Tuesday, September 8, 2020

Deprecating TimeMap for Leaflet for type/hoard maps

At long last, I have decided to replace the TimeMap library that combined an OpenLayers map with the SIMILE Timeline widget. This library has been a part of OCRE (and other type corpora) since the earliest phase of the project (late 2012/early 2013) to display the geographic distribution of hoards related to a coin type, with a timeline of hoard closing dates. Scrolling through this timeline forces hoards to appear or disappear on the map. This form of visualization has a useful function in that it might show patterns of hoards appearing in particular locations in the same time period. However, most researchers want to see all of the hoards visible on the map at once by default, and there was no way to turn on or off the appearing and disappearing of findspots when scrolling the timeline.


TimeMap: only a few hoards visible at once for RRC 50/2.


RRC 50/2: all hoards are visible in Leaflet/GeoJSON


The GeoJSON for a coin type now includes Features for each hoard, conforming to Karl Grossner's GeoJSON-T extension for date ranges for the closing date. Ideally, I would like these closing dates to be represented as a histogram rather than a timeline, as demonstrated by a prototype of WebMaps-T here. This, I believe, is a more useful visualization of of the temporal distribution of coin types. WebMaps-T is not quite ready for production yet, but I have moved forward with deprecating TimeMap, replacing it with a Leaflet map that simply shows all hoards as points, without respect to their temporal component. This at least fulfills the primary research use case: showing all of the hoards simultaneously on the map.