A handheld computing device comprises a data processor configured to allocate a set of measurements of a wireless signal amongst partitions of a hierarchical multi-level partition space. Each level has a plurality of the partitions. Each partition has a respective numerical range, and the value of each allocated measurement is within one of the ranges. One of the measurements allocated to one of the partitions has a desired rank. This partition encompasses the range of all the partitions in the immediately lower level. Each partition in the immediately lower level has a desired resolution for the allocated measurements. The data processor sums the number of measurements allocated to each respective partition in the immediately lower level until the desired rank is obtained. The numerical range of the partition in this lower level that is associated with the desired rank comprises an estimate of a characteristic of the wireless signal.