Patent Publication Number: US-11051156-B2

Title: Tracking and accountability device and system

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a tracking and accountability device and system, and particular to a system for communicating between individuals within and beyond a predetermined range, and for aiding in the safety of emergency responders. 
     Description of Related Art 
     A reliable tracking and communication system is essential for collecting and disseminating information at the scene of an emergency and for directing and controlling personnel and resources at the emergency. Additionally, first responders must have a system in place to enable communication among those on the scene to provide efficient and effective services to those in need of help. Currently, first responder departments have communication and accountability guidelines in place to facilitate communication and safety. For example, to provide tracking an inventory of first responders at the scene of an emergency, the accountability officer typically maintains the position and function of first responding individuals. At the scene of a fire, for example, the accountability officer typically collects the firefighter accountability tags from each firefighter about to enter a burning building. The tags are placed on the accountability tag board under the section corresponding with the firefighter&#39;s assigned position. The accountability officer will also record the names of each firefighter on an accountability board. Throughout the duration of the emergency, the accountability officer remains in radio communication with the firefighters, listens to each individual&#39;s position, and records the position of each during ground operations. This requires the firefighters to update their location at least every 5-10 minutes and for the accountability officer to carefully, and without interruption, listen to the radio updates provided by the firefighters. Upon the return of a firefighter to the accountability officer, the firefighter removes his or her tag from the accountability tag board indicating that the individual firefighter is no longer in the building. 
     A problem with this system is that it requires first responders to provide the necessary data, which can be very difficult to provide in many situations. In addition, it can be difficult to obtain positions of each firefighter by listening to voice communications. Further, the accountability officer is not able to detect whether a first responder is in peril without voice communication. 
     Traditional methods to track emergency responders typically rely on inertial navigation system comprising gyroscopes and/or accelerometers. While these types of sensors permit navigation in an isolated environment without any inputs from any other aiding sensors, error sources can accumulate over time. The gyroscope measurements drift over time and result in inaccurate measurements. Moreover, the gyroscopes and accelerometers have biases and nonlinearity errors that cause errors in estimations. Additional errors, such as computational errors, can accumulate during mathematical integration. Other systems rely on global positioning systems (GPS), which are typically more accurate over the gyroscope and accelerometer as the GPS does not drift. However, GPS has a slow update rate and can be less accurate in the short term than inertial navigation systems using gyroscopes and accelerometers. Further, once the individual enters the building or if the individual is in urban canyons of tall buildings, or in other challenging environments, physical barriers and interference sources may prevent the GPS signals from reaching the device or satellite. 
     BRIEF SUMMARY OF THE INVENTION 
     The present disclosure provides a communication system having a command unit, a processing unit, and a plurality of personal tracking units. 
     In one configuration, a communication system is provided comprising a command unit coupled to a wireless ad hoc network (WANET), a processing unit coupled to the WANET, a first personal tracking unit having a first mobile transceiver in communication with the wireless ad hoc network WANET, the first personal tracking unit coupled to a first set of user identification data of a first individual and being operative to transmit signals representing the first individual&#39;s location over the WANET to the processing unit, and a second personal tracking unit having a second mobile transceiver, the second personal tracking unit coupled to a second set of user identification data of a second individual and being operative to transmit signals representing the second individual&#39;s location (i) to the processing unit over the WANET if the second personal tracking unit is within a first distance; and (ii) to the first personal tracking unit if the second personal tracking unit is within the first distance to the first personal tracking unit. 
     Also provided is a communication system comprising a command unit coupled to a WANET, a processing unit coupled to the WANET, a first personal tracking unit having a first mobile transceiver in communication with the WANET, the first personal tracking unit coupled to a first set of user identification data of a first individual and being operative to transmit signals representing the first individual&#39;s location over the WANET to the processing unit, and a second personal tracking unit having a second mobile transceiver, the second personal tracking unit coupled to a second set of user identification data of a second individual and being operative to transmit signals representing the second individual&#39;s location (i) to the processing unit over the WANET if the second personal tracking unit is within a first distance; and (ii) to the first personal tracking unit if the second personal tracking unit is within the first distance to the first personal tracking unit, wherein each personal tracking unit further comprises a processor, an ambient temperature sensor for generating ambient temperature data, and a display, wherein the processor couples the ambient temperature data with the location data to generate a heat map of the location of the individual to be displayed on the display. 
     In a further configuration, a communication system is provided comprising a command unit coupled to a WANET, a processing unit coupled to the WANET, a first personal tracking unit having a first mobile transceiver in communication with the WANET, the first personal tracking unit coupled to a first set of user identification data of a first individual and being operative to transmit signals representing the first individual&#39;s location over the WANET to the processing unit, and a second personal tracking unit having a second mobile transceiver, the second personal tracking unit coupled to a second set of user identification data of a second individual and being operative to transmit signals representing the second individual&#39;s location (i) to the processing unit over the WANET if the second personal tracking unit is within a first distance; and (ii) to the first personal tracking unit if the second personal tracking unit is within the first distance to the first personal tracking unit, wherein the processing unit couples a plurality of location data points received from the personal tracking units with a preexisting structure map to generate a map having the locations of each personal tracking unit. 
     In another configuration, a communication system is provided comprising a command unit coupled to a WANET, a processing unit coupled to the WANET, a first personal tracking unit having a first mobile transceiver in communication with the WANET, the first personal tracking unit coupled to a first set of user identification data of a first individual and being operative to transmit signals representing the first individual&#39;s location over the WANET to the processing unit, and a second personal tracking unit having a second mobile transceiver, the second personal tracking unit coupled to a second set of user identification data of a second individual and being operative to transmit signals representing the second individual&#39;s location (i) to the processing unit over the WANET if the second personal tracking unit is within a first distance; and (ii) to the first personal tracking unit if the second personal tracking unit is within the first distance to the first personal tracking unit, wherein the personal tracking unit receives from the processing unit an egress map by a reverse data push of the locations of the individual. 
     In a further configuration, a device for determining the environmental conditions in an enclosed space is provided comprising a housing having a sensor module for collecting a plurality of data points, wherein at least one set of data points is one of an ambient temperature and a concentration of gas inside the enclosed space, and a transmitter coupled to a WANET for sending the plurality of data points to a processing unit over the WANET. 
     In yet another configuration, a method of generating a heat map of a structure is provided comprising the steps of receiving from a plurality of personal tracking unit time-stamped data packets comprising ambient temperature data and location data of a structure; combining the ambient temperature and location data with a map of the structure to provide a heat map; transmitting the heat map to a command unit; and displaying the heat map on a display of the portable computer. 
     The method may further comprise determining whether the temperature of the structure is above a structure heat tolerance; and sending an alert to at least one of a command unit and a personal tracking unit if the temperature is above the structure heat tolerance. 
