Abstract:
Techniques for navigating a high temperature low visibility environment are supported. A system may employ appropriate sonar signals to determine and display the location or distance to remote structures that may be obscured in the high temperature low visibility environment. Firefighters, military personnel, and other individuals that must navigate through obscured, high temperature environments may interact with suitable devices, such as a handheld device, to access and display the approximate location or distance of the remote structures or pathways. These devices may facilitate effective navigation of high temperature low visibility environments, thereby minimizing the risk of traumatic or fatal bodily injuries posed by the dangerous conditions.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims the benefit of priority of U.S. Provisional Patent Application No. 61/815,472 filed on Apr. 24, 2013. 
     
    
     TECHNICAL FIELD 
       [0002]    The present disclosure relates generally to acoustic sonar imaging systems, and more specifically to acoustic sonar imaging systems for obscured, high temperature environments. 
       BACKGROUND 
       [0003]    Many individuals must navigate through obscured, high temperature environments. For example, fire fighters may need to navigate a fire ground, or military personnel may need to navigate a battlefield. In those situations, active flames, and aerosol particles such as smoke, dust, vapors or other airborne particles can reduce visibility, and thereby limit navigation in those environments in a safe and efficient manner. Specialized equipment may facilitate navigating such obscured, high temperature environments characterized by low visibility and involving high risk of traumatic bodily injury or life. 
       SUMMARY 
       [0004]    In accordance with the present disclosure, a navigation method and system for navigating obscured, high temperature environments characterized by low visibility is provided which substantially eliminates or reduces disadvantages and problems associated with previous systems and methods. 
         [0005]    According to a particular embodiment, a handheld navigation apparatus is provided, which includes a display, a memory for maintaining a sonar processing application, a transmitter capable of transmitting low frequency sonar signals, an array of sensors capable of detecting low frequency sonar signals, and a processor capable of executing the sonar processing application to implement various features. In particular, the sonar processing application can be executed to transmit, using the transmitter, a frequency modulated sonar signal of long duration toward a remote object located in the obscured high temperature environment and receive, using an array of sensors, spatially diverse reflections of the frequency modulated sonar signal. In addition, the sonar processing application can calculate a cross correlation of the received reflections of the frequency modulated sonar signal to the transmitted frequency modulated sonar signal, determine the approximate distance of the remote object located in the obscured high temperature environment based on the calculated cross correlation, and display an image on the display depicting the approximate distance of the remote object. 
         [0006]    Particular embodiments may overcome limitations of existing navigation tools. For example, information gathered by systems and methods of the present disclosure may be resistant to heat and open flames that may significantly degrade thermal imaging camera performance. Thus, some embodiments may enable users to detect remote objects through an actively burning fire. In addition, some embodiments may facilitate differentiating structures that may appear similar on a thermal imaging camera system because they have approximately the same temperature as the background or other co-located structures. Moreover, certain embodiments of the present disclosure may facilitate penetrating the turbulent structure of the fire that may cause distortion in certain types of signals. Thus, the teachings of the present disclosure may be employed to provide visualization in a wider range of obscured, high temperature conditions and facilitate navigation in those dangerous environments by enhancing spatial perception. 
