Trésor is a computer project carried out within the framework of the Towards project, whose aim is to allow the collective and interactive conception of digital maps. Trésor is not strictly speaking a software but a series of links between different existing softwares, of which it extends the functionalities.
One distinguishes three important layers for Trésor :
1/ The data layer, which uses a software able to connect itself to several GIS databases and to link their information. (Map Bender)
2/ The rich vector editor layer, which uses a vector drawing software able to upgrade its functionalities through plugins and that allows the production of maps in a format adapted to the printing and to Web exports. (Inkscape)
3/ The Web viewer editor layer, which uses the functionalities of Web browsers. (Firefox, Openlayers)
Thus, the users of Trésor will be able to work on a map from their vector drawing software, to get precise geographic data and to apply transformations or projections. The result can be printed in high definition or shared on the Web, where other persons will have the possibility to edit the map or to contribute to it thanks to a Web interface easily accessible. All the components of Trésor are distributed under free licenses.
The creation of a software also brings with it the question of classification (notably the way in which cartographic data is entered on the on-line service), however with an additional difficulty: the difficulty of the interaction and superposition of maps that have a variety of degrees of subjectivity and of systems of coordinates, the interest being their intercommunication. Maps may indeed represent the same territory to very different scales and at very different moments. And the same is true for two objects, which may be physically far away from each other and still mentally close. Consequently, how to connect and to intermingle maps that have different spatial, temporal or mental projections? It would be possible to connect them by defining the transverse elements between the maps, i.e. common features or zones of reference. But this spatial world that is divided between several maps tears when there is no correspondence left. How to manage that tear, which is for that matter interesting? And would it be possible to deform those maps in order to create new correspondences? In that case, which map would serve as a frame? Would it have to be spatially referenced?
In order to exchange information and to connect creativities, the first idea was to set up an infrastructure of map data service that would speak to the artistic, activist, associative and cultural sector of Brussels, but also – why not? – to the public. However, as underlined by Benjamin Henrion during sessions of cartographic work, most software that give access to geospatial data are not free and the majority of current maps are subject to strict conditions of copyright, which restricts their collective use. So as to allow the traffic of maps, their production, their use, their transformation and their exchange, it has consequently always been clear that the cartographical instrument of the TOWARDS project might be developed and provided as a free software and that the data that would result would submit to the standards of diffusion governed by the principle of copyleft.
But even though most participants agreed on the need to maximize the collaborative potentialities of the instrument, others on the other hand raised objections as regards the sharing out of the data… Anne-Lise Dehée, who works on a project of “therapeutic maps” with women living on the street (homeless persons, drug addicts, prostitutes…), insisted that it was crucial to find a subtle balance between what is revealed and what remains hidden… According to her, it is about avoiding that non-legal or private cartographical data be used as means of control or of repression. Which are therefore the conditions for the public use of such a software? How is the data made accessible? How can I, as a contributor, be in control of my data? How to protect it, how to divulge it, to conceal it? Technically, how to make a software that allows carrying out such operations?
During the sessions of cartographic work, the participants were invited to think about the specifications that were necessary to the making of that software as well as about the working and the visual aspect of its interface. The thinking over was assigned to four groups.
The first one dealt with the particular calculation functionalities that were necessary to the production of maps (projection, distortion) and with how these might be openly accessible through a visual interface. How does an interface give access to the different subjective approaches that share the same set of reference coordinates? How to visualize the different views of one single map?
The second group looked into the question of the existing free instruments for the management of geographical data, into the standard formats necessary to stabilize the exchanges between the applications. A particular attention was paid to the SVG format, which allows a vectorial picture processing and which corresponds to the need of precision of cartographers as well as to the flexibility that is necessary to artistic creations.
The third group was in charge of the types of representations required by subjective cartography and more specifically of the relationships between perceptible geographical data and temporal data. How to cross axes of different types and which play with spatial and time scales?
The fourth group refined the questions of metadata, i.e. the contextual information necessary to read the map. How to clarify the protocol that has been used to design the map? How do legends interact with image? How do maps become instruments of narration as well as spatialization?
The considerations of the various groups have led to an astonishing amount of diagrams, sketches, recommendations and suggestions, comments and wish-lists that guide the technical elaboration of the software in hand.