the image actually shows, connects it to a decision someone could make, and explains the consequence of that decision at a stated scale. Analyzing across scales is one of the course skills, so be ready to say how the same imagery informs a local choice (one neighborhood's park) and a national or global one (tracking deforestation across a country).