     In yet another configuration, a method of determining a location of an individual in a building is provided. The method comprises coupling a first personal tracking unit (PTU) having a unique identification number to a first set of user identification data of a first individual stored on a separate device; transmitted the unique identification number of the first PTU and the first set of user identification data of a first individual to a processing unit; performing location measurements by at least one of an IMU and a radio location sensor located in the first PTU; transmitting the location measures to the processing unit; determining a location estimate of the first individual based on the location measurements received by the processing unit; accessing a Earth&#39;s Magnetic Field (EMF) map; selecting a portion of an Earth&#39;s Magnetic Field (EMF) map based on the location estimate; performing EMF measurements by a positioning device located in the first PTU; comparing the EMF measurements to the selected portion of the EMF map; and determining the location of the individual. 
     The method may further include the step of displaying the determined location of the individual on at least one of a portable computer and a display on the first PTU. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
       The foregoing features of this invention, as well as the invention itself, may be more fully understood from the following description of the drawings in which: 
         FIG. 1  is a schematic representation of the present system. 
         FIG. 2  is a schematic representation of the Wi-Fi communication network and the ad hoc communication network. 
         FIG. 3A  is a schematic representation of the Command Unit, the Processing Unit and the Personal Tracking Unit (PTU). 
         FIG. 3B  is a schematic representation of an alternative configuration of the Command Unit, the Processing Unit and the Personal Tracking Unit (PTU). 
         FIG. 4  is a block diagram of the process for providing the estimated acceleration, velocity and altitude based on data from the IMU and the additional sensors. 
         FIG. 5  is a flow chart disclosing the method steps of a configuration of the heat map display and alert system. 
         FIG. 6  is a flow chart disclosing the method steps of a configuration of the heat map generation system. 
         FIG. 7  is a flow chart disclosing the method steps of a configuration of zone identification areas. 
         FIG. 8  is a flow chart showing the method steps of a configuration of the coupling of the Personal ID user data with the PTU. 
         FIG. 9  is a flow chart disclosing the method steps of a configuration of the egress map system. 
         FIG. 10  is a schematic representation of the device for determining the environmental conditions in an enclosed space. 
         FIG. 11  is a flow chart disclosing the method steps of a configuration of the step detection and motion characteristics process. 
         FIG. 12  is a flow chart disclosing the method steps of a configuration of the hyperbolic navigation process. 
         FIG. 13  is a schematic representation of an alternative configuration of the present system. 
         FIG. 14  is a flow chart disclosing the method steps of a configuration of location determination of an individual. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     At the outset, it should be appreciated that like drawing numbers on different drawing views identify identical structural elements of the invention. While the present invention is described with respect to what is presently considered to be the preferred embodiment, it is understood that the invention is not limited to the disclosed embodiment. 
     Furthermore, it is understood that the invention is not limited to the particular methodology, materials, and modifications described and as such may vary. It is also understood that the terminology used herein is for the purpose of describing particular elements only, and is not intended to limit the scope of the present invention, which is limited only by the appended claims. 
     A tracking and accountability device and system are disclosed. The device and system tracks the location of individuals in real-time, including, but not limited to, first responders at the scene of an emergency. The system also provides a multi-media situational data pass, including but not limited to a temperature visual overlay or heatmap, which may be displayed in three dimensions. In addition, the system provides an egress map for individuals attempting to exit a dangerous environment. 
     Referring to  FIGS. 1-3  the present system  10  includes a command unit  50 , a processing unit  100 , personal tracking units (PTUs)  150 , and personal identification devices  300 . 
     The command unit  50  includes a portable computer  52 , for example a tablet, laptop, or similar portable computing device, in communication over wireless networks with the processing unit  100  and the PTUs  150 . It is contemplated that there are two wireless communication networks, such as the standard Wi-Fi wireless communication network  58  between the processing unit  100  and the command unit  50  and an ad hoc network  140  between the PTUs  150 , the processing unit  100 , and the command unit  50 . In one configuration, the command unit  50  is arranged to communicate with the processing unit  100  through two distinct methods of communication. First, the command unit  50  may communicate with the processing unit  100  via a standard Wi-Fi wireless communication network  58 . Functional performance data may be transmitted between the processing unit  100  and the portable computer  52  over this Wi-Fi wireless communication network  58 . The wireless communication network  58  is preferably a secure network. Secondly, the command processing unit  100  and  50  may each include a radio location sensor  56 ,  112 , respectively, utilizing ultra-wideband wireless technologies that form an ad hoc network (WANET) as a wireless communication network  140  as described in more detail below. Location data may be transmitted over the wireless communication network  140  between the PTUs, processing unit  100 , and command unit  50 . 
     The portable computer  52  includes a computer program configured to provide the functional performance data and location data transmitted to the processing unit  100  by the PTUs  150  and processed by the processing unit  100  to an individual using the portable computer  52  through a graphical user interface (GUI). The command unit  50  may also include Global Positioning System (GPS) satellite receiver  60  to determine the location of the portable computer  52 . In a configuration, the portable computer  52  includes the radio location sensor  56  and GPS satellite receiver  60 . In yet another configuration, the individual using the portable computer  52  wears a PTU having the radio location sensor  56  and GPS satellite receiver  60 . 
     In select configurations, the command unit  50  includes a voice unit  54  for communicating by voice, by any variety of commercially available voice enabling technologies that enable communication between individuals located at a spaced distance from each other. A satisfactory voice enabling technology includes, but is not limited to, Wireless Local Area Network (WLAN) and Voice over Internet Protocol (VOIP). Alternatively, or additionally, a radio can be used for communicating between individuals. A satisfactory radio includes the Vertex Standard VX-450 Series Portable Radio sold by Vertex Standard LMR, Inc. 
     The processing unit  100  is a server having a mother board coupled to at least some of the following standard components: memory, chipset, processor, standard hard drive controller, expansion slots, I/O ports, and network adaptor. The processing unit  100  further includes a power supply, as described below. The processing unit  100  may store the data received from the PTUs  150  and portable computer  52  in memory  136 . In a configuration, this data may also, or alternatively, be stored on the cloud via remote servers  400  and utilized for training  500 . Typically, the processing unit  100  will connect with the remote servers  400  over an internet connection made when the processing unit  100  returns to the storage facility, for example, a fire engine vehicle returning to its fire station. The processing unit  100  may connect to the servers  400  through a wired connection, wireless connection, or hybrid wired-wireless connection. The stored data may be converted into a form that is acceptable for use by regulatory agencies, such as NFPA, OSHA, DHS, and/or FEMA. The processing unit  100  comprises a radio location sensor  112 , such as the DecaWave ScenSor DW1000 chip described in more detail below for communication between the portable computer  52  and the PTUs  150  over the WANET  140 . 