         [0007]    Some embodiments may be used to help firefighters navigate a burning building either as a standalone sonar system or combined with a thermal imaging camera system. Particular embodiments may also use sonar signals to obtain an image of the active fire itself. Thus, a thermal imaging camera system may be complemented with teachings of the present disclosure to enhance a user&#39;s awareness of structures and dangerous elements in a high temperature low visibility environment. Other embodiments may include suitable environmental and/or atmospheric sensors (e.g., thermometers, bolometers, barometers, and/or water vapor sensors) in order to determine the evolution of the obscured, high temperature environment over time. Such embodiments may facilitate higher resolution distance calculations based on adjustments to the speed of sound given varying environmental conditions. Certain embodiments may be employed in mobile platforms, such as mobile search and rescue robots used to assist fire fighters. Particular embodiments may be used by military personnel to visualize and determine distances of remote objects in the field using appropriate sonar signals to characterize environments obscured by fire, smoke, dust, fog, or other particles that may diminish visibility. Particular embodiments may use suitable sensors of position or movement, such as accelerometers and/or gyroscopes, to measure, calculate, store, and display information regarding position, speed, orientation, angle, or other appropriate information. For example, the teachings of the present disclosure may be combined with systems capable of determining positions in a three-dimensional space, angle of orientation, heading, elevation, and bank (e.g., yaw, pitch, and/or roll). Such additional information may enable a suitable system to provide a user with a comprehensive image of an obscured, high temperature environment as it may change over time and in relation to movement of the system or the user. This additional information may also facilitate determining the location of the flame of an active fire with higher resolution, and further determine how the flame changes over time. 
         [0008]    Other embodiments may be employed in mobile platforms, such as mobile search and rescue robots used to assist fire fighters. Particular embodiments may be used by military personnel to visualize and determine distances of remote objects in the field using appropriate sonar signals to characterize environments obscured by fire, smoke, dust, fog, or other particles that may diminish visibility. 
         [0009]    Other embodiments may be employed in a form that can be worn by the user or operate in conjunction with systems used or worn by the user. For example, particular embodiments may be incorporated within or used in conjunction with appropriate headgear, eyewear, or clothing. In some embodiments, appropriate navigation information, including but not limited to information determined according to the teachings of the present disclosure, may be communicated electronically to other systems used or worn by the user such as suitable headgear, eyewear, or clothing, or to remote systems such as a centralized incident command center. 
         [0010]    Other technical advantages of the present disclosure will be readily apparent to one skilled in the art from the following figures, descriptions, and claims. Moreover, while specific advantages have been enumerated above, various embodiments may include all, some, or none of the enumerated advantages. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    Embodiments of the present disclosure may be better understood through reference to the following figures in which: 
           [0012]      FIG. 1  is a block diagram illustrating an example handheld navigation system for navigating a high temperature environment. 
           [0013]      FIG. 2  illustrates an example process flow for determining approximate distance of remote objects in a high temperature environment. 
           [0014]      FIG. 3  is an example high temperature environment for detecting the location of a remote wall in a high temperature environment. 
           [0015]      FIG. 4  is a color plot of example results from using a handheld navigation system of the present disclosure in a high temperature environment with a seven kilowatt fire in a room with a remote wall. 
           [0016]      FIG. 5  is a color plot of example results from using the handheld navigation system of the present disclosure in a high temperature environment with a forty-three kilowatt fire in a room with a remote wall. 
           [0017]      FIG. 6  is an example high temperature environment for detecting the location of a remote doorway in a high temperature environment. 
           [0018]      FIG. 7  is a color plot of example results obtained using the handheld navigation system of the present disclosure in a high temperature environment with a forty-three kilowatt fire in a room with remote walls forming a doorway. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    The present disclosure may be better understood through reference to the following examples. These examples are included to describe exemplary embodiments only and should not be interpreted to encompass the entire breadth of the present disclosure. 
         [0020]      FIG. 1  is a block diagram illustrating an example handheld navigation system for navigating an obscured, high temperature environment. As illustrated, an example embodiment of a handheld navigation system  100  is shown which has elements that interoperate to facilitate navigation in high temperature low visibility environments. The elements of system  100  can provide navigational support to various stakeholders including firefighters, military personnel, and rescue crews. In particular embodiments, system  100  may allow user to determine the distance of a remote object in environments such as a smoke-filled room or a room engulfed with flames, or other high temperature low visibility environments. For example, certain embodiments of system  100  may determine distances to remote objects located within a burning structure, such as a wall or doorway, thereby enabling users of the handheld device to navigate the dangerous environment. In particular implementations, the teachings of the present disclosure may be combined with video cameras, infrared cameras, or other suitable navigation tools to enhance a user&#39;s awareness of the obscured, high temperature environment and safely maneuver the situation. 
