Historic and archaeological sites

This paper stems from the project "Gestion du patrimoine culturel de la Tunisie" for the setting up of a first nucleus of computerised data on the historical and archaeological heritage starting with the reconnaissance of protected monuments in the whole country. The standard graphic catalogues used are those established by the Council of Europe. The work started in September 1997: a year later the data is in the process of being organised for filing and the production of a computer data bank supported by a geographic information system. 300 sites have been visited and catalogued for a total of about 1,000 monuments with about 10,000 photos taken and 2,500 images of archival origin (historical photos, maps, cartography, aerial photos, basic texts etc.) for a total of 100 CD ROMs. A paper library composed of three hundred dossiers, one for each site, will be consigned to the Tunisian Cultural Ministry, and an easy-to-use electronic data bank (schedules, photos and maps) for the management of the historic-archaeological heritage inventory.

Tunisia. Sbeitla (Sufetula). Rear of the Capitolium (2nd quarter of the 2nd century ad.). Catalogue photo.

Products used and form of data

The activity of loading data, both graphical and alphanumeric types, is carried out with the following I.T. tools:

• Access - is used to load all the alphanumeric data, relating to survey schedules, in table form arranged according to a pre-defined layout.
• Autocad - is used to produce any geometric type data bank.
• ArcView - is used to create the data banks of the geography information system (GIS) for historical and artistic assets.

Creation of the tables

The alphanumeric tables are the fruit of a data entry activity directly linked to the descriptive schedules made during the survey of the cultural assets in the territory. The file produced is structured so as to guarantee any type of logical relationship in the project, and in particular, permits linkage between the various data bases with the relevant drawn subjects.

Creation of the cartography

The survey and the correct placing of the items which are cultural assets require the subdivision of the cartographic elements into two categories which are:

• Raster cartography
  For the moment it is composed of 12 maps transposed to a scale of 1:200,000 and acquired in grey tones with a detail of 800 dpi subsequently memorized to 150 dpi.
  Raster cartography is set within the cartographic reference system U.T.M. (Mercatore).
• Administrative type vectorial cartography
  The administrative type vectorial cartography is integrated superimposing itself to the raster cartography, with which it forms the cartographic plan of the territory.
  The vectorial cartography which constitutes our T.I.S. is subdivided into:
• Administrative cartography.
  The administrative cartography is represented by both area and point type elements where:
  • the area elements locate the boundary marks of the State and Governorat administrative confines;
  • the point elements locate the texts which describe the toponyms in the map-drawing.

Tunisia. Map on a scale of 1/200.000 coded in grey tones and oriented to cardinal points.

Cartography of the cultural heritages

The administrative cartography is represented by both area and point elements where:

1. "Site" boundary.
2. It is a "fictitious" representation of the boundary which encloses all the complexes and monuments which are contained within a site. The real boundary not being available, it is represented in conventional way by a rectangular window which includes all the elements contained in the site.
3. "Complex" boundary.
4. It is always found within a site and is materialised by its perimeter; this area encloses all the monuments which have similar characteristics, or in any case referable to a single logical entity.
5. Selection of the "monument".

It is a representation of the monument based on its position in the site.

A. Databases produced and relative relationships

The "site", "ensemble" and "monument" cards are primary schedules and identify univocally the objects surveyed and recorded in cartographic form.
Each one of these objects can have further descriptive type information and this is recorded in other tables (sub-schedules) linked to the main table via logical type relationships. The sub-schedule "Documentation" indicates the documents which are associated with each type of main table; specifically: archives, bibliographies, drawings and photos (fiches). All the tables forming part of the alphanumeric database, where it has been possible to carry out normalizations, have restricted the compilation of information to a series of pre-defined words (dictionaries)

Creation of the files

The territorial information system is created by utilizing all the files: graphs and tables, generated during the data loading activity. The possibility of utilising a cartography which is perfectly geo-referenced and in absolute co-ordinates makes it possible to obtain a work base transposed in 1:1 scale, after allowing for errors arising from the precision of the acquisition maps. This situation allows us to operate in an absolutely free manner knowing that for any type of operation carried out on this cartographic system, distances and measurements are utilised which approach absolute and real values.

B. Application product

Consultation of the data

The most evaluative aspect of an information system is given by the possibility that a not particularly expert operator has of carrying out consultation operations on the data making up the various files. This occurs in a two-directional way, and has as its points of departure either the databases or the map-drawings, without distinction. The result of the interrogation, in both cases displays both the database records and the relevant graphic objects, guaranteeing the inheritability of the information between the different themes for spatial type inquiries.

