Nomisma measurement analysis interface ready for wider testing

I have been working on and off for the last month or two on a new quantitative analysis feature in Nomisma, which is available on pages for certain types of Concepts (that are associated with coin types that have been ingested into Nomisma) as well as on a new page, http://nomisma.org/research/metrical.

Much like the distribution analysis interface, the user can select multiple dataset groupings to compare for average weight or average diameter. Optionally, and like the existing features in OCRE, CRRO, and PELLA, the user can input a start date and end date and an interval of 5 or 10 years in order to visualize the change in average weights over time. The parameters established in the web form are used to query a web service, which interacts with Nomisma's SPARQL endpoint and serializes the response into JSON for visualization.

Average weight of denarius (red), aureus (yellow), and antoninianus (blue) from 100 BC to AD 300. See for yourself.

What separates this interface from the feature that is built into Numishare projects (like OCRE) is that the weights are drawn from all relevant coins, regardless of an explicit connection to a coin type defined by a URI published by OCRE or similar project. This means that coins from Antike Fundmuenzen Europa or other finds databases that do not have positively identifiable RIC numbers can be queried alongside those that do, as long as those relatively uncertain coins still have some certain attributes, such as authority or denomination. Moreover, these interfaces allow the querying across related, but separate datasets--e.g., to evaluate the change in average weight of denarii from 100 B.C. to A.D. 100, even though the denarius coin types are split between OCRE and CRRO starting about 27 B.C.

The raw data can be downloaded as CSV for further analysis, visualization, or publication, and the chart for the metrical analysis page can be reproduced easily by bookmarking the resulting URL.

Weight of Augustan denarii from Rome compared to Lugdunum

Known Limitations

The metrical analysis feature is still a working proof of concept that will be refined and enhanced over time.

First, we do encounter coins that are either cataloged with the wrong RIC number or the automated matching script erroneously interprets a reference into the wrong RIC number, so the weights of these coins may have an effect on the overall average for a query. I think, in most cases, the margin of error is quite small.

The charts are visualized with a d3.js plugin called d3plus. There's an error in the handling of BC dates (according to the ISO spec), and so (in interval queries), the dates are converted to an integer value. So -100 is 100 B.C. and 200 is A.D. 200. As a result, the d3plus line graph cannot be set as a timeline, and therefore date ranges that do not contain weight data are removed from the chart. It is important to be able to visualize gaps in weights, as these gaps may illustrate periods where coin types conforming to a query were not issued (for example, there is no weight data for aurei from 70-50 B.C.).

One last thing to note is that I have not been able to manually override the x-axis labels, so -100 actually means 100 B.C. to 96 B.C. when the interval is set to five years (not just 100 B.C.). The human readable date range is still available when hovering the mouse over a point in the chart and in the CSV download.

Next Items

Aside from minor alterations that should come when d3plus's B.C. date glitch is fixed, I plan to expand beyond average weight and diameter to showing weight+diameter as a cluster as well as standard deviation for measurements, which should be more illustrative of coins that do not conform with the norm, enabling them to be eliminated from further weight query, while also flagging them to collections as potentially erroneously attributed coins, counterfeits, partial specimens, or other such aberrations.

Extending Nomisma geoJSON for Temporal Data

The geoJSON output for queries for findspots and hoards associated with Nomisma.org concepts has been updated with the geoJSON-T extension, including closing or burial dates of hoards or individual finds, when known. Additionally, the properties following the geoJSON-T proposed model for gazetteer toponyms and URIs, e.g.:

{
      "type": "Feature",
      "label": "Meolo (Albaredo d'Adige) (Italy; ME2)",
      "id": "http://numismatics.org/chrr/id/ME2",
      "geometry": {
        "type": "Point",
        "coordinates": [
          11.27843,
          45.31859
        ]
      },
      "when": {
        "timespans": [
          {
            "start": "-0038",
            "end": "-0038"
          }
        ]
      },
      "properties": {
        "toponym": "Albaredo d'Adige (Italy)",
        "gazetteer_label": "Albaredo d'Adige (Italy)",
        "gazetteer_uri": "http://www.geonames.org/3183350/",
        "type": "hoard"
      }
    }

Furthermore, the getFindspots, getHoards, and heatmap APIs have been updated to accept a coinType request parameter instead of an id parameter in order to get relevant geographic data associated with coin type URIs, rather than associations with Nomisma-defined numismatic concepts. This is the first step in the eventual overhaul of the mapping features in Numishare coin type projects (like OCRE) to render geoJSON-T in Leaflet, finally retiring the TimeMap plugin that has not seen active development in at least four years.

KENOM project joins Nomisma/OCRE

The KENOM project, a consortium of 13 German institutions contributing into a central numismatic portal, has been integrated into Nomisma.org. More than 4,500 Roman Imperial coins from three institutions (The State Coin Collection of Munich, the Coin Cabinet of the University of Goettingen, and Thuringian Museum for Pre- and Early History) have been made available Online Coins of the Roman Empire. All of these coins have been photographed at a high resolution and are published following the IIIF specification, which are treated as zoomable images in OCRE, and will eventually be useful for more sophisticated iconographic annotation.

Augustus 171A

Below is a fuller description of KENOM:

KENOM (Kooperative Erschließung und Nutzung der Objektdaten von Münzsammlungen) is a long time project of different numismatic collections in Germany to bring their numismatic objects (coins, medals, paper money and also coin find-informations) together online. There are a common internal database of the project for the data input and a portal of presentation of qualified data and images. Goals of KENOM are the harmonisation of numismatic data of the partners, the integration of open linked norm data and the definition and use of a LIDO-based data exchange format. 2012-2015 the project was funded by the Deutsche Forschungsgemeinschaft, now KENOM is operated jointly. The strong technical partner of the project is the Gemeinsamer Bibliotheksverbund Göttingen. Today already 13 institutions present more than 33,000 numismatic objects together in the portal <http://www.kenom.de/>.

KENOM has developed lookup mechanisms that read OCRE and CRRO web services, making it easy for curators to link their collections directly to these Linked Open Data systems. The RDF data for OCRE were harvested from KENOM's OAI-PMH using a PHP script I put together yesterday afternoon. Project coordinator, Mario Schlapke, plans to write a more comprehensive post about the process of integrating KENOM with the wider ancient world linked data cloud.