     The processing unit  100  further comprises a processor  104 . The system  10  can potentially utilize any number of commercially available processors, however, the onboard processor must be fast enough to calculate the algorithms described herein in real-time. Preferably, a multi core processor is used. One example of a multicore processor that may be used is the Quad Core™ Intel® Atom™ Platform sold by Intel Corporation of Santa Clara, Calif. In one configuration, the processor  104  is arranged to communicate with as many PTU data streams that can pass through a single point PTU between the processor  104  and the remaining PTUs. Current technology provides that the processor  104  communicates with approximately seventy-five (75) PTUs  150 . If additional connections are present between the processing unit  100  and the PTUs  150  then the limit would be increased. For example, if three separate connections were present between the processing unit  100  and the PTUs  150 , the limit under current technology would be 225 PTUs. Persons skilled in the relevant art will be aware that the complexity of the SLAM algorithm will increase exponentially with a system having a greater number of PTUs. Therefore, using a more powerful processor will allow additional PTUs to be used with the system  10 . For example, an Intel® Xeon™ processor may permit up to 500 PTUs to be added to the system  10 . Additionally, if the algorithms of the Processing Unit  100  become more demanding, a GPU can be added to the system to increase computational abilities of the Processing Unit  100 . 
     Notwithstanding the foregoing, the minimum number needed for three-dimensional localization of the PTUs  150  is three (3) PTUs and one (1) processing unit  100 , provided however, that any two (2) of the four (4) PTUs are not in a virtual plane. The position estimates may be more accurate with an increase in the number of PTUs  150 . In the event the number of PTUs  150  required at the scene of an emergency exceeds the processor&#39;s limit of PTUs, the system  10  may require additional processors. Additional processing units would communicate with the command unit  50  in the same manner as the first processing unit  100 . In one configuration, the processing unit  100  is mounted on the first responder vehicle  102 , for example, a firetruck, and is associated with a set of PTUs. The processing unit  100  further includes a GPS satellite receiver  106 . In an alternative configuration, the GPS satellite receiver is worn by an individual utilizing the portable computer  52 . In such a configuration, the processing unit  100  mounted to an emergency vehicle  102  obtains its power supply from such vehicle  102 . The processing unit  100  may alternatively, or in addition, include a battery  108  coupled to an LED indicator light  110 , the battery  108  is capable of being charged by shore power when the first responder vehicle  102  is parked at a station. The processing unit  100  may also be charged via the first responder vehicle battery. As discussed below, an indicator  116 , such as an LED indicator light indicates whether the processing unit  100  is in communication with a PTU device  150  and/or the command unit  50  over the wireless communication network  58  and/or the wireless communication network  140 . 
     Turning now to the Personal Tracking Unit (PTU)  150 , each PTU  150  includes a power management system  152  measuring the remaining charge of a battery  154 . An indicator  156 , such as an LED indicator light, may be coupled to the battery  154  to indicate when power is available to the PTU  150 , when power is low, and/or a particular level of the battery charge. The LED indicator light  156  may be a first color, for example, green, when the battery is fully charged, and change to a second color, for example, orange, when the battery is low. The batteries  154  of the PTUs  150  can be charged simultaneously using a bank charger known in the art (not shown) on the first responder vehicle  102 . In one configuration, the bank charger is a 120V charger capable of charging at least six (6) PTUs  150  located and wired directly into the cab of a first responder vehicle  102  and supported by shore power. The PTUs  150  can therefore, be charged in a temperature controlled environment simultaneously with other elements on the first responder vehicle  102 . The bank charger may also comprise the first responder vehicle identifying information  130  and the primary source of the wireless communication network  58 . 
     In one configuration, the wireless communication network  140  includes a radio location sensor  158  coupled to the PTUs, a radio location sensor  112  coupled to the processing unit  100 , and a radio location sensor  56  coupled to portable computer  52 . This wireless communication network  140 , in one configuration, is a wireless ad hoc network (WANET). Each radio location sensor participates in routing by forwarding data from the other radio location sensors. Thus, there is a dynamic determination of which radio location sensor will forward data to the next radio location sensor based on network connectivity. The wireless communication network  140  may operate under separate frequencies for communicating with the PTUs  150  and for communicating with the portable computer  52 . In one configuration, under normal operating conditions, the WANET  140  utilizes 5 Hz-10 GHz broadcasting on every frequency in this range, simultaneously. Preferably, the WANET provides PTU mobility and low overhead of both channel bandwidth and battery power of the PTUs for communicating and processing. A well-known Ad Hoc On Demand multiple path distance vector (AOMDV) may be used to provide reactive routing for the WANET  140 . 
     In one configuration, the radio location sensors  56 ,  112 ,  158  are ScenSor DW1000 chips, which use an IEE802.15.4-2011 UWB compliant wireless transceiver module to communicate and are commercially available from decaWave located at Adelaide Chambers, Peter Street, Dublin  8 , Ireland. The DW1000 chips utilize ultra-wideband wireless techniques which helps reduce the effect of multipath propagation. The DW1000 chip can be used for radio communication as well. In one configuration, this wireless communication network  140  using the DW1000 chip can communicate at a range of up to 300 meters and transfer data at approximately 6.8 Mbps data rate. 
     The network  140  uses an ultra-wideband wireless communication technique based in the IEEE802.15.4-2011 standard and gives the system  10  immunity against multipath fading. The DW1000 chip dimensions are small, 6 mm×6 mm, and requires a very low amount of power: only 31 mA during transmission and 64 mA during reception. The DW1000 chips operate in a network and as a result, if communication between a PTU  150  and the processing unit  100  fails because the PTU  150  is out of range, then the communications are relayed to another PTU in the vicinity of the first responder vehicle  102  having a processing unit  100  and PTU  150 , and that PTU will communicate with the processing unit  100 . It is contemplated that the portable computer  52  will display to the portable computer user, such as the accountability officer, the distances between each PTU  150 , with an accuracy this is approximately within one (1) foot. Moreover, the portable computer  52  will display and identify the individual closest to another individual wearing a PTU, considering the x, y, and z-axis, using appropriate entrances, exits, and stairs, and without permeating floors. 
     The PTU  150  further includes a GPS satellite receiver  160 . The GPS satellite receiver  160  can be used to receive position and velocity with the GPS in most all weather conditions and in most all places on or near Earth. A GPS satellite receiver that may be used with the processing unit  100  as GPS satellite receiver  106  and with the command unit as GPS satellite receiver  60  is a commercially available GPS system from Telit located at 90 High Holborn, London WC1V 6XX, UK. When an individual is outside of a structure, the position may be determined by the GPS satellite receiver  60 ,  106 ,  160  including the initial position of the individual. Global Navigation Satellite Systems (GNSS) may not always be available or reliable. In these situations, data from other sensors of the PTU  150  can be fused to provide positioning information that is refined even when the GPS is unavailable, as described in more detail below. 
     In a configuration, the PTU  150  comprises a digital signal processor  180 . One example of a digital signal processor  180  that may be used is the OMAP L-138 DSP processor commercially available from Texas Instruments, located at 12500 TI Boulevard, Dallas, Tex. 75243. The digital signal processor  180  of each PTU is responsible for processing the data collected by such PTU. For example, the digital signal processor  180  may process the data collected by the PTU with the well-known inertial navigation algorithm, posture detection algorithm, and step detection algorithm, among others, as discussed in more detail below. 
