1. A method for positioning a target object in a wireless communication environment, the method comprising: maintaining a data model for a plurality of sample points, each sample point comprising a sample location and a set of expected values for one or more physical quantities at that sample point; maintaining a set of relevance indicators for indicating one or more sets of relevant sample points, wherein the one or more sets of relevant sample points are subsets of the sample points in the data model; making observations of at least one of the physical quantities at the target object's location; based on the observations at the target object's location and the set of relevance indicators, determining a current set of relevant sample points; estimating the target object's location based on the observations at the target object's location and on the current set of relevant sample points; whereby sample points not included in the current set of relevant sample points can be omitted from said estimating step.