         [0021]    As illustrated, handheld navigation system  100  includes a number of components for determining and displaying approximate distance information regarding remote objects or structures. Handheld navigation system  100  may represent any suitable portable hardware, including appropriate controlling logic and data capable of receiving user input, determining an approximate distance to remote object in a low visibility environment and displaying an appropriate image depicting the distance of the remote object. For example, handheld navigation system  100  may be a standalone embedded system or included as an application on larger system providing other additional functionality. In certain implementations, the features and functionality of handheld navigation system  100  may be embodied in a smartphone, such as an APPLE iPHONE or suitable ANDROID smartphone device, or on an appropriate handheld computing device such as a tablet computer. As shown, handheld device  100  includes several components, which may include a transmitter  102 , an array of sensors  104 , a display  106 , a memory  108  and a processor  110 . 
         [0022]    Transmitter  102  represents any combination of hardware and controlling logic for generating sonar signals of low frequency. For example, transmitter  102  may, in certain embodiments, be a speaker for generating low frequency sounds. In certain embodiments, the frequencies transmitted by transmitter  102  may range from approximately one hundred hertz (Hz) to approximately thirty kilohertz (kHz). The transmitter  102  may also be capable of transmitting a low frequency frequency-modulated signal into an obscured, high temperature environment for a long duration that may range between one tenth of a second to half a second. In other embodiments, transmitter  102  may represent a series of transmitters capable of sending multiple low frequency signals. For example, transmitter  102  may be a parametric array transmitter. In particular embodiments, the transmitter is capable of transmitting a linear frequency modulated signal. Thus, transmitter  102  allows the user to transmit suitable low frequency sonar signals into an obscured, high temperature environment for determining the approximate distance of remote objects. 
         [0023]    Array of sensors  104  represents any combination of hardware and controlling logic for detecting reflections of low frequency signals in an obscured, high temperature environment. In certain embodiments, sensors  104  may be a series of microphones. For example, particular implementations may employ a series of shotgun microphones arranged to capture sonar signals arriving from multiple angles. Particular embodiments may use the information gathered by the array of sensors  104  to electronically steer or beamform, such that interference is minimized and resolution of the data calculated by the system is increased. Sensors  104  are capable of converting low frequency sonar signals into digital data for use by other elements of system  100 , such as storage by memory  108  and further processing by processor  110 . In other embodiments, sensors  104  may include a series of microphones of various types for capturing different types of reflections. In particular implementations, the array of sensors  104  are capable of sensing reflections of low frequency sonar signals from remote objects, converting those signals into digital data, and facilitating processing by other elements of system  100 . Although the illustrated system depicts an array of sensors, embodiments of the present disclosure may use a single sensor or any suitable number of sensors, whether disposed in array or at select positions within or around handheld navigation system  100 . 
         [0024]    Display  106  represents any appropriate combination of hardware, control logic and data for displaying information to a user. In certain embodiments, display  106  may also receive input from the user, thus display  106  may include any suitable input and/or output interface. For example, a user interface may be a suitable touch screen interface that is capable of both displaying graphical information and receiving user input. In other embodiments, display  106  only displays information to the user and does not receive input. In those embodiments, input from the user may be provided by other buttons, a keypad, trackball, track pad, touch screen, or other appropriate actuatable switches provided by handheld navigation system  100 . Display  106  may be employed to display an image of the environment that includes the approximate distance information of a remote object calculated by components of handheld navigation system  100 . In other embodiments, display  106  may specify the approximate distance of the remote object in numerical form, plotted on a Cartesian coordinate system, or provided in other suitable form. 
