This section outlines the iterative process of development used to produce Priestley’s Chart of Biography and New Chart of History in a data driven, procedural, way. of Biography and New Chart of History in a data driven, procedural, way. Priestley’s original charts were engraved using a common process and displayed along an identical chronological scale, but the organization of subject matter and the underlying data dynamics in the two charts are quite distinct.
Our spreadsheets contain the main data behind our interactive charts. The spreadsheet for the New Chart of History in some ways resembles the chart itself: each cell of the spreadsheet represents a geographic territory (vertical axis) in a specific year (horizontal axis). Names in the cells indicate which regimes were in power in those times and places. Special codes represent transitions in power. There are 178 rows (territories) and 3000 columns (years).
The cells within the dark green lines represent the Munguls, who ruled in Turky in Asia from 1219 - 1394 C.E. The cells highlighted in light green identify the Ilkanians, who ruled the same region from 1336 - 1385 C.E.
This image shows the same highlighted area from the spreadsheet in GIS (left) and in the map (right). The contiguous cells with the same values are merged into polygons that represent the geographical (vertical) and chronological (horizontal) dimensions of a given regime in the chart space.
From the spreadsheet (CSV), values are translated into ASCII (names to numbers). The ASCII file is read by Esri ArcMap and transformed a graphical representation.
Using Python and ArcPy, different transitions are created with codes that determine whether the split is diagonal or vertical. The split polygons are then dissolved into the corresponding regions. This is then saved and exported to JSON, which is the graphic format of the chart data used in our visualization.
The chart data is stored as distinct layers containing the regions, places, regimes, and event lines. Distinct symbology such as color and line weight emphasizes the different layers.
Here, you can see the finished product. The digital, procedurally created one looks a lot like the original.
The Chart of Biography was also created using a procedurally driven technique drawn on-the-fly using the D3 JavaScript Library.
Here you can see that Cantemer is listed in Priestley's Index as d. 1763. This indicates that he died in 1763.
We identified several unique cases, that drive the line symbology, based on the information that Priestley knew about each person. Then, using the information in the Index, we draw each person's life line on the chart accordingly.