A system for measuring the position of one or more object in an area of interest, the system comprising: an ultrawideband position measurement system comprising a plurality of beacons (7, 8) which are each located in separate fixed positions with respect to the area of interest; and a tag; and a Global Navigation Satellite System (GNSS); wherein the tag comprises: an ultrawideband receiver which receives UWB data (29,37) for determining the UWB position of the tag with reference to a primary beacon and at least one secondary beacon; a GNSS receiver which receives GNSS data (25, 27) for determining the GNSS position of the tag with reference to GNSS system satellites; a kinematics module which creates kinematic data to determine movement of the tag based upon kinematic changes in the tag a processor which comprises a data augmentation module which calculates position data which represents the most accurate position for the portable tag based upon the UWB position, the GNSS position and the movement of the tag as kinematic sensor information of the kinematics module, characterised in that the tag is a portable tag which is attachable to the object and the data augmentation module comprises an algorithm which: receives GNSS data, UWB position or no data, checks the GNSS data integrity (29,33) and validates the GNSS position for use as the calculated position using UWB position and kinematic sensor information or if the GNSS position is not valid validates the UWB position for use as the calculated position using kinematic sensor information and where no data is received or the UWB position is not valid uses previous valid position data and kinematic sensor data such that the most accurate position of the portable tag is calculated. an ultrawideband position measurement system comprising a plurality of beacons (7, 8) which are each located in separate fixed positions with respect to the area of interest; and a tag; and a plurality of beacons (7, 8) which are each located in separate fixed positions with respect to the area of interest; and a tag; and a Global Navigation Satellite System (GNSS); wherein the tag comprises: an ultrawideband receiver which receives UWB data (29,37) for determining the UWB position of the tag with reference to a primary beacon and at least one secondary beacon; a GNSS receiver which receives GNSS data (25, 27) for determining the GNSS position of the tag with reference to GNSS system satellites; a kinematics module which creates kinematic data to determine movement of the tag based upon kinematic changes in the tag a processor which comprises a data augmentation module which calculates position data which represents the most accurate position for the portable tag based upon the UWB position, the GNSS position and the movement of the tag as kinematic sensor information of the kinematics module, characterised in that the tag is a portable tag which is attachable to the object an ultrawideband receiver which receives UWB data (29,37) for determining the UWB position of the tag with reference to a primary beacon and at least one secondary beacon; a GNSS receiver which receives GNSS data (25, 27) for determining the GNSS position of the tag with reference to GNSS system satellites; a kinematics module which creates kinematic data to determine movement of the tag based upon kinematic changes in the tag a processor which comprises a data augmentation module which calculates position data which represents the most accurate position for the portable tag based upon the UWB position, the GNSS position and the movement of the tag as kinematic sensor information of the kinematics module, characterised in that the tag is a portable tag which is attachable to the object and the data augmentation module comprises an algorithm which: receives GNSS data, UWB position or no data, checks the GNSS data integrity (29,33) and validates the GNSS position for use as the calculated position using UWB position and kinematic sensor information or if the GNSS position is not valid validates the UWB position for use as the calculated position using kinematic sensor information and where no data is received or the UWB position is not valid uses previous valid position data and kinematic sensor data such that the most accurate position of the portable tag is calculated.