A method and apparatus for collecting data for detecting and locating disturbances. A plurality of distinct regions of the space are identified, and, preferably, a hand-held device adapted for sensing positions of the device and respective representations of a field parameter at the positions is used. The positions are quantized within the regions and the corresponding representations within a region are combined. Separate scans are used to obtain baseline and detection scan results corresponding to the regions. The baseline and detection scan results are compared within a region, and the results of the comparison are used to produce scan results from which can be discerned whether a disturbance has occurred within the region. A triangulation is performed for determining the location of the disturbance, preferably using combinations of indeterminate sets of the scan results.