Abstract
In case of emergency, slow or obstructed communication lines may make exchange of information difficult or even impossible. Such a problem is particularly important when we manage maps, which are usually complex to deal with. They require a long time for transmission and can generally be viewed only after complete acquisition. In order to mitigate this issue, a promising approach is to transmit a reduced map first and, in subsequent steps, its progressive refinements until reaching an acceptable detail. However, choosing the first and the subsequent reduction levels is a complex problem and users are often let to decide on a case-by-case basis. In this paper, we present an empirical experiment we performed to determine which reduction levels we should apply in case of emergency by analyzing the perception of map changes with respect to the original map. On the basis of such results, we also derived a set of rules that allow us to determine appropriate reduction levels on the basis of the number of vertices and the number of polygons.