The Data & How It Was Processed
The primary spatial data for this visualization is a digitized 1930s historical map of Beijing, sourced from wikimedia then through internet archive to produce in IIIF. Because historical maps from this era were not drawn to modern standards, the cleaning process required geometric correction. To process this, we used AllMaps to mask the map’s borders. This made the old map to approximate modern spatial proportions. Our contemporary comparison data is a standard OpenStreetMap vector basemap.
Tools and Techniques Used
We used a combination of spatial tools to bring this together. AllMaps was used to georeference the IIIF map using identifiable control points (like the corners of the Forbidden City and the Zhonghai). We then pulled that warped layer into ArcGIS Online via an XYZ tile URL to create a stable web map. Finally, we imported that web map into ArcGIS StoryMaps, specifically using the swipe block to overlay the past onto the present.
The Function of the Visualization
This visualization serves both an exploratory and explanatory function in our project. By sliding the swipe tool, users can actively explore the dramatic expansion of Beijing’s physical footprint over the last century. Analytically, it clearly trace how the ancient city walls were demolished and replaced almost perfectly by the modern 2nd Ring Road, or how dense, traditional hutong neighborhoods were paved over for modern commercial grid systems.
Styling and Clarity
To ensure the visualization is legible and accessible, we focused heavily on high contrast. We selected a muted, light-gray canvas basemap for the modern layer. This ensures that the warm yellow and sepia tones of the 1930s historical map pop sharply against the background, making the changing borders immediately obvious. This high-contrast approach also accommodates color vision deficiencies, as the distinction relies on stark light/dark values rather than complex color coding. The swipe tool itself eliminates the need for a complex legend, acting as an intuitive, self-explanatory interface.