Data base

The data base used by the system is different from the similar ones used in many other cartographic systems because of its archaeological destination. In the data base there is information for two different types of objects - geographical and archaeological. Everyone of them has its features and is represented with both spatial ana aspatial information. The spatial information is a set of coordinates of points in Cartesian system. Aspatial is all other infor­

mation, which is in relation to defined spatial data, but itself it has no positional meaning. The aspatial informa­

tion is stored in the data base as relations, the spatial - with the coordinates of representing points.

In the data base there are entities for geometric and cartographic elements. The way of representation of these elements is described below.

Geometric elements:

- point - with x,y,z coordinates.

points x,y,z and a,b,c.

- curve - with coordinates of a set of points put in order.

- circle - with radius

x,y,z - centre coordinates a,b,c - normal véctor.

- plane - with x,y,z - coordinates of a pass point, and a,b,c - normal vector.

- polygon in a plane - with one or a few connected curved lines, representing its boundary.

Cartographic elements, representing geographical and archaeological objects:

- interpreted as points.

They are depicted with figures centred with the

corresponding points. The sizes and forms of these figures presented some of the aspatial information associated with

the treated cartographic or archaeological objects. Such objects are summits, towns and villages, archaeological centres and so on. In the data base the information kept for such objects consists of the type, specifying the real object, its name, and a pointer to the coordinates of the representing point.

- depicted with lines.

These are rivers, roads, railroads, canals, transmi­

ssion lines and etc. The type of line with which such car­

tographic element is depicted shows the essential informa­

tion for the respective real geographical or archaeological object. In the data base for such element there is informa­

tion for the substance of the real object, its name, and a

pointer to the set of points representing it.

- regions.

These are districts, lakes, orchards, vineyards,woÖd­

land and etc. They are depicted with their boundaries and the way of shading, if any, shows the type of the represen­

ted real object and some of the aspatial information associ­

ated with it. The necessary information for such object is the type and name of the real object, and one or more poin­

ters to the set of points representing it.

3. Data input

We used a subsystem, which makes an incoming control and initial processing of the input data, after which the information is stored in the data base.

For input of the non-positional information we useü the keyboard of the computer, and for the positional we have two ways - the keyboard and the digitizer. The x,y coordi­

nates of spatial data from the existing maps are received with the digitizer, while the third coordinate z - altitude

above sea level - is typed on the keyooard. Its value is the value of horizontal line passing through the digitizing

point. The information for the point elements is stored in the data base without further processing. For the linear and polygon elements we used a subroutine for reducing the num­

ber of representing points in XY plane, as the allowable tolerance, which specifies how much the precision of the representation should be relaxed, is given by the user.

After this the data is stored in the data base.

For the cases of making plans of small areas the posi­

tional information is entered from the keyboard of the

tie terrain of the archaeological object. Because of the small sizes of the investigated area it is not necessary to use some special cartographic projection. All the coordi­

nates are in Cartesian system. For centre of the system is used an arbitrary, non-change able object on the terrain.

The sequence of defining the elements is interactive and the user can change the representation of some parts of the visualized element. For representation of linear and polygon elements are used sets with different number of

points, as the connection of points is with segments or with smooth curved lines passing through the points. The way of connection depends on the nature of the objects. If such received picture of the linear or polygon element differs from the form of the real object, new points are taken and the interpolation is done, again. The procedure is repeated until the drawn image is satisfactory. After that the infor­

mation is stored in the data base.

For indicating the archaeological finds is used a set of beforehand defined figures, as the set can be changed.

Any of the figures in the set can be changed or deleted, and new figures can be added. The representation of the new fi­

gures is given by the user with the help of the graphic cur­

sor or digitizer. The data for every graphic figure is stored in the aata base as a structure and when this figure is de­

picted the information from the structure is modified accor­

ding to the desired scale.