         [0025]    Memory  108  represents appropriate hardware and control logic for maintaining a sonar processing application and digital sonar data corresponding to transmitted sonar signals or reflections of transmitted sonar signals. The sonar processing application may include the appropriate computer instructions to implement some or all of the features of the present disclosure. Memory  108  may also include storage for other data such as an operating system of system  100 . In particular embodiments, memory  108  may include a non-volatile portion and a volatile portion. Non-volatile portion of memory  108  may represent memory for maintaining persistent applications and/or data. The volatile portion of memory  108  represents storage for maintaining non-persistent applications and/or data. Thus, memory  108  may be used to maintain persistent data and non-persistent data corresponding to features of the present disclosure. For example, memory  108  may be employed to store digital representations of the transmitted low frequency sonar signal and/or store digital representations of the reflected low frequency sonar signals. In certain embodiments, memory  108  may be used to store intermediate results of any pertinent calculations performed by processor  110 . 
         [0026]    In particular embodiments, handheld navigation system  100  is capable of transmitting low frequency sonar signals in an obscured, high temperature environment, receiving reflections of those low frequency signals, and determining the approximate distance of a remote object located in the obscured, high temperature environment based on a calculated correlation of the received reflections to the transmitted low frequency sonar signals. In addition, handheld navigation system  100  may display information regarding the approximate distance to the user or the handheld navigation system  100 . For example, handheld navigation system  100  may display the distance of a remote object graphically on a visual image of the obscured, high temperature environment. In other embodiments, handheld navigation system  100  may display a numerical value or plotted value on a Cartesian coordinate system corresponding to the approximate distance of the remote object. In other embodiments, handheld navigation system  100  may display a graphical representation of distance as an overlay upon an infrared or video image of the obscured, high temperature environment. The visual image may be a video image, an infrared image, or other suitable image provided by an appropriate camera. Thus, a handheld device, such as handheld navigation system  100 , enables a user to safely navigate low visibility, high temperature environments efficiently and reduce thereby reduce the likelihood of bodily injury or death in such dangerous environments. 
         [0027]    In operation, elements of handheld navigation system  100  perform various functions including enabling user input, transmitting low frequency sonar signals in an obscured high temperature environment, detecting reflections of those signals, calculating the cross correlation between the reflected signals and the transmitted low frequency signals, and determining the approximate distance of a remote object. The distance determination may be displayed to the user as a graphical image or a value corresponding to the distance of the remote object. Thus, elements of handheld navigation system  100  can increase the likelihood that users are able to safely navigate a fireground or other high temperature low visibility environments efficiently. 
         [0028]    For example, elements of system  100  are operable to determine distances of various objects using low frequency sonar signals. In particular, in response to user input, processor  110  may cause a sonar processing application residing in memory  108  to execute appropriate logic in order to control transmitter  102 . Transmitter  102  may be controlled and instructed to send a low frequency, frequency modulated signal in an obscured, high temperature environment. In particular embodiments, the transmitted signal may be a linear frequency modulated signal. The processor  110  may also execute appropriate instructions of the sonar processing application residing in memory  108  to cause the array of sensors  104  to collect reflections of the transmitted signal from the environment. In response to collecting the reflections of the low frequency, frequency modulated signal, system  100  may store the collected data in memory  108  using processor  110 . Processor  110  of system  100  may then proceed to determine the cross correlation between the reflected signals and the transmitted signals in order to determine when the cross correlation is the highest. Next, applying the appropriate speed of sound for the obscured, high temperature environment, system  100  may cause processor  110  to determine the appropriate distance to the remote object. The speed of sound may vary depending on the temperature of the temperature of the environment. For example, the high temperature of the environment may cause sound signals to travel at a higher speed than at normal room temperature, holding all other factors such as air pressure and humidity constant. Some embodiments may take into account information retrieved from one or more sensors to determine the appropriate speed of sound. For example, appropriate sensors may provide information that may have an effect on the appropriate speed of sound in a given environment, such as temperature, humidity, air pressure, and/or other environmental conditions. In other embodiments, system  100  may use the speed of sound at room temperature under normal conditions or typical conditions for the type of obscured, high temperature environment. Next, handheld navigation system  100  may display the resulting calculated approximate distance using display  106 , either in numerical form or in an appropriate graphical form. For example, in certain embodiments, display  106  may display an infrared image from an infrared camera and the distance information may be presented as an overlay on a video or infrared image. Other embodiments may plot the distance information on a Cartesian coordinate system or other suitable coordinate system. Thus, a user of handheld navigation system  100  may determine distances in real time in order to be able to safely navigate a fireground, a smoky environment or other high temperature, low visibility environments. 
