Abstract : This article investigates the practice of participative mapping by examining the creation of a geographic database on infrastructure for bicycles. Based on the exploration of OpenStreetMap discussions, the authors draw up an inventory of problems that amateur cartographers encounter with regard to description. Prior to the stabilization of categories, the contributors' doubts reveal an elusive urban infrastructure that contrasts with the system which is ordered and structured by policies. These doubts crystallize around three levels of resistance to the creation of a database: first, in discussions, infrastructure for bicycles seems to be heterogeneous and changing; second, it is already organized in versions that are difficult to link up to one another; and, third, it is actualized in users' practices that are difficult to break away from. By limiting the analysis to problems of description, this article highlights a particular aspect of the contributors' experience: collective inquiry at its most open. In parallel with a perspective that favours agreement, the role of procedures in debates, or the contributors' motivation, this approach serves to document the phase of doubt and trial characterizing exploration as such, before order is established.