Participatory texture documentation (PTD) is a geospatial data collection process in which a group of users (dedicated individuals and/or general public) with camera-equipped mobile phones participate in collaborative collection of urban texture information. PTD enables inexpensive, scalable and high resolution data collection for urban texture mapping. In this paper, we introduce GeoSIM (Geospatial Social Image Mapping), a system we have designed and developed to enable efficient PTD. GeoSIM deploys a two-step planning process for efficient PTD. At the first step, termed "viewpoint selection", a minimum number of points in the urban environment are selected from which the texture of the entire urban environment (the part accessible to cameras) can be collected/captured. At the second step, called "viewpoint assignment", the selected viewpoints are assigned to the participating users such that given a limited number of users with various user constraints (e.g., spe...