         [0029]    While system  100  is illustrated as including specific components, it should be understood that various embodiments may operate using any suitable arrangement and collection of components. For example, system  100  may be employed as a standalone system, collection of systems, or embodied as an application in a system capable of providing numerous other features. In particular embodiments, a sonar system may be combined with a thermal imaging camera system. Other embodiments may also use sonar signals to obtain an image of the active fire flame. Certain embodiments may include suitable environmental and/or atmospheric sensors (e.g., thermometers, bolometers, barometers, and/or water vapor sensors) in order to determine the evolution of the obscured, high temperature environment over time. Such embodiments may facilitate higher resolution distance calculations based on adjustments to the speed of sound given varying environmental conditions. Other embodiments may be employed in mobile platforms, such as mobile search and rescue robots used to assist fire fighters. Particular embodiments may be used by military personnel to visualize and determine distances of remote objects in the field using appropriate sonar signals to characterize environments obscured by fire, smoke, dust, fog, or other particles that may diminish visibility. 
         [0030]    Particular embodiments may use suitable sensors of position or movement, such as accelerometers and/or gyroscopes, to measure, calculate, store, and display information regarding position, speed, orientation, angle, or other appropriate information. For example, the teachings of the present disclosure may be combined with systems capable of determining positions in a three-dimensional space, angle of orientation, heading, elevation, and bank (e.g., yaw, pitch, and/or roll). Such additional information may enable a suitable system to provide a user with a comprehensive image of the obscured, high temperature environment as it may change over time and in relation to movement of the system or the user. This additional information may also facilitate determining the location of the flame of an active fire with higher resolution, and further determine how the flame changes over time. 
         [0031]    Other embodiments may be employed in a form that can be worn by the user or operate in conjunction with systems used or worn by the user. For example, particular embodiments may be incorporated within or used in conjunction with appropriate headgear, eyewear, or clothing. In some embodiments, appropriate navigation information, including but not limited to information determined according to the teachings of the present disclosure, may be communicated electronically to other systems used or worn by the user such as suitable headgear, eyewear, or clothing, or to remote systems such as a centralized incident command center. 
         [0032]      FIG. 2  is a process flow diagram illustrating a process flow  200  for determining an approximate distance to a remote object in a high temperature, low visibility environment. The steps of process flow  200  correspond to an example sequence of steps for navigating high temperature environments such as structures engulfed with flames, smoky environments, a war zone or other high temperature situations characterized by low visibility, for example, due to aerosol particles (e.g., smoke, dust, sand). Such a process of determining the approximate distance of remote objects enables individuals, such as firefighters or military personnel, to be able to navigate difficult and dangerous circumstances posed by fire, smoke or other high temperature elements or aerosol particles. A process like process flow  200  may be implemented on a handheld navigation system such as system  100 , which provides an interface to the user to provide input and receive output related to the distance calculations ascertained by the system. 
         [0033]    In the illustration, process flow  200  includes a number of steps for transmitting and collecting information about low frequency signals in the obscured, high temperature environment, performing a number of calculations. and determining the approximate distance of remote objects in the area. This information can be displayed in a suitable form at the end of process flow  200 . As illustrated, system  200  begins at step  202  and ends at step  214 . The steps of system  200  include transmission step  204 , reception step  206 , correlation step  208 , distance calculation step  210  and displaying step  212 . This collection of steps may be performed, for example, on a handheld navigation system, such as handheld navigation system  100 , through an appropriate user interface for interacting with the device. 
