Patent Publication Number: US-2016249173-A1

Title: Method, device and system for navigating a site.

Description:
FIELD OF THE INVENTION 
     The present invention relates to the general field of navigation, and is more specifically concerned with a method, device and system for navigating a site. 
     BACKGROUND 
     Navigation in open spaces has become pervasive in recent years due to the integration of the global positioning system (GPS) devices in smart phones. However, the GPS signal is typically unavailable indoors. Accordingly, smart phones and order similar devices cannot be used typically indoors to guide people through unfamiliar sites. 
     Other signals, such as Wi-Fi and Bluetooth signals, are sometimes used to provide navigation on such sites. To that effect, signal emitters are provided at many locations on the site. However, such systems are relatively expensive, either due to the number of signal emitters required to completely cover a site, or to complexity of such signal emitters. 
     Accordingly, there exists a need for an improved method, device, and system for navigating a site. It is a general objective of the present invention to provide such an improved device, improved system and improved method. 
     SUMMARY OF THE INVENTION 
     In a broad aspect, the invention provides a method usable by an intended user for navigating a site using a navigation device, said site including beacons detectable by said navigation device, said method comprising: a) receiving from said intended user a destination on said site; b) detecting when said navigation device is adjacent of one of said beacons; c) determining an orientation of said navigation device; d) presenting to said intended user information indicative of a direction to take to reach said destination or another one of said beacons closer to said destination than said one of said beacons; e) repeating steps b to d until said user is at said destination. 
     Instead of using the strength of signals to triangulate the position of the intended user, the proposed method relies on a network of beacons providing a graph representing the site. Navigation from an initial location to a destination is made by navigating the graph or, in other words, by going from beacon to beacon. This type of navigation requires less precision than signal intensity-based navigation involving triangulation, and may also require the use of a smaller number of signal emitting devices. Indeed, taking for example the case of a very long corridor, there is no need to add beacons all along the corridor if there are no branches. All that is required is a beacon close to the entrance of the corridor and another one at the end of the corridor. 
     Other objects, advantages and features of the present invention will become more apparent upon reading of the following non-restrictive description of preferred embodiments thereof, given by way of example only with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings: 
         FIG. 1 , in a schematic view, illustrates a site to navigate using methods provided by the present invention; 
         FIG. 2 , in a block diagram, illustrates a navigation system usable on the site of  FIG. 1 ; 
         FIG. 3 , in a flowchart, illustrates a method of initialization to be performed to be able to navigate the site of  FIG. 1  using the navigation system of  FIG. 2 ; 
         FIG. 4 , in a flowchart, illustrates a method for performing a step of creating an orientation table that is part of the method of  FIG. 3 ; 
         FIG. 5 , in a flowchart, illustrates a method for associating orientations and destinations that is part of the method of  FIG. 4 ; 
         FIG. 6 , in a flowchart, illustrates a method for navigation the site of  FIG. 1  using the navigation system of  FIG. 2 ; 
         FIG. 7 , in a flowchart, illustrates a method for assisting a user in selecting a beacon among many detected beacons; 
         FIG. 8 , in a flowchart, illustrates a method for performing a step of displaying beacon symbols part of the method of  FIG. 7 ; 
         FIG. 9 , in a schematic view, illustrates a geometry usable for displaying beacon symbols in the method of  FIG. 8 ; 
         FIGS. 10A to 10C , in screen captures, illustrate beacon symbols corresponding to various distances with the corresponding beacons; and 
         FIG. 11 , in a schematic view, illustrates a relationship between a beacon symbol size and distance from the corresponding beacon usable in the method of  FIG. 8 . 
