A method comprising: providing a plurality of location anchor transceivers (276, 278) and a plurality of enhanced location anchor transceivers (900, 902) operating from respective predetermined locations within a region; a portable transceiver within the region detecting and measuring a signal parameter of a signal from at least some of the plurality of location anchor transceivers and enhanced location anchor transceivers; a location engine calculating an estimated location of the portable transceiver based upon the signal measurements of the portable transceiver and the respective predetermined locations of the plurality of location anchor transceivers and enhanced location anchor transceivers; at least some of the plurality of enhanced location anchor transceivers detecting and measuring a signal parameter of a signal from at least some of the plurality of location anchor transceivers and other enhanced location anchor transceivers; at least some of the plurality of location anchor transceivers, the enhanced location anchor transceivers and portable device transmitting the measured signal parameters to a location measurement module; the location engine, being in a location manager module, calculating an estimated location of the at least some of the plurality of enhanced location anchor transceivers based upon the signal measurements of the at least some of the enhanced location anchor transceivers and the respective predetermined locations of the plurality of location anchor transceivers and enhanced location anchor transceivers; calculating a location error for the at least some of the plurality of enhanced location anchor transceivers based upon the estimated location and predetermined location of the enhanced location anchor transceiver; and characterising in displaying at the location manager module an estimated error of the estimated location of the portable transceiver based upon the calculated location error of at least some of the plurality of enhanced location anchor transceivers that are nearest the estimated location of the portable transceiver; further characterised in that the enhanced location anchor transceivers include gas concentration detectors. providing a plurality of location anchor transceivers (276, 278) and a plurality of enhanced location anchor transceivers (900, 902) operating from respective predetermined locations within a region; a portable transceiver within the region detecting and measuring a signal parameter of a signal from at least some of the plurality of location anchor transceivers and enhanced location anchor transceivers; a location engine calculating an estimated location of the portable transceiver based upon the signal measurements of the portable transceiver and the respective predetermined locations of the plurality of location anchor transceivers and enhanced location anchor transceivers; at least some of the plurality of enhanced location anchor transceivers detecting and measuring a signal parameter of a signal from at least some of the plurality of location anchor transceivers and other enhanced location anchor transceivers; at least some of the plurality of location anchor transceivers, the enhanced location anchor transceivers and portable device transmitting the measured signal parameters to a location measurement module; the location engine, being in a location manager module, calculating an estimated location of the at least some of the plurality of enhanced location anchor transceivers based upon the signal measurements of the at least some of the enhanced location anchor transceivers and the respective predetermined locations of the plurality of location anchor transceivers and enhanced location anchor transceivers; calculating a location error for the at least some of the plurality of enhanced location anchor transceivers based upon the estimated location and predetermined location of the enhanced location anchor transceiver; and characterising in displaying at the location manager module an estimated error of the estimated location of the portable transceiver based upon the calculated location error of at least some of the plurality of enhanced location anchor transceivers that are nearest the estimated location of the portable transceiver; further characterised in that the enhanced location anchor transceivers include gas concentration detectors.