         [0034]    In operation, process flow  200  begins at step  202 . The first step in the process of process flow  200  is at transmission step  204 . At transmission step  204 , the system transmits a low frequency, long duration, frequency modulated signal towards a remote object in an obscured, high temperature environment. In particular embodiments, the transmitted signal may be a linear frequency modulated signal. In this step, a sonar signal may be transmitted towards areas of interest within an environment, the use of low frequency and long duration signal facilitates the accurate collection of reflections of those signals with little interference due to smoke, flames, or temperature. In obscured, high temperature environments such as those including active fires, the use of long duration low frequency signals eliminates any inaccuracies that may result from the effects an unpredictable flame may have on higher frequency signals. In certain embodiments, using a long duration low frequency signal may average out the effects of a high frequency flame. In particular embodiments, the duration of the low frequency signal may range between one tenth of second and half a second and the frequencies of the transmitted signal may range between one hundred hertz and thirty kilohertz. The signal may be transmitted by an appropriate speaker, such as a tweeter speaker or other suitable low frequency transmitter. In certain embodiments, the low frequency long duration signal is transmitted as a frequency modulated signal spanning a range of appropriate low frequencies. For example, the transmitted signal may be a linear frequency modulated signal. 
         [0035]    Next, the handheld device proceeds to reception step  206  where reflections of the transmitted frequency modulated signal are received on an array of sensors. In particular embodiments, the sensors may be a series of microphones. For example, the sensors may be a series of shotgun microphones capable of collecting reflections from various angles of the room. Process flow  200  then enters cross correlation step  208  where the processor of the handheld navigation system calculates the cross correlation between the reflections received on the array of sensors and the transmitted frequency modulated signal. Using the cross correlation values and the speed of sound corresponding the high temperature environment, the handheld navigation system may perform a distance calculation in distance calculation step  210 . The speed of sound may vary according to the temperature of the obscured, high temperature environment which may be sensed using an appropriate temperature sensor on the handheld navigation device. This information may be used in distance determination step  210  in order to determine a more accurate distance of the remote object of interest. In other embodiments, the speeds of sound at room temperature under normal conditions, or an approximation of the temperature in the environment may be employed to determine the approximate distance of the remote object. In some embodiments, the approximate temperature of the environment may be provided by the user. In other embodiments, more accurate temperature values may be obtained using other sensor systems, such as a thermometer or a radiation sensing bolometer. Finally, in step  212 , an image reflecting the approximate distance to the remote object may be displayed. In particular embodiments, this may involve overlaying the distance information on a previously collected or simultaneously collected video or infrared image of the obscured, high temperature environment. In other embodiments, the distance information may be displayed as a numerical value or other suitable coordinate scale such that the user can determine the relative location of specific structures within the user&#39;s environment. In particular embodiments, process flow  200  enables the user to safely navigate the obscured, high temperature environment efficiently, and thereby minimize bodily injury or death. Process flow  200  ends at step  214 . 
         [0036]    While process flow  200  is illustrated as including specific steps, it should be understood that various embodiments may implement a distance determination scheme for navigating an obscured, high temperature environment using any appropriate combination of steps for providing access to distance information regarding remote objects. For example, process flow  200  may be modified or combined with separate processes provided by other suitable navigation tools, such as video cameras and infrared cameras, to enhance the user&#39;s ability to quickly and safely navigate high temperature low visibility environments. As another example, process flow  200  may be modified to receive acoustic signals generated by an alarm device located in the high temperature environment or worn by an individual or robot in the high temperature environment. In such embodiments, acoustic signals can be cross correlated to determine the approximate distance of the source of the alarm device, and an image reflecting the approximate distance of the source of the alarm device can be optionally displayed on a handheld device. In these embodiments, any suitable device may be used including but not limited to a personal alert safety system carried by firefighters. Such embodiments may be used to locate a downed fighfighter, robot, or to identify particular locations of interest in a high temperature environment. 