     
    
    
     DETAILED DESCRIPTION 
     With reference to  FIG. 1 , there is shown an example of a site  10  that will be used in the description of the present invention. While the site  10  represented in  FIG. 1  is in the form of a building, the present invention is usable in any suitable type of sites, including outdoor sites. Accordingly, while  FIG. 1  illustrates a site  10  including rooms, in other embodiments, the different locations on the site  10  may be any other suitable contiguous area of the site  10 . It should be understood that the site  10  is only for example purposes and does not limit the scope of the present invention. The site  10  includes a number of rooms  12 ,  14 ,  16 ,  18 ,  20  and  22 . Rooms  12  to  20  are for the purpose of this example relatively small. Room  22  is much larger than rooms  12  to  20 . The site is to be navigated by an intended user  24 , here represented in room  12 . Beacons  26  to  44  are provided in the rooms  12  to  22  and in some embodiments in at least some of the corridors  46  to  54  linking the rooms  12  to  22  to each other, for example at intersection  58 . 
     Corridor  46  extends between rooms  12  and  22 . Corridor  48  extends between rooms  20  and  22 . Corridors  50 ,  52 ,  54  and  56  extend respectively from rooms  14 ,  16 ,  18  and  22  and all intersect at intersection  58 . Beacons  26 ,  28 ,  30  and  34  are provided respectively in rooms  12 ,  14 ,  16  and  20 . Beacons  38  to  44  are all provided in the room  22 , for example each in a respective quadrant thereof. Beacon  36  is located at intersection  58 . For the purpose of this example, rooms  14 ,  16  and  18 , along with corridors  50 ,  52 ,  54  and  56  form a region  60 , the purpose of which will be described in further details hereinbelow. A region  60  for the purpose of this document includes a section of the site  10 , typically contiguous, used to facilitates navigation, typically in large sites  10 . 
     Beacons  26  to  44  are devices that emit a signal, typically a radio frequency signal, to be picked up by a suitable navigation device  102  illustrated in  FIG. 2  and described in further details hereinbelow. The signal includes information allowing identification of the specific beacon  26  to  44  that emits the signal. It should be noted that other types of signals are usable with the present invention, including for example ultrasound signals, among others. A specific embodiment of the beacons  26  to  44  includes Bluetooth beacons, and more specifically Bluetooth low energy (BLE) beacons. BLE beacons are devices that emit simple Bluetooth signals, consisting of an identifier of the beacon. This identifier may be unique to the beacon or shared by a number of beacons. The power with which the signal is emitted may be adjusted or set, but is not varied once adjusted. BLE beacons are well known in the art and will not be described in further details hereinbelow. The reader skilled in the art will understand that other suitable types of beacons, including but not limited to other types of Bluetooth beacons or Wi-Fi beacons are usable with the present invention. 
     In the example shown in  FIG. 1 , rooms  12 ,  14 ,  16  and  20  are relatively small. Accordingly, only one beacon  26 ,  28 ,  30  and  34  is required in each of these rooms  12 ,  14 ,  16  and  20  as the signal emitted by this beacon  26 ,  28 ,  30  and  34  is powerful enough to be detected over the whole room  12 ,  14 ,  16  and  20 . It should be near noted that in some embodiments, no beacon is provided in at least some rooms, for example as in room  18  in  FIG. 1 . Room  22  is a relatively large room so that using only one beacon would not ensure coverage of the whole room  22 . Accordingly, four beacons  38 ,  40 ,  42  and  44  are used to ensure that the navigation device  102  will pick up a signal at any location in the room  22 . The four beacons  38 ,  40 ,  42  and  44  may all broadcast the same identifier or different identifiers. In the first case, only determination that one is located within the room  22  may be made. In the second case, a more precise location of the specific portion of the room  22  in which the intended user  24  may be located is made possible. 
       FIG. 2  illustrates in a block diagram a navigation system  100  usable on site  10 . The navigation system  100  includes a navigation device  102  and a server  104 . The navigation device  102  is usable both to navigate the site  10  and to initialize the navigation system  100  so that the navigation system  100  may be used to navigate the site  10 . Typically, different physical navigation devices  102  having similar hardware are used to initialize the navigation system  100  and to navigate the site  10 , but in other embodiments the same navigation device  102  is used for both actions. 