     The PTU  150  further comprises an inertial measurement unit (IMU)  162  providing an inertial navigation system for determining the relative position, velocity and/or altitude of the individual wearing the PTU  150 . The IMU  162  may include an accelerometer (linear motion sensor)  164 , gyroscope (angular velocity sensor)  166 , a pressure sensor (height estimator)  168 , and a magnetometer  169 . In another configuration, the IMU  162  is a Microelectromechanical Systems (MEMS) sensor  170 , which is an accelerometer, gyroscope, and pressure sensor. In one configuration, the PTU  150  includes an IMU  162  having three orthogonal rate gyroscopes and three orthogonal accelerometers. The accelerometer  164  or the accelerometer of the MEMS sensor  170  measures the linear acceleration of the PTU  150  in the inertial reference frame (a fictitious or virtual frame of reference), but in directions that can only be measured relative to the moving PTU  150 . The gyroscope  166  or gyroscope of the MEMS sensor  170  provides angular rates, which can be integrated to determine the orientation of the PTU  150 . The orientation of an individual wearing the PTU  150  can be determined by a sudden change in velocity of the individual as detected by the gyroscope  166  or the gyroscope of the MEMS sensor  170 , which could indicate the individual has fallen or struck the ground very hard. 
     The measurements from the accelerometer  164  and gyroscope  166  or MEMS sensor  170  allow the system  10  to determine the position and orientation of the PTU  150  and therefore the position of the individual relative to their initial position obtained from the GPS  160 . The data from the IMU  162  is processed by the digital signal processor  180  wherein certain algorithms  182  are applied to the data collected by the IMU  162 . For example, the data from the accelerometer  164  and gyroscope  166 , or from the MEMS sensor  170 , of the PTU  150  is applied to the inertial navigation algorithm by the digital signal processor  180  to continuously calculate floor position of the individual via dead reckoning. Thus, the relative position, orientation, and velocity of the moving individual are determined without the need for external references. The position estimate via the PTU  150  is relative to the initial position estimate from the GPS  160  of the PTU  150  or the GPS  106  of the processing unit  106  or the GPS  60  of the command unit  50 . 
     In one configuration, the gyroscope  166  has an accuracy of +/−1 degree and an angle of less than 45 degrees is considered to be horizontal and above 45 degrees is considered to be vertical. The default floor height is typically 10 feet, however, this can be adjusted by the OIC using the computer program on the portable computer  52 . The angular rates measured by the gyroscope  166  or the gyroscope of the MEMS sensor  170  may also serve as the basis of the step detection algorithm, which may be used to correct the drift of the inertial navigation system. The pressure sensors  168  measure atmospheric pressure, which may be used to predict the altitude of the firefighter from the ground level and may aid the inertial navigation system to correct the drift in the navigation algorithm. 
     The accelerometer  164  and gyroscope  166  or MEMS sensor  170  data, however, do not allow accurate autonomous location without external updates, for example from GPS signals, since the sensor signals  164 ,  166  or  170  are affected by various noises and drifts. Since the position and velocity of the individual are updated based on calculations using the initial position and orientation either initialized by another sensor, such as the GPS satellite receiver  160 , or entered by a human operator, the starting position is extremely important since all future estimates of position will be calculated relative to the initial position. To compensate for any errors that may result, external aid, via sensor fusion, is integrated into the inertial navigation system, as discussed below. 
       FIG. 4  is a block diagram showing that data from the IMU  162 , for example from the accelerometer  164 , gyroscope  166 , or alternatively, from the MEMS sensor  170 , is processed by digital signal processor  180  with numerical integrations  208 ,  210 . The resulting position, velocity and altitude determinations may be fed to a statistical filter  204 , such as the Extended Kalman filter or the Particle filter. In some configurations, the well-known inertial navigation algorithm and other well-known algorithms, such as the magnetic heading estimation of the first responder are applied. As shown in  FIG. 4 , data from the additional sensors  202  is processed by the processor  180  to provide at least some of a relative position, velocity and heading, range between neighboring PTUs, altitude, and temperature, which is fed to the statistical filter  204 . The input from the IMU  162  and the additional sensors  202  may also be processed by the processor  180  using the well-known pedestrian navigational algorithms  216  to provide at least the extracted motion characteristics and the step detection, which are fed into statistical filters  204 . The additional sensors  202  may include, for example, any of the following: the radio location sensor (DW1000)  158 , pressure sensor  168 , magnetometer  169 , and temperature sensor  172 . However, it should be appreciated that other sensors may also or alternatively be used. These complex navigational algorithm calculations provide information that is useful and accurate, even if one or more of the sensors are noisy, has a slow update rate, or even when the data has stopped coming from the sensor altogether. In this manner, a filtered position, velocity and altitude provide an estimate  206  of the acceleration, angular velocity, and magnetic heading of the individual wearing the PTU  150 , which is generally drift free, without the need for GPS when the individual (and PTU  150 ) is inside a structure. 
     The DW1000 chip provides relative positioning of the PTUs  150  by enabling calculations of the mutual range of four or more chips. Thus, to provide 3D localization, at least three (3) PTUs and one (1) processing unit  100  will need to be utilized at the scene. Each DW1000 chip of a PTU within a network will know its own position relative to each DW1000 chip of its related PTU. Where there are no obstructions between DW1000 chips, the accuracy in an indoor environment is approximately 10 cm. Accuracy may decrease for Non Line Of Sight (NLOS) cases, however, this will depend on the materials and thickness of the wall blocking the signal. The radio location sensors  112 ,  158  are an aid to the inertial navigation system. Thus, the digital signal processor  180  will avoid using the DW1000 data if there is any sudden change in range estimation from the DW1000 sensors indicating that there is a sudden obstruction prohibiting correct range estimation. To localize a first responder with range measurements from the radio location sensor  112 , hyperbolic navigation using the well-known hyperbolic navigation algorithms may be used. Hyperbolic navigation is provided by measuring the time difference of arrival (TDOA) of two signals from two PTUs. As set forth in  FIG. 12 , each radiolocation sensor  158  embedded on the PTUs will determine the range from itself to the surrounding PTUs within range according to step  1002 . Then, each pair of measurements will form a hyperbolic line according to step  1004 . As set forth in step  1006 , a position fix will be calculated for the PTU using multiple measurements forming hyperbolic lines. According to step  1008 , the process is applied to all the radiolocation sensors within a mesh network, in order to calculate the relative position fix for each. 
     The data from the IMU  162  may also be used to detect the posture of the individual. By posture, it is meant that it can be determined whether the individual is in a vertical or horizontal position, or falling. Posture detection can be determined by the digital signal processor  180  of the PTU  150  receiving the data from the accelerometer  164  and gyroscope  166  or MEMS sensor  170  and applying the well-known step detection algorithm and/or the posture detection algorithm. These computations may also be used to correct the drift in the inertial navigation system. 