Graphic consultation

For an information system to be defined as being correct and efficient it must be able to carry out both easy and complex consultation operations; with this objective we have utilised a cartographic system which must, necessarily, be a vectorial type, and structured according to a logical criterion. In fact all the objects which must make up the information system have been identified; they have been grouped according to themes, each of which represents a single and logical category of elements. The various themes, which make up the graphic data bank, have a hierarchical type logical sequence where an object contains others of an inferior category. This type of structure makes it possible to manage integrated relationships between the various cartographic themes activating the recognition of the various geometric congruences guaranteeing the inheritability of the information between the different themes, for spatial type inquiries. Graphic consultation is done by selecting one or more graphic elements on the video. In this way it is possible to carry out consultation of all the alphanumeric schedules which refer to the selected graphic objects. The graphic selections occur in the following ways:

• by selecting one single object at a time,
• by individualising all the chosen objects present inside a selected window.

Tunisia. Mausoleum of the Emperors Flavius (middle of the 2nd century ad.). Catalogue photo.

Alphanumeric consultation

Through the use of inquiries (query), alphanumeric consultation makes it possible to carry out filter operations on a single database, with the aim of individualising the elements corresponding to the characteristics which were the subject of the interrogation. An application may activate this filter process in the following ways:

• making inquiries on totally guided search routes.
• making inquiries on partially free search routes.

Guided routes

An application utilises a graphic and alphanumeric data bank with files generated with standardised characteristics. In the programming phase this permits the activation of pre-defined search programmes where the interrogations are the fruit of obliged choices both in terms of graphical elements and descriptive characteristics on which the filter operations are carried out according to the searches effected. These functions permit the execution of research operations, also by not particularly expert users, in a rapid and safe manner.

Partially free interrogations

The application continues to have a series of interrogation routes which are conditioned to guided types of research but, at the same time, is able to carry out searches of a free type activating the SQL language in an intelligent manner. This method allows us to make connections between tables which don't respond to any standard requisite, with those in the system which instead respond to the normalisation requisites of the system.

Management of associated documents

For each element surveyed during the scheduling activity, photographs are taken which give a correct and real vision of the registered objects.

These photographs are taken from various points of view and aim at describing the elements showing up the most important characteristics and particularities.

An alphanumeric schedule is compiled for each photo, arranged in fields, with the main characteristics indicated; the matching of the photo with the relative schedules is carried out by the operator in an interactive way with reference to the information shown by the surveyor and the photographer.

Tunisia. Mausoleum of the Emperors Flavius (middle of the 2nd century ad.)
Detail of epigraph to Titus Flavius Secundus. Catalogue photo.

C. Application characteristics

Maintaining the above-mentioned formats and data structures unaltered, interfacing ArcView with access becomes essential, as an initial operation; this makes the alphanumeric data bank immediately available to the Territorial Information System (T.I.S.), keeping the relationships which guarantee the crossed-over visibility of the data unaltered.

The access database is in fact composed of a series of alphanumeric tables sub-divided into three parts (Site, Ensemble and Monument). These tables are structured in order to guarantee a series of logical relationships with the aim of ensuring the inheritability of common information.

The cartography is composed of:

• a series of raster themes, which constitute the cartographic base;
• a series of vectorial themes which identify the elements which may be interrogated and characterised.

Every cartographic object is associated with an identification key which permits its individualisation and the relative linking with the table structure to which it refers.

Tunisia. Mausoleum of the Emperors Flavius (middle of the 2nd century ad.)
Detail of epigraph to Titus Flavius Secundus. Catalogue photo.

The relationship between the table and the relative graphic objects is made through linking operations which from time to time have to guarantee the visualisation of the various schedule/graphic representations. In addition, it is necessary to activate minimum and maximum visualisation factors for each of the cartographic themes which form part of the T.I.S. in order to guarantee permanent correct visibility. The application product must permit the following operations:

• interrogate the selected theme database and obtaining as a graphic result the characterisation of the located elements.
• select on the video one or more graphic objects and as a result obtain the individualisation of the relative schedules present inside the alphanumeric tables.
• map-drawings forming part of the cartography,
• carry out free inquiries on the various schedules of the alphanumeric database.

Singling out one or more cartographic objects forming part of the same theme makes it possible, through the utilization of a series of personalised buttons, to activate the following consultations:

• cartographic, which must be perfectly visualised inside its video area, inserting all the elements which have been singled out in the selection phase.
• attached items, such as photographs taken during the survey,
• captions,
• alphanumeric schedules,
• documentary sources, that is, raster images of any historic document found during the survey.