This article focuses on Participatory 3-D Modelling (P3-DM), a tool which merges Geographic Information System (GIS)-generated data and peoples' knowledge to produce a stand-alone relief model. P3-DM was used in the Philippines, by the National Integrated Protected Areas Programme (NIPAP), to give due weight to the interests of local communities in delineating protected area boundaries, identifying resource-use zones and formulating policies on protected area management. The model provides an efficient, user-friendly and relatively accurate spatial research, planning and management tool. Regular updating of the model allows for monitoring change and for integrating time into the system. By combining 3-D models with GIS, it is possible to implement (participatory) monitoring and evaluation over large areas. The article explores the process and the lessons learned.