     The posture of an individual wearing the PTU  150  may also be determined using motion detection. The processed data from the IMU  162  cannot allow accurate autonomous location without external updates, for example from GPS signals, since their signals are affected by various noises and drifts. Thus, frequent GNSS updates can be used when available. When GNSS aiding is not available, other approaches may be used. For instance, the well-known Pedestrian Dead Reckoning (PDR) using embedded inertial sensors may be used. The accelerometer  164  or MEMS sensor  170  detects the number of steps, determines the step length, and transmits such data to the digital signal processor  180 , wherein the PDR algorithm is applied and the travelled distance is computed. Given a known initial position, the PDR algorithm determines the individual&#39;s position by estimating the heading and the individual&#39;s travelled distance or the individual&#39;s speed. The digital signal processor  180  may also apply well known pattern recognition algorithms, such as neural network, to detect the posture of an individual wearing a PTU  150  as well as the individual&#39;s footsteps. As shown in  FIG. 11 , the pattern recognition algorithm may be applied. First, data is received from the accelerometer  164  and gyroscope  166  or MEMS sensor  170  according to step  902 . In a configuration, data from the magnetometer  169  and pressure sensor  168  may also be used according to step  902 . The pattern recognition algorithm is applied to such data according to step number  904 . As set forth in step  906 , pattern recognition algorithm output analysis is compared to expected human motion data  910  according to step  908 , resulting in step detection and motion characteristics results according to step  912 . 
     In yet another configuration, the processing unit  100  may include a Simultaneous Localization And Mapping (SLAM) unit  118  for determining the position and orientation of the individual. SLAM is a well-known computational process of constructing or updating a map of an unknown environment while simultaneously keeping track of an individual&#39;s location within it. As the individual proceeds into a structure, for example, the PTU  150  will collect the data from the accelerometers and gyroscopes or MEMS sensor  170  as well as other available sensors and transmit metadata to the SLAM unit  118  of the processing unit  100 , including but not limited to any of the following: the position and orientation of the first responder, whether the first responder is standing or falling straight, the ambient temperature, body temperature, carbon dioxide level, carbon monoxide level, humidity, pressure, and flashover detection. The SLAM unit  118  will build a map of the surrounding environment. This map can be used in many cases, such as rescuing trapped firefighter, planning out a safe path through the debris, among others. The map is communicated to the portable computer  52  via the wireless communication network  58 . 
     As shown in  FIG. 3 , the PTU  150  may further include additional sensors  172  that measure biometric data from the individual as well as ambient data. For example, the sensors may measure the blood pressure, pulse, heart rate, oxygen levels, carbon dioxide levels, and body temperature of an individual. Additionally, sensors may measure ambient conditions, including but not limited to, ambient temperature, humidity, concentration of cases such as carbon dioxide levels, carbon monoxide levels, hydrogen cyanide levels, phosgene levels, and oxygen levels, and ambient pressure. This data collected by the sensors  172  will be sent to the processing unit  100  (either directly if the PTU  150  is within a predetermined distance of the processing unit  100  or via another PTU within the predetermined distance of the processing unit  100 ) in the form of data packets. The data packets are time stamped and processed by the processor  104  of the processing unit  100 . In one configuration, the ambient temperate data representing the temperature inside the structure in each area where a firefighter is present will be represented as a heat map overlay by the computer program available on the portable computer  52 . The heat map illustrates the temperatures at various points throughout the building based on temperature data received from each PTU  150  in relation to the time. The heat map may be displayed as color changes and shading over a map display of the internal structure of the building. The heat map may also indicate the stability of certain areas of a building. The colors may be displayed with the temperature measurements in degrees Fahrenheit or Celsius pinned inside the image or within a legend. The heat map may also display other ambient information including, but not limited to gas levels, pressure and humidity. 
     As shown in  FIG. 5 , the heat map  510  may be generated according to the following steps. First, each PTU  150  sends data packets  502  that are time-stamped  504  to the processing unit  100 . As shown in  FIG. 5 , the processing unit  100  may provide the time-stamp  504  for the data packet  502 . However, it should be appreciated by those having ordinary skill in the art that the time-stamp may be provided by the PTU  150  itself. The processing unit  100  will couple the ambient temperature and location data from the PTUs with a map of the structure to provide the heat map. In a configuration of the invention, the heat map  510  is generated as the output of the SLAM algorithm. The processing unit  100  will then transmit the heat map  510  to the portable computer  52  over the wireless communication network  58  wherein the map will be displayed on a GUI. In a configuration, the processing unit  100  also transmits the heat map  510  to the PTU  150 . In a configuration, the heat map includes a preexisting map  506  that is pre-loaded into the system  10 . In another configuration, a pre-loaded map is not used and the heat map is generated based on the location data received from the PTUs  150 . 
     The processing unit  100  will compare the ambient temperature data to a set of structure heat tolerance data  508 . If the ambient temperature is above the structure heat tolerance, the processing unit  100  will send an alert  512  to the portable computer  52  and/or the PTUs. The processing unit  100  will time stamp  514  the alert  512  and in a configuration, send the alert to the PTU  150  and/or the portable computer  52 . The processing unit  100  may also determine if rapid changes in temperature are occurring. In the event of a fire, the processing unit will report whether the fires is at a growth stage, fully-developed stage, or declining state. The processing unit  100  may also indicate the occurrence of a flashover or backdraft. In the event the processing unit  100  determines a potential collapse of the structure based on temperature and time data, the processing unit  100  will send a collapse alert to the portable computer and/or any PTU within a predetermined range of the structure at risk of collapsing. In the event the building materials are known, the stability may be calculated based on the heat tolerances of such materials. For example, in 2014 there were 1.3 million fires in the U.S. and 74% were in residential family homes. The majority of these can be assumed to be wood truss construction, and thus, more than half of the fires in the US are in wood truss homes. A fire directly to the trusses (an attic fire) would collapse in approximately ten (10) minutes. If the fire started on the first floor of a wood truss home, it would take approximately 1-2 hours for the entire house to burn. Other burn time examples based on building construction can be found on the world wide web at https://dps.mn.gov/divisions/sfm/programs-services/Documents/Sprinkler %20Applications/ConstructionTypeDefinitions.pdf and at http://www.fireengineering.com/articles/print/volume-161/issue-5/departments/training-notebook/structural-collapse-under-fire-conditions.html. 
     As shown in  FIG. 6 , the heat map  510  may be generated according to the following steps. First, a plurality of PTUs  150  obtain ambient temperature and location data  516 . The PTUs  150  form data packets containing the ambient temperature and location data and provide a time-stamp  518 . The data packets are transmitted to the processing unit  100  according to step  520  and then the processing unit  100  combines the ambient temperature data with the location data according to step  522 . The processing unit  100  applies the SLAM algorithm according to step  524 . The processing unit  100  generates a heat map according to step  526  which is then transmitted to portable computer  52  according to step  528 . The heat map is displayed on the portable computer  52  according to step  530 . 
