PERSONNEL SAFETY SENSING

1 . A safety sensing method for a person in an industrial environment that is a facility in the oil and gas industry, the method comprising:

providing a personnel locator device for location on a person and a reference system comprising a plurality of nodes located at predetermined locations in the industrial environment;

transmitting radio ranging signals between the nodes and the personnel locator device;

deriving measurements of times of flight of the radio ranging signals between the nodes and the personnel locator device;

calculating the location of the personnel locator device within the industrial environment based on the measurements of the times of flight of the radio ranging signals between the nodes and the personnel locator device and reference information representing the predetermined locations of the nodes; and

determining if the calculated location of the personnel locator device is within one or more danger zones in the industrial environment and outputting a warning signal in response thereto.

2 . The safety sensing method according to claim 1 , wherein:

the reference information is communicated to the personnel locator device, and

the step of deriving measurements of the times of flight of the radio ranging signals in respect of respective nodes is performed in the personnel locator device.

3 . The safety sensing method according to claim 2 , wherein the step of determining if the calculated location of the person is within one or more danger zones is performed in the personnel locator device.

4 . The safety sensing method according to claim 3 , wherein the warning signal is communicated from the personnel locator device to the reference system.

5 . The safety sensing method according to claim 1 , wherein the step of determining if the calculated location of the person is within one or more danger zones is performed in the reference system.

6 . The safety sensing method according to claim 5 , wherein the warning signal is communicated from the reference system to the personnel locator device.

7 . The safety sensing method according to claim 4 , wherein the reference system provides an audible or visible alert to a user in response to the warning signal.

8 . The safety sensing method according to claim 4 , wherein the reference system causes operation of equipment within the industrial environment to cease in response to the warning signal.

9 . The safety sensing method according to claim 3 , wherein the personnel locator device provides an audible or visible alert in response to the warning signal.

10 . The safety sensing method according to claim 1 , wherein the reference information is communicated to the personnel locator device as part of the radio ranging signals.

11 . The safety sensing method according to claim 1 , further comprising transmitting zonal information representing the one or more danger zones to the personnel locator device over a radio communication system;

wherein, optionally, the radio communication system over which the zonal information is transmitted to the personnel locator device is separate from the radio ranging signals.

12 . The safety sensing method according to claim 1 , wherein a danger zone is associated with a piece of equipment located in the industrial environment; and

the safety sensing method optionally further comprises:

providing an equipment locator device for location on the piece of equipment;

transmitting radio ranging signals between the nodes and the equipment locator device;

deriving measurements of times of flight of the radio ranging signals between the nodes and the equipment locator device; and

calculating the location of the equipment locator device within the industrial environment based on the measurements of the times of flight of the radio ranging signals between the nodes and the equipment locator device and the reference information, and

wherein the danger zone associated with the piece of equipment is defined with respect to the calculated location of the equipment locator device; and

the safety sensing method further comprises, before calculating the location of the equipment locator device, transmitting zonal information representing the shape of the danger zone associated with the piece of equipment to the personnel locator device over a radio communication system, and

after calculating the location of the equipment locator device, transmitting the calculated location of the equipment locator device to the personnel locator device over the radio communication system.

13 . The safety sensing method according to claim 1 , wherein a danger zone is associated with a piece of equipment located in the industrial environment and the method further comprises receiving control information associated with the piece of equipment, and the danger zone associated with the piece of equipment is dependent on the control information associated with the piece of equipment.

14 . The safety sensing method according to claim 1 , further comprising:

providing an equipment locator device for location on the piece of equipment;

transmitting radio ranging signals between the equipment locator device and the personnel locator device;

deriving measurements of times of flight of the radio ranging signals between the equipment locator device and the personnel locator device; and

determining if the personnel locator device is located within a danger zone defined with respect to the location of equipment locator device based on the measurements of times of flight of the radio ranging signals between the equipment locator device and the personnel locator device.

15 . The safety sensing method according to claim 1 , wherein:

the step of transmitting radio ranging signals between the nodes and the personnel locator device comprises transmitting outbound signals from the personnel locator device to the nodes and transmitting return signals from the nodes to the personnel locator device in response to the outbound signal; and

the derived measurements are measurements of the total time of flight of the outbound signal and the return signal.

16 . The safety sensing method according to claim 1 , wherein:

the step of transmitting radio ranging signals between the nodes and the personnel locator device comprises transmitting an inbound signals from the nodes to the personnel locator device; and

the derived measurements are measurements of the times of flight of the inbound signals.

17 . The safety sensing method according to claim 1 , wherein the radio ranging signals are ultra-wideband signals; and/or

wherein the radio ranging signals are transmitted from different devices and nodes in time slots allocated to respective devices and nodes; and/or

wherein the step of calculating the location of the personnel locator device within the industrial environment comprises calculating the location that minimises an error between the measurements of times of flight; and/or

wherein the personnel locator device comprises an inertial measurement unit and the step of calculating the location of the personnel locator device within the industrial environment takes account of the output of the inertial measurement unit; and/or

wherein the nodes are arranged to detect the angle of arrival of the radio ranging signals, and

the step of calculating the location of the personnel locator device within the industrial environment takes account of the detected angle.

18 . The safety sensing method according to claim 1 , wherein the method further comprises determining if the calculated location of personnel locator device falls within one or more safe zones within the industrial environment represented by the zonal information and ceasing performance of the method in response thereto.

19 . A safety sensing system for a person in an industrial environment that is a facility in the oil and gas industry, the system comprising a personnel locator device for location on a person and a plurality of nodes located at predetermined locations in the industrial environment, the system being arranged to:

transmit radio ranging signals between the nodes and the personnel locator device;

derive measurements of times of flight of the radio ranging signals;

calculate the location of the personnel locator device within the industrial environment based on the measurements of the times of flight of the radio ranging signals and reference information representing the predetermined locations of the nodes; and

determine if the calculated location of personnel locator device falls within one or more danger zones in the industrial environment represented by zonal information and output a warning signal in response thereto.

20 . A personnel locator device for use in a safety sensing system comprising a plurality of nodes located at predetermined locations in an industrial environment that is a facility in the oil and gas industry, the personnel locator device being for location on a person and being arranged to:

derive measurements of times of flight of radio ranging signals transmitted between the nodes and the personnel locator device;

calculate the location of the personnel locator device within the industrial environment based on the measurements of the times of flight of the radio ranging signals and reference information representing the predetermined locations of the nodes; and

determine if the calculated location of personnel locator device falls within one or more danger zones in the industrial environment represented by zonal information and output a warning signal in response thereto.