Mitchell Chapter 5 — Finding What’s Inside

Why map what’s inside?

People map what’s inside an area to monitor what’s occurring inside it, or to compare several areas based on what’s inside each.

This lets people know whether to take action and lets people compare areas to see where there’s more and less of something.

Defining your analysis

1. Number of areas

• Single area:

A service area around a central facility, such as a library district.

– A buffer that defines a distance around some feature.

– An administrative or natural boundary.

– An area drawn manually.

• Multiple areas

– Contiguous, such as ZIP codes or watersheds.

– Disjunct, such as state parks.

– Nested.

2. Type of features inside the areas

• Discrete

– Unique, identifiable features that can be listed or counted or summarized by a

numeric attribute associated with them.

– They are locations (addresses) or linear features (streams, roads).

• Continuous

– Seamless geographic phenomena.

– Spatially continuous categories or classes (vegetation type, elevation range).

– Continuous values: numeric values that keep varying (temperature, precipitation).