     It should be appreciated that the processing of the ambient temperature and location data to generate a heat map may alternatively, or additionally be handled by each PTU processor  180  and this modification is intended to be included herein. 
     In one configuration, the ambient temperature sensor  172  of each PTU  150  measures the ambient temperature every 1/20 th  of a second and measures a range up to 1200 degrees Fahrenheit within an accuracy of +/−5 degrees. Rapid temperature changes are also identified and may be reported to the user of the portable computer  52  as an alert. The heat map, or the temperature data used to build the heat map, may be transmitted from the processing unit  100  to the PTUs to communicate to the individuals wearing the PTUs the temperature of the surrounding area of the individual and/or the stability of the structure surrounding the individual. Alternatively, or additionally, ambient temperature data may be communicated between PTUs, thereby alerting a second individual of high temperatures or potential structural collapse based on the PTU data from the first individual. In cases of fire, the firefighters are typically in fire protective gear that is rated to a predetermined temperature. For example, in full gear, the fire protective gear may protect an individual at a maximum temperature of 500 degrees Fahrenheit for 5 minutes. Thus, in one configuration the user of the portable computer  52  may be alerted if an individual is exposed to the maximum temperature for longer periods and/or at hotter temperatures. 
     It should be appreciated by those having ordinary skill that the PTU  150  may take many shapes and forms. For example, the PTU  150  may include a wrist-mounted device that shows relevant information, such as temperature data, structural stability, the individual&#39;s biometrics and/or an egress map as discussed in more detail below. It is contemplated that alerts that are sent by the processing unit  100  to the user of the portable computer  52  are time stamped and recorded in memory  136  along with the corrective action taken. This data can be analyzed later for training  500 . 
     The following steps may be followed when the system is in use for responding to a fire. First, a first responder vehicle  102 , for example a fire truck, is unplugged from the shore power connection, which activates the locator device on processing unit  100  positioned on the first responder vehicle. The processing unit  100  is automatically recognized by the wireless communication network  58 . The drivers of the first responder vehicles will place the first responder vehicles around the scene of the emergency based on the location of the incident and the function of the first responder vehicle. Each first responder vehicle may have a processing unit  102  that reports the vehicle&#39;s position to the command unit  50 , which can be accessed by user of the portable computer  52 , for example, the Officer in Charge (OIC) or other personnel. In one configuration, the processing unit  100  is included in the bank charger. 
     Once the first responder vehicle  102  is in position, the OIC or the Accountability Officer will activate the portable computer  52  and log into the computer program coupled to the system  10  via the wireless communication network  58 . The first responders, for example, firefighters, will each acquire a PTU  150 , and, if a voice system  54  is not included with the PTU  150 , a radio for communicating with the Accountability Officer and other firefighters by voice. The PTU  150  is in the neutral (initial) position when at the location of the firetruck  102 . The computer program will display the position of one or more firefighters on the display screen of the portable computer  52  based on the tracking information transmitted by each PTU  150  using the tracking and positioning methods described above. 
     In a configuration, the Accountability Officer or other user of the portable computer  52  may identify various work zones using geofencing and the GUI of the computer program. The user of the portable computer  52 , may, for example, select an area considered to be the danger zone and/or a rehabilitation area. The danger zone, in one configuration, may be a representation of a burning building and a forty (40) foot radius around the building displayed on the GUI and the rehabilitation area may represent where the rehabilitation truck, for example, an ambulance is positioned at the scene of an emergency. Thus, when an individual with a PTU  150  is outside of the danger zone, certain algorithms, including but not limited to the posture and motion detection algorithms may not be processed by the processors  104 ,  180 . An indicator may be provided on the GUI to indicate the zone location of an individual wearing a PTU. For example, an icon representing a particular individual wearing a PTU may change to different colors when in each of the different zones. As shown in  FIG. 7 , the method steps may include, but are not limited to a user of the portable computer  52  first selecting an area on the display representing the danger zone and rehabilitation zone according to steps  700  and  702 . Next, the system  10  will determine if the PTU  150  user is in the danger zone  704 . If the answer is yes, the processors  104 ,  180  will continue to process the algorithms according to step  706 . Further, the GUI may provide a location indicator for that particular PTU  150  user indicating that individual is within the danger zone according to step  708 . For example, a representation of the user on the display of the portable computer  52  may be red. If the answer is no, certain algorithms will not be processed by the processors  104 ,  180  according to step  710 . As set forth in step  712 , the system  10  will determine if the individual is within the rehabilitation zone according to step  712 . If the answer is yes, a location indicator may be provided on the display of the GUI showing the PTU  150  user is in the rehabilitation zone according to step  714 . For example, a representation of the PTU  150  user on the display of the portable computer  52  of the PTU  150  user in the rehabilitation zone may include the color yellow. 
     In one configuration, the PTU  150  slides into a holder that may be worn by the individual. For example, a firefighter may have a clip that is pre-pinned to the firefighter&#39;s jacket, wherein the OIC will receive a notification on the portable computer  52  if the PTU  150  is not properly clipped into the activated position. Each clip includes a stored set of personal identification (PID) user data  300  that is linked to the PTU  150  obtained by the individual through radio frequency signals. Having unique identification values embedded within the PTUs only may be problematic in that the same individual must use the same PTU, or the OIC must track which individual is associated with each PTU. In order to solve this problem, each individual is assigned a set of PID user data  300  that is unique to that individual, which may be stored by a PTU holding device or other type of device that is separate from the PTU and capable of retaining a PID user data  300 . The PID user data  300  is then detected by a PTU  150  only when the PTU is proximate to, coupled to, or connected to, the PTU holding device. As shown in  FIG. 8 , the set of PID user data  300 , which is unique to that particular individual, may be bundled in a data packet  308  having other values, and then transmitted to the processing unit  100  by the PTU  150 . For example, each PTU  150  includes a chipset  200  or similar component providing a unique identification value  304  of the PTU  150 , and this information may be bundled in the same data packet  308  having the PID user data  300 . The data packet  308  may also include other data  306 , which may include, but is not limited to, one or more of the following: biometric data from the sensors, voice, gas measurements at the location, and air supply values from the SCBA device. In one configuration, the data packet  308  is time stamped  310  by the PTU  150  and transmitted to the processing unit  100 . The processing unit  100  unbundles the data packet  308 , separating the data and allocating the data into a database  312 . Thus, the display of the portable computer  52  and/or the display of the PTU  150  may identify the individual associated with the PTU. 