         [0037]      FIG. 3  illustrates an example obscured, high temperature environment that includes a wall at a remote location. As shown in system  300 , a high temperature environment includes a wall  302 , a fire  304 , and a handheld navigation system  306 . Wall  302  represents the distant wall forming the far boundary of an open room. As illustrated in obscured, high temperature environment  300 , fire  304  may be located near the middle of the room. In particular embodiments the fire may be of various power ratings. For example, in one particular embodiment, the fire may be a seven kilowatt fire, and in another embodiment, the fire may be a 43 kilowatt fire. While some figures illustrate specific fire power ratings, it should be understood that the teachings of the present disclosure can be used with fires of any power rating. 
         [0038]    Handheld navigation system  306  may represent a handheld device according to the present disclosure, such as described in system  100 . In operation, handheld navigation system  306  may transmit low frequency, long duration, frequency modulated signals towards wall  302 . For example, the transmitted signal may be a linear frequency modulated signal. In particular embodiments, the signal may be transmitted through the flames or smoke generated by fire  304 . The low frequency and long duration of the transmitted signals ensure that little or no interference occurs due to the high frequency turbulence that may be caused by the burning flames of an active fire  304 . In particular circumstances, the flames of fire  304  may be unpredictable and can change rapidly. However, the use of low frequency long duration signals facilitates transmission through fire  304  to wall  302 , with little or no artifacts resulting in the transmitted signals or the corresponding reflected signals. Handheld navigation system  306  may then collect reflections of the transmitted signal from wall  302 , whether using a path directly through flame  304  or otherwise, and cross correlate this information to the transmitted signal in order to determine an approximate location of the remote wall  302 . This information may then be displayed on the display of handheld navigation system  306  in a suitable format intelligible to the user. In other embodiments, handheld navigation system  306  may transmit sonar signals sweeping a range of frequencies that include both high and low frequencies. In those embodiments, the information from the reflected signals of both high and low frequencies may be used to determine, with higher precision, the characteristics of structures and the active flame. 
         [0039]    While system  300  is illustrated as including specific components, it should be understood that various embodiments may operate using any suitable arrangement and collection of components. 
         [0040]      FIG. 4  represents a color plot on a Cartesian coordinate system mapping distance in the Y-direction across the Y-axis and distance in the X-direction across the X-axis in an two-dimensional Cartesian coordinate system where (0, 0) represents the center of the room. As shown, system  400  depicts the obscured, high temperature environment of system  300  as characterized by a seven kilowatt fire and includes the calculated distance information determined on an appropriate handheld navigation system according to the techniques of the present disclosure. For example, system  400  includes an image of the fire  402  and the image of the remote wall  404 . As shown in system  400 , the image of fire  402  corresponds to the fire  304  in system  300 , and the image of the wall  404  corresponds to the wall  302  of the example obscured, high temperature environment in system  300 . 
         [0041]      FIG. 5  represents a color plot on a Cartesian coordinate system mapping distance in the Y-direction across the Y-axis and distance in the X-direction across the X-axis in an two-dimensional Cartesian coordinate system where (0, 0) represents the center of the room. As shown, system  500  depicts the obscured, high temperature environment of system  300  characterized by a forty three kilowatt fire and includes the calculated distance information determined on an appropriate handheld navigation system according to the techniques of the present disclosure. For example, system  500  includes an image of the fire  502  and the image of the remote wall  404 . As shown in system  500 , the image of fire  502  corresponds to the fire  304  in system  300 , and the image of the wall  504  corresponds to the wall  302  of the example obscured, high temperature environment in system  300 . 
         [0042]    While systems  300  and  400  are depicted as illustrating specific features of an obscured, high temperature environment, it should be understood that various embodiments may provide less or additional information regarding the obscured, high temperature environment using any suitable arrangement and collection of components. 
