If vector and raster data describe how geographic information is represented, layers and projects describe how that information is organized and brought together.

A GIS project is not a single map. You might produce maps or other visualizations with a GIS, but it is better to think of a GIS project as a collection of spatial layers, stacked, ordered, symbolized, and aligned within a shared coordinate system. These layers can be turned on and off and put into conversation with one another for analysis. What we see on the screen at any moment is the composite result of multiple spatial claims rendered together.

This layered structure is foundational to GIS thinking.

Thinking in Layers

Each layer represents a particular kind of spatial information:

• A base layer (e.g., OpenStreetMap or satellite imagery) provides contemporary geographic reference
• A vector layer might contain locations extracted from a literary text
• A raster layer might display a georeferenced historical map
• Another layer might represent environmental conditions (e.g., historical sea ice extent)
• Additional layers may encode thematic or interpretive information.

Layers can be turned on and off, reordered, styled differently, or queried independently. The “map” is not a fixed image; it is a dynamic arrangement.

Example: The Frankenstein Atlas

The Frankenstein Atlas project illustrates how layering becomes interpretive. We’ve mentioned this project a few times already and will return to it in the next chapter for our walkthrough. Here let us consider just a few of the possible layers involved:

• A base map providing modern geographic reference
• A vector point layer constructed from geographic locations mentioned in Mary Shelley’s Frankenstein with an accompanying attribute table containing textual excerpts, chapter references, and thematic coding such as a field where the project attempted to capture the influence of Edmund Burke’s aesthetics on Mary Shelley’s Frankenstein in order to produce an “aesthetic geography of the sublime and beautiful” by encoding places associated with these notions
• A layer representing historical ice-edge data in the Arctic.
• Historical records (e.g., ship captains’ logs and maritime narratives) used to estimate where Walton’s ship might realistically have traveled
• A georeferenced historical map of Edinburgh or Geneva, allowing comparison between past and present spatial imaginaries

Each of these layers represents a different kind of knowledge. Literary description. Environmental science. Historical cartography. Thematic interpretation. When assembled together, they allow new questions to emerge: Could Walton have reached the location Shelley implies, given historical ice conditions? How does Shelley’s aesthetic geography relate to elevation, landscape, wilderness? How does 18th-century Edinburgh differ spatially from the modern city used as a reference?

Layering makes juxtaposition possible.