     The PTU  150  will send a signal to the server continuously until the PTU  150  receives a confirmation signal confirming connectivity and successful login. Once the PTU  150  is connected to the system  10 , the PTU  150  will transmit the HD user data  300  to the command unit through the processing unit  100  permitting the OIC to identify the individual, and in some configurations, the linked PTU  150  on the display of the portable computer  52 . In an alternative configuration, the PID user data  300  is a component within the PTU  150 , wherein the HD user data  300  is a near field RFID tag having the individual&#39;s identification embedded within the PTU  150 . The RFID tag sends the user data  300  to the RFID transceiver  132  of the processing unit  100 . 
     As the firefighter moves around the scene of the emergency, the PTU  150  will collect raw data from the various sensors  164 ,  166 ,  168 , or  170  of the IMU  162  and from any additional sensors  172 . The PTU  150  will track movement in all Cartesian directions (x, y, and z). Preferably, the movement of each firefighter is be tracked every 1/20 th  of a second, however, it should be appreciated by those having ordinary skill in the art that a movement may be tracked at smaller or larger intervals. Each PTU  150  can communicate with each other if within a distance of approximately 300 meters and more preferably within a distance of 400 meters. Any PTU  150  within the range of the processing unit  100  will be able to send and receive signals to and from the processing unit  100  over the wireless communication network  140 . Using this method, the PTU  150  may transmit and receive signals to and from the other PTUs and to and from the processing unit  100  either directly or through another PTU, regardless of whether the individual and the PTU is in a structure made of concrete, metal, wood, plastic, or other type of building material. If all PTUs are within range of one another, a plurality of connectivity lines can be created as shown in  FIG. 2 . 
     As with most electronic systems, it is necessary to control the temperature, humidity, and other physical factors that may affect the reliability and accuracy of the processing unit  10  and PTUs  150 . The radio location sensors  56 ,  112 ,  158 , for example, may be temperature dependent as the radio wave based positioning depends of the Time Delay Of Arrival (TDOA) of the electromagnetic signal from the transmitter to receiver. If the transceivers  105 ,  151  are subjected to high temperature, the timing unit  120 ,  176  (the crystal) pulse count will vary resulting in an incorrect time estimation and incorrect positioning. Also, the other sensors such as the IMU sensors  164 ,  166 ,  168 ,  169 , or MEMS sensor  170 , and GPS satellite receiver  60 ,  106 ,  160  are dependent on temperature. The desired operating temperature range may be approximately −40 to 158 degrees Fahrenheit, and more preferably between −20 to 125 degrees Fahrenheit. Their measurements will have error due to temperature, shock and humidity. To remove major noise sources and nonlinearities, and to prevent errors due to these physical conditions, these sensors are calibrated at different physical conditions. 
     Since temperature, humidity and other physical factors affect the reliability and accuracy of the system  10 , one configuration includes a temperature control system  178  as part of the PTU  150  to keep the temperature and humidity within the desired operating range and to protect the electronics from extreme ambient temperatures. The command unit  50  and the processing unit  100  may also include a temperature control system  62 ,  134 , respectively. The ambient temperature measurement determined by the temperature sensor  172  may be used to create the heat map and may also be used to determine the temperature surrounding the circuit board of PTUs  150 . 
     In the event an individual requires help or is in danger, the individual can so indicate by activating a distress call by activating a distress call button within the system  10 . In one configuration, the individual activates a button  186  on the PTU  150  to activate the distress call. The user of the portable computer  52 , upon receiving such call or an automated alarm, will use the computer program on the portable computer  52  to alert other individuals within the structure. The alert may be provided to the user of the portable computer  52  through the computer program with a visual, audible and/or vibrational component. The system  10  may also detect non-movement of an individual, or unusual movements that could indicate the individual has fallen down or subject to an explosion and send an alert to the user of the portable computer  52 . To detect non-movement, data from the PTU  150  may be analyzed by the PTU  150  via the well-known “No Movement Algorithm” and “Beyond Human Limitation Algorithm.” The “No Movement Algorithm” quantifies the time that a PTU  150  has not had any movement. In one configuration, the threshold to define movement is one (1) foot and the rate of movement is less than one and one half (1.5) feet per second. For example, if the individual does not move more than 2 feet in a predetermined amount of time, the processing unit  100  will transmit an alert to the portable computer  52 . In the event the PTU  150  is unable to transmit its position, the processing unit  100  will continuously record the last known position for such individual. Communication between a particular PTU  150  and the processing unit  100  may fail in the event such PTU is not within the range of other PTUs or the processing unit  100 , or none of the PTUs are within the range of the processing unit  100 . During a period of lost signal between a PTU and the processing unit  100 , the PTU  150  will continue to collect data and save it on an internal board memory  188 . Upon re-establishment of communication with the processing unit  100 , either directly or through other PTUs  150 , the data saved on the memory  188  will be transmitted to the processing unit  100 . The data stored locally on memory  188  will be time stamped in the PTU  150 . In a configuration, the time stamp is not universal time, but rather timekeeping in an incremental manner relative to the time when signal was lost. Moments of lost signal that are less than ten (10) seconds will not be indicated on the display of the portable computer  52 . However, in the event signal is lost for ten (10) seconds or more, the portable computer  52  user will be alerted on the portable computer and the last known location of the PTU  150 /individual will be displayed as a red alert. Upon the PTU  150  reconnecting to the WANET  140 , the PTU  150  will transmit to the processing unit  100  the current data and any additional data generated during the signal loss. The display will permit the user of the portable computer  52  to group the individuals together and label the group by their job assignment. 
     The system  10  will also monitor whether an individual has exceeded the limits of human movement and speed by applying the Beyond Human Limitation Algorithm to tracking data transmitted by a PTU  150 . In one configuration, the threshold to define the limitation in the x and y axis is 10 mph and the threshold to define the limitation in the z axis is 3.5 mph. The PTU  150  will measure these speeds and transmit the data to the processing unit  100 . If these speeds are exceeded, the processing unit  100  will send an alert to the portable computer  52  to notify the portable computer  52 . 
     The alert types may be assigned different colors indicating the severity and type of danger. For example, the indicator for non-movement of an individual using a PTU  150  may be yellow in the event no movement is detected for fifteen (15) seconds and proceed to red at twenty (20) seconds. The indicator values may be adjusted within the computer program. 
     The system  10  may provide an egress map to individuals wearing a PTU  150  showing the individual&#39;s measured path in reverse. In one configuration, as shown in  FIG. 9 , the PTU  150  sends an IMU data packet  550  that is time stamped  552  to the processing unit  100 . In another configuration, the processing unit  100  time stamps the data packet  550 . The processing unit  100  stores the data in memory  136 . Through a reverse data push  554 , the processing unit  100  will send to the PTU  150  the reverse tracking information of the individual. It is contemplated that the reverse data push may be automatic or at the request of an individual wearing the PTU  150 . Thus, an individual wearing a PTU  150  in a building or other emergency environment will be guided to the exit based on previous steps. In some configurations, the map of a building subject to the emergency is known prior to the event. Thus, the closest entrances, exits and/or windows can be identified and the individual wearing the PTU  150  can be guided by the PTU  150  to the closest escape via an egress map communicated from the processing unit  100  to the PTU. In one configuration, the egress data is provided to the PTU  150  upon a request  556  by the user of the PTU  150 . Such building maps may be created during new building walkthroughs, building inspections, by the SLAM unit  119 , or otherwise. The egress map may be displayed on a wrist display, on the visor of a first responder, or by other devices worn by the first responder. In a configuration of the invention, a large arrow is displayed providing directional guidance (N, S, E, W). The display may change colors or include a secondary arrow to indicate a change of elevation to the individual. 
