Alignment of AG Online with the Archaeological Cadastre

Aligning the geographical data from Archaeology in Greece Online (AG Online) with that of the Archaeological Cadastre of the National Directorate of Monuments and Archives is a project that began in 2023. Its aim is to provide researchers with improved documentation and a unified map view that combines the results of fieldwork with official archaeological sites, protected areas and monuments.

Participants in the project were:

Véronique Chankowski, Rebecca Sweetman, Guillaume Biard, Γιώργος Μουρατίδης, Ελένη Γκαδόλου, Louis Mulot, Catherine Bouras for Chronique des fouilles en ligne/Archaeology in Greece Online.
Μαρία-Ξένη Γαρέζου, Χριστίνα Ρωμάνου, Νίκος Σύρρης, Θανάσης Δήμου for the Archaeological Cadastre.

Semantic interoperability (correlation of both data models)

AG Online uses a toponymic database that enables users  to search  the data and visualise it on a map, although it was not originally developed as Geographic Information System (GIS). It contains two types of geographical data: each entry is linked to  a modern place name, which may represent towns, villages, or ancient sites, as well as, whenever possible, the precise location of the sites explored. As a result, each report can be associated with two places and two sets of coordinates or geometries: the nearest toponym and the exact location of the recorded fieldwork.  To date, AG Online has more than 21,500 records and 37,220 toponyms, of which ca 700 represent archaeological sites.

The Archaeological Cadastre, on the other hand, documents and visualizes the extent of sites, areas and monuments protected by archaeological legislation across the territory through an open access WebGIS. It provides authoritative information on the  cultural heritage of Greece and access to the corresponding official documentation. At present, it includes more than 17,000 monuments, 3,400 archaeological and historical sites, 844 protection zones and 220 museums.

Whereas the two approaches appear similar at first glance, the relationship between the data is ultimately more complex. Both concepts are ontologically different, but complementary and for this reason it is so important to be able to visualize them on the same map. To support this, AG Online has been further developed with GIS capabilities. 

Technical interoperability (correlation of the two web applications)

The enhancement of the AG Online toponymic database with GIS functionnalities enables the geospatial correlation of data, i.e. based on spatial proximity. As a result, on a map view, the data on the layers will be visualised together as closest points or polygons to the site described in the report. The alignment allows users to explore the integrated data on different levels:

- Toponyms: Each toponym record displays its relationship with the corresponding data from the Archaeological Cadastre . These links are presented both in the record's information fields and o the interactive map, enabling users to identify nearby official archaeological sites, monuments and protected areas. 

Fig. 1 - Toponyme - 39382, Rodos, Rhodes - Δ.Δ. Ρόδου (in two parts) : in the first part, the “alignments” field lists the entities that are located within or in close proximity to the toponym, grouped by type. In the second part, the map simultaneously displays the geometry of the toponym together with the corresponding entities from the Archaeological Cadastre.

- Fieldwork records (fig. 2). In each report, the map displays the selected toponym (blue marker), the location of the fieldwork or site (green marker) and the boundaries of the corresponding archaeological site and/or protection zone (yellow and/or red polygon) as well as any associated monument (purple geometry). Displaying these datasets together allows users to assess their spatial relationships at a glance. 

Fig. 2 . – Report on Chora, Mykonos. : The map displays the selected toponym (blue marker), the location of the recorded fieldwork (green marker) and the corresponding geometries from the Archaeological Cadastre (yellow).

- in the search engine’s map view: the AG Online data can be viewd alongside the Archaeological Cadastre data directly within the search results map, allowing users to explore both datasets simultaneously. 

Fig. 3. – The map view of the search engine displays both AG Online report markers and the corresponding data from the Archaeological Cadastre.

Conversely, AG Online’s geospatial data is also available in the Archaeological Cadastre, as a dedicated WebGIS layer. The AG Online report markers (orange) include pop-up windows displaying information from AG Online, together with a link that directs users to the corresponding report. In the example below (fig. 4), the archaeological site of Minoa is shown in the Archaeological Cadastre WebGIS on a satellinte basemap. The map displays the site's boundary (yellow polygon) together with the locations of the associated AG  Online reports.

Fig. 4. – Satellite view of the archaeological site of Minoa in the Archaeological Cadastre. Information from both platforms is displayed on the same map.

The followint figure illustrates the geolocation tool used in the AG Online report editor (back-end) : users can see a selection of toponyms from a list while the map displays the corresponding polygons and points from the Archaeological Cadastre appear as additional spatial reference. These polygons ssist in accurately geolocating the report and they can be clicked to open the corresponding record in the Archaeological Cadastre WebGIS.

Fig. 5. – Geolocation tool in the record editor (back end). The map displays the availble toponym options (blue markers / polygons) alongside the corresponding data from the Archaeological Cadastre (yellow polygons).

The table below presents the results of these alignments in list form, showing the name of the entity in the archaeological register, the type of entity in the archaeological register, and the associated AG Online place name(s).