Spatial knowledge develops in humans through three progressive stages including landmark knowledge, route knowledge and survey knowledge. The first one refers to the capacity of memorizing places in relation to an event, the second to developing the sense of ordered sequences of landmarks. The last and more progressed stage is the one where the knowledge embraces simultaneously more locations, their interrelations and allows for detouring, shortcutting and creative navigation. (Montello 1997).

Among the different visualising methods (e.g. sketch mapping, transect diagramming, participatory aerial photo-interpretation, relief modelling, mapping, etc.) used to spatially reproduce people’s knowledge, Participatory 3-D Modelling (P3DM) is the one which - by adding the vertical dimension and using simple communication means (colours, shapes and dimensions) - offers ample opportunities for surfacing “tacit” knowledge and for merging individual life-worlds.

One of the reasons that tacit knowledge is being surfaced during P3DM is that the relief model helps different elders reflect on their own knowledge and listen to each other. It makes tacit knowledge become coherent and identifiable for the holders of that knowledge. This can be missed using other techniques. It is the link between memory, land and maps which creates a particular focus.

Provided adequate facilitation, its 3-dimensional nature enhances discovery learning through sensorial (visual and tactile) experiences, stimulates confrontational feedback, which in turn promotes debate, and frequently generates shared knowledge in visible and “tangible” formats.  In addition, by providing a "bird's eye view", a relief model contributes to widen the participants’ evaluative frame of reference on spatially defined issues (e.g. dynamics of linked ecosystems, hydraulics of watersheds, boundary issues, etc.) thus stimulating active learning and analysis. In other words it helps understanding ecological and social dynamics which go beyond the cognitive boundaries of the individual.

Reproducing geo-referenced people’s knowledge in cartographic format i.e. fitting a “receiver-oriented” communication model or in other words, packaging a message like visualized people’s knowledge, to meet the frame of reference of the receiver (scientists, engineers, government officials, politicians, etc.) has proved to generate information which could place informal (community) and formal (scientists, government officials, consultants, etc.) knowledge at comparable levels, thus facilitating interaction, reciprocal learning and negotiation (Alcorn, 2000, 2001; Poole, 1995, 1998; Rambaldi & al., 2000)

PPGIS, PGIS and P3DM Virtual Library