         [0043]      FIG. 6  is an example obscured, high temperature environment for detecting the location of a remote doorway in the obscured high temperature environment. As illustrated, an example obscured, high temperature environment is shown that includes a wall at a remote location. As shown in system  600 , the obscured, high temperature environment includes walls  602 , a doorway  604 , a fire  606 , and a handheld navigation system  608 . Walls  602  represent distant walls together forming a remote doorway  604  in between wall  602   b  and  602   c . As illustrated in obscured, high temperature environment  600 , fire  606  may be located near the middle of the room. In particular embodiments the fire may be of various power ratings, for example, in one particular embodiment, the fire may be a seven kilowatt fire and in another embodiment, the fire may be a 43 kilowatt fire. 
         [0044]    Handheld navigation system  608  may represent a handheld device according to the present disclosure, such as described in system  100 . In operation, handheld navigation system  608  may transmit low frequency, long duration, frequency modulated signals towards walls  602 . For example, the transmitted signal may be a linear frequency modulated signal. In particular embodiments, the signal may be transmitted through the flames or smoke generated by fire  606 . The low frequency and long duration of the transmitted signals ensure that little or no interference occurs due to the high frequency turbulence that may be caused by the burning flames of an active fire  606 . In particular circumstances, the flames of fire  606  may be unpredictable and can change rapidly. However, the use of low frequency long duration signals facilitates transmission through fire  606  to walls  602 , with little or no artifacts resulting in the transmitted signals or corresponding reflected signals. Handheld navigation system  608  may collect the reflections of the transmitted signal from walls  602 , whether using a path directly through flame  606  or otherwise, and cross correlate this information to the transmitted signal in order to determine an approximate location of each of the remote walls  602 . The determined distance and location of walls  602   a ,  602   b , and  602   c  enables the handheld navigation to determine the presence and location of a doorway between walls  602   b  and  602   c . The distance information may then be displayed on the display of handheld navigation system  608  in a suitable format intelligible to the user such that the presence and location of doorway  604  can be determined by the user despite the high temperature and low visibility presented by the extreme conditions of the environment. Such information may enable the user to determine the various structures in the room and appropriate exit paths, thereby facilitating safe and efficient navigation in the dangerous environment. 
         [0045]    While system  600  is illustrated as including specific components, it should be understood that various embodiments may operate using any suitable arrangement and collection of components. 
         [0046]      FIG. 7  illustrates a color plot of example results from using the handheld navigation system of the present disclosure in an obscured, high temperature environment having a forty-three kilowatt fire in a room with remote walls forming a doorway. As illustrated, system  700  represents a color plot on a Cartesian coordinate system mapping distance in the Y-direction across the Y-axis and distance in the X-direction across the X-axis in an two-dimensional Cartesian coordinate system where (0, 0) represents the present position of the handheld navigation system depicted in system  600 . As shown, system  700  depicts the obscured, high temperature environment of system  600  characterized by a forty three kilowatt fire and includes the calculated distance information determined on an appropriate handheld navigation system according to the techniques of the present disclosure. For example, system  700  includes an image of the fire  702  and the image of the remote walls  704 . As shown in system  700 , the image of fire  702  corresponds to the fire  606  in system  600 , and the images of the walls  704  correspond to the walls  602  of the example obscured, high temperature environment in system  600 . The image of the remote walls  704   b  and  704   c  together form the boundaries of the doorway that exists between them. In this manner, a user may determine the appropriate exits in a structure despite high temperatures and low visibility. 
         [0047]    While system  700  is depicted as illustrating specific features of an obscured, high temperature environment, it should be understood that various embodiments may provide less or additional information regarding the obscured, high temperature environment using any suitable arrangement and collection of components. Although only exemplary embodiments of the invention are specifically described above, it will be appreciated that modifications and variations of these examples are possible without departing from the spirit and intended scope of the invention. For example, throughout the specification particular measurements are given. It would be understood by one of ordinary skill in the art that in many instances, particularly outside of the examples, other values similar to, but not exactly the same as the given measurements may be equivalent and may also be encompassed by the present disclosure.