A safety sensing system implements a method for a person in an industrial environment comprises providing a personnel locator device (10) for location on a person and a reference system comprising a plurality of nodes (20) located at predetermined locations in the industrial environment (100). Radio ranging signals are transmitted between the nodes (20) and the personnel locator device (10) and measurements of times of flight of the radio ranging signals are derived. The location of the personnel locator device (10) is calculated based on the measurements of the times of flight of the radio ranging signals and reference information representing the predetermined locations of the nodes (10). It is determined if the calculated location of the personnel locator device (10) is within one or more danger zones in the industrial environment (100) and a warning signal is output in response thereto.
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