Spatial analysis and GIS

Learning objectives

• Distinguish vector and raster data and choose the right one for a given feature.
• Explain map scale and map projections, and why layers must share a coordinate system.
• Describe where spatial data comes from, including aerial imagery, LiDAR, and open data, and the privacy questions it raises.
• Describe buffer, overlay, and network analysis and the planning questions each answers.
• Explain land suitability analysis and its roots in McHarg's overlay method.
• Design a choropleth map that doesn't mislead, and explain the modifiable areal unit problem.
• Describe the gravity model and choose the right chart for a dataset.

Key concepts

What GIS does

A geographic information system (GIS) stores, analyzes, and displays data tied to locations. Its power comes from linking where something is to what it is: each mapped feature carries attributes in a table (a parcel's zoning, assessed value, and year built), so you can ask spatial questions like "Which vacant parcels zoned for housing are within half a mile of a transit station?"

8 more sections follow in the full lesson.

Key terms

• GIS: A system for storing, analyzing, and displaying location-based data.
• Vector data: Points, lines, and polygons representing discrete features.
• Raster data: A grid of cells representing continuous surfaces.
• Buffer: A zone of specified distance around a mapped feature.
• Overlay analysis: Combining map layers to identify where conditions coincide.
• Network analysis: Measuring distance or travel time along a real network.
• Land suitability analysis: Scoring and combining layers to rank locations for a use.
• Choropleth map: A map that shades areas according to a value.
• Normalization: Converting counts to rates or densities so areas of different sizes can be compared.
• Modifiable areal unit problem (MAUP): Results that change with the size or shape of the units being analyzed.
• Ecological fallacy: Inferring individual characteristics from group-level data.
• Gravity model: A model in which interaction rises with size and falls with distance.
• Map scale: The ratio of map distance to ground distance; a large-scale map shows a small area in detail.
• Map projection: A method of flattening the Earth onto a map, which always distorts area, shape, distance, or direction.
• State Plane Coordinate System: A set of U.S. coordinate zones designed to keep distortion low for local mapping.
• Spatial join: Linking features based on their location rather than a shared attribute.
• Remote sensing: Gathering information about the Earth's surface from aircraft or satellites.
• LiDAR: Laser-based measurement of elevation and surface features from aircraft.