1. A method comprising: positioning a target object in a wireless communication environment, said positioning comprising performing the following acts on a set of at least one positioning server: 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 and using the set of relevance indicators for determining two or more predetermined sets of relevant sample points for each value within the set of expected values of at least one of the physical quantities, wherein the two or more sets of relevant sample points are subsets of the sample points in the data model; storing the predetermined sets of relevant sample points and using them in several positioning cycles, wherein each positioning cycle comprises: receiving 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 which comprises sample points concurrently relevant to all the observations made at the target object's location within the current positioning cycle at the target object's location; and 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.