     In yet another configuration, as shown in  FIG. 10 , the PTU is a device  600  for determining the environmental conditions in an enclosed space. The device  600  includes a housing  602  having a sensor module  604  for collecting a plurality of data points. In one configuration, the sensor module  604  measures the concentration of gas of carbon dioxide levels, carbon monoxide levels, hydrogen cyanide levels, phosgene levels, oxygen levels, and/or other chemicals. The sensor module  604  may also measure ambient temperature, pressure, vibration, radiation, humidity, and/or other environmental elements. The device  600  further comprises a transceiver  606  coupled to a wireless communication network  140  for sending a plurality of data points to a processing unit  100 . The processing unit includes a processor for comparing the plurality of data points to a set of acceptable data points limits and determining if the plurality of data points is within the acceptable data point limits. If the data points are determined to be outside the acceptable range, the processing unit  100  communicates an alert to one of a command unit  50  and the device  600 . For example, the alarm may sound if the carbon dioxide levels are greater than 1,000 ppm, carbon monoxide levels are greater than 70 ppm, hydrogen cyanide levels are greater than 8 ppm, and/or if the phosgene levels are greater than 2 ppm. 
     Referring now to  FIG. 13 , in an alternative configuration of the present system  800 , the system utilizes the Earth&#39;s magnetic field (EMF) to enable positioning of an individual. The EMF may be utilized independently or in combination with GPS  160 , radio location sensor  158 , and/or IMU  162 . In one configuration, the PTU  150  is as described supra, and includes a positioning device  800 . The positioning device  800  may comprise a magnetometer or another sensor capable of measuring an EMF field. The magnetometer may be, for example, a Hall sensor or a digital compass. In one configuration, the positioning device is a group magnetometer, or a magnetometer array. In another configuration, the positioning device is magnetometer  169 . The positioning device measures an EMF vector. In one configuration, the magnetometer measures a three-dimensional magnetic field vector. The EMF vector measured by the positioning device may be compared to an indoor Earth&#39;s magnetic field map, which comprises existing information, such as EMF vector magnitude and direction in several locations within a building or several buildings. The EMF map may be generated by taking a plurality of EMF measurements at a plurality of locations in one or more building. The EMF measurements may be generated using a mapping device. The EMF measurements may include the magnitude and direction of the Earth&#39;s magnetic field. In one configuration, the mapping device is a mobile device having a magnetometer and/or radio interference components. The positioning device  800  or  169  may have the EMF map stored within the positioning device itself, within the memory  188  of the PTU  150 , or stored elsewhere on a network accessible by the positioning device. Alternatively, the PTU  150  may forward the EMF vector data to the processing unit  100  having the EMF map stored in memory  136  or having access to the EMF map stored in a database or server, for example, cloud storage  400 , accessible through a network. The EMF vector measured by the positioning device is compared to the indoor Earth&#39;s magnetic field map to determine the location of the user in the building. It should be appreciated by those having ordinary skill in the art that the EMF map may include extensive amounts of data. Thus, in one configuration, only a portion of the EMF map is used based on a location estimate measured by the PTU  150 . That is, the IMU  162 , Radio location sensor  158 , and/or GPS  160  may measure the location of an individual and the PTU  150  and/or processing unit  100  may determine a location estimation of the individual. A portion of the EMF map is selected based on this location estimate. Then, the EMF vector measurements are compared to the EMF map portion to determine a location of an individual. 
     As set forth in  FIG. 14 , in one configuration, a method of location determination  802  is shown. In this method  802 , using the PTU  150 , measurements by the IMU  162 , radio location sensor  158 , and/or GPS  160  are performed according to step  804 . Then, a location estimate of the individual having the PTU  150  is determined according to step  806 . In one configuration, the measurements performed by the IMU  162  include measurement data from the accelerometer  164 , gyroscope  166 , or alternatively, from the MEMS sensor  170 , which is processed by digital signal processor  180  with numerical integrations  208 ,  210 . The resulting position, velocity and altitude determinations may be fed to a statistical filter  204 , as described supra. In an alternative configuration, the measurements performed by the IMU  162  are transmitted to the processing unit  100 , where data is processed by processor  104  to determine the location estimate of the individual having the PTU  150 . Data from the additional sensors  202  may also be processed by the processor  180  and/or  104 , and if available, GPS  160 , may also be used to determine the location estimate of the individual having the PTU  150 . This location estimate provides a basis for selecting a portion of the EMF map according to step  808 . The processor  180  of the PTU  150  or the processor  104  of the processing unit  100  selects the relevant portion of the EMF map based on the location estimate. The relevant portion of the EMF map includes the area surrounding the location of the PTU  150 . The relevant portion of the EMF map may include a floor of a building, a portion of a room, a multi-floor section of a building, or any other part of the EMF map relevant to the location of the individual having the PTU  150 . The EMF map may be stored in the memory of the PTU  150  and/or the memory of the processing unit  100 . The EMF measurements may also be performed by the positioning device according to step  810 . As set forth in step  812 , the EMF measurements are compared to the portion of the EMF map selected based on the location estimate. Finally, according to step  814 , the location of the individual having the PTU  150  is determined. 
     In one configuration, a location of an individual having a PTU  150  may be determined, in part, by using Indooratlas® location technology, which can be found at http://www.indooratlas.com. Background information regarding the Indooratlas® technology can be found in the white papers titled “Ambient Magnetic Field-Based Indoor Location Technology” available at http://web.indooratlas.com/web/WhitePaper.pdf, and “Magnetic Positioning: The Arrival of ‘Indoor GPS’ available at https://www.indooratlas.com/wp-content/uploads/2016/03/magneticpositioning opus_jun2014.pdf, the entirety of each article hereby incorporated by reference. 
     The location of the individual may be displayed on a GUI of a portable computer  52  and/or on a GUI of the PTU  150 . The PTU  150  may include, for example, a wrist-mounted device that shows relevant information, such as location information, temperature data, structural stability, the individual&#39;s biometrics and/or an egress map. 
     The present invention contemplates that many changes and modifications may be made. Therefore, while the presently-preferred form of the system has been shown and described, and several modifications and alternatives discussed, persons skilled in the art will readily appreciate that various additional changes and modifications may be made without departing form the scope of the invention, as defined and differentiated by the following claims.