When you’re working with geographic data, maps can help reveal patterns and tell a story. Some common patterns are:
Clusters,
Islands,
Alignment, and
Division.
Here's how to identify them on a map.
Finding Clusters on a Map
Clusters are groups of neighboring geographies with similar measurements.
How to spot clusters: Look for a group of areas on the map with similar data points.
What clusters can reveal:
Population enclaves with similar experiences
Populations that are being exposed to similar conditions, such as a high concentration of opportunity or disadvantage
Identifying Islands on a Map
Islands, or spatial outliers, are areas that don't fit the pattern within a cluster.
How to spot islands: Look for geographies within a cluster that have noticeably different measurements.
What islands can reveal:
Islands can highlight the presence of unique circumstances or factors affecting a specific area.
Using more data, your local knowledge, or community outreach, you can build an idea of what conditions may be different there.
Alignment of Two Variables on a Bivariate Map
Alignment occurs when two variables follow similar spatial patterns.
How to spot alignment: Look for neutral colors that show up in the center of a bivariate map legend.
On the yellow – blue scale, look for shades of gray.
On the magenta – green scale, look for shades of purple.
What alignment can reveal: Alignment helps show how two factors, like income and access to transit, relate across areas within a community.
Division of Two Variables on a Map
Division shows stark contrasts between geographies based on two variables.
How to spot division: Look for areas where strong colors represent extremes in a bivariate map.
For the yellow – blue scale, look for strong yellows or blues.
For the magenta – green scale, look for strong magentas or greens.
What division can reveal: Division tells a story of how different parts of a region may have been shaped by historical or social factors.