1. A method, comprising: generating in a mobile wireless device, grid nodes representing one or more floor areas in an enclosed space, based on a map of the enclosed space; estimating in the mobile wireless device, locations along a path of motion of a user of the mobile wireless device traversing the one or more floor areas, based on motion observations made by a motion sensor in the mobile wireless device and map information; generating a radiomap of the one or more floor areas by making radio measurements with the mobile wireless device, at the estimated locations along the path of motion, and mapping the measurements to the generated grid nodes that are closest to the estimated locations; and compiling in the mobile wireless device, a fingerprint data structure of the radiomap, including observation elements representing the radio measurements at the mapped grid nodes.