Geographical information retrieval - finishing touches

In my last post back in July I wrote about the development of a set of APIs and an interface for geographically querying historical places and their annotations, which allows users to browse a long lost territory and retrieve information about historical artefacts. However, even an application as simple as a map visualisation wouldn't be possible, if services, data, and tools weren't made available to the community by a number of different parties. Naming all those upon whose work I have built is no easy thing. But the following have been especially helpful:

• Provinces' polygons from Depauw University
• Historical tile sets from Regnum Francorum Online (kudos to Johan Åhlfeldt)
• Pelagios API (kudos to Rainer Simon)
• Pleiades project for providing the coordinates of the historical places (kudos to Sein Gillies)
• The Javascript library Ancient World Linked Data (awld) from the Institute for the Study of the Ancient World at New York University
• OpenLayers API
• CartoDB
• Heatmap.js

Even this short list gives a measure of the collaborative nature of research and development in this area. I owe a debt of gratitude to all of those who have provided the above resources and obviously to all of those who enabled them to do so. Below I go into a bit more detail about my finishing touches to the interface for retrieving geographical information about the ancient world. But, for those of you impatient to see the result, you can go straight to the heat map by clicking here.

Correction of box annotations

A few corrections have been made on the annotation API in order to return only annotations for which the actual geographical context was a point. It was in fact made known to me, thanks to Leif Isaksen, that in many maps the heat spots were strangely clustered at the intersection of nodes in a grid.    

Grid effect on heat spots

The effect is quite clear when visiting a province like XI, in Italy, where the spots are seen clearly positioned in an organised grid. Not only. It seems in fact that for regions like these, the majority of the annotations are grouped in this way. Clearly, the presence of numerous annotations like these undermine the purpose of having a heat map in the first place since the information about the original place associated to an annotation is lost and the contribution from the precise annotations is somewhat shadowed.

For this reasons all annotations whose geographical context is not a point has been ruled out as contributors for the final heath map, obtaining as a result a more informative map where hot spots are grouped around historical settlements like in the figure below.

Heat map without box annotations

Integration of Historical tile sets

An interesting addition to the interface is the adoption of a particular tile set for historical regions developed by Johan Åhlfeldt in his project Regnum Francorum Online (a description of his work can be read in this blog here). The tile set allows users to provide a background for historical maps which includes names of ancients settlements and depicts also well known roman roads (like the Appian way) alongside known mines and sanctuaries.

Seeing the actual historical landscape with the original names and connections among settlements can only increase the allure of exploring archaeological artifacts and in fact provides the best context in which to put what can be accessed via the different APIs from the Pelagios data galaxy.

This work has been supported by Pelagios and I'd like to thank Leif Isaksen, Elton Barker, Rainer Simon and Johan Åhlfeldt for sharing their ideas, support and resources.

Gianluca Correndo
Research fellow WAIS group Electronic and Computer Science University of Southampton