     The navigation device  102  includes a Central Processing Unit (CPU)  122  connected to a memory unit  124  over a data bus  126 . Although the memory unit  124  is shown as a single block, it may include a plurality of separate components, such as Read Only Memory (ROM), Random Access Memory (RAM), flash memory, or a hard disk, among others. The navigation device  102  also includes a user interface  128  usable by the intended user  24 , a signal detector  106  and a compass  108  that all connect to the data bus  126 . When the navigation device  102  is in use, the memory unit  124  holds a program element executed by the CPU  122 , the program element implements one or more of methods  200  to  700  described hereinbelow. In some embodiments, a network interface  130 , such as a wireless network interface (for example a Wi-Fi interface), is also part of the navigation device  102  and communicates with the CPU  122  and/or the memory unit  124  through the data but  126 . 
     The intended user  24  communicates with the navigation device  102  through the user interface  128 . In a non-limiting example of implementation, the user interface  128  includes a touch screen. The user interface  128  is configured both to communicate information to the intended user  24  and to receive inputs therefrom, for example to receive input data therefrom or to control the operation of a program element executed by the CPU  122 . The user interface  128  may include in some embodiments, for example, any one or a combination of the following: display unit, camera, keyboard, pointing device, touch sensitive surface or speech recognition unit, among others. 
     The signal detector  106  includes hardware and software required to detect and characterize the signals emitted by the beacons  26  to  44 . For example, the beacons  26  to  44  emit radio-frequency signals and the signal detector  106  includes an antenna, amplifiers and circuitry required to detect the intensity of the signal received and decode its contents. The signal may be analog or digital, depending on the embodiment of the invention. This intensity and contents may be provided to the CPU  122  through the data bus  126 . In some embodiments, directional information indicating the direction from which a signal is emitted relative to the navigation device  102  may also be similarly provided. Typically, the signal detector  106  is able to receive signals from many of the beacons  26  to  44  and separate these signals from each other. 
     The compass  108  detects the orientation of the navigation device  102  relative to a reference orientation. The compass  108  may use a magnetometer and/or inertial detection to provide heading, and in some embodiments roll and pitch information. Orientation information is provided to the CPU  122  over the data bus  126 . 
     The server  104  is typically a general-purpose computer having a network interface. The server  104  may communicate with the network interface  130  to exchange information with the navigation device  102 . The architecture of the server  104  is typically similar to that of the navigation device  102 , except that usually no compass  108  and signal detector  106  is provided therein. In some embodiments, no server  104  is required to operate the navigation system  100  as all data is stored on the navigation device  102 . 
     There are two steps in the use of navigation system  100 . The first step is initialization that must be performed when a site  10  is first setup. The second step is navigation which is performed once initialization has been performed. Initialization is performed through initialization method  200  shown in  FIG. 3 . Navigation is performed through navigation method  500  shown in  FIG. 6 . 
     Referring to  FIG. 3 , there is shown the initialization method  200 . Initialization method  200  starts at step  205 . Then, at step  210 , the beacons  26  to  44  are deployed. Subsequently, at step  215 , a destination list is created and at step  220 , an orientation table is created. Finally, the method ends at step  225 . The initialization method  200  may be performed on a site  10  that previously did not include any beacon  26  to  44 , or to add beacons  26  to  44  to a site that previously included such beacons  26  to  44 , or to modify a site  10 , with or without moving any of the beacons  26  to  44 . 
     At step  210 , the beacons  26  to  44  are deployed on the site  10 . The beacons  26  to  44  are first programmed to broadcast an identifier identifying each beacon  26  to  44 . The beacons  26  to  44  may all have different identifiers, or some subgroups of the beacons  26  to  44  may share a common identifier. In some embodiments, the power with which the identifier is broadcast can be also programmed. Then, the thus programmed beacons  26  to  44  are physically located at suitable locations on the site  10 . Typically, the beacons  26  to  44  are located at locations at which the intended user  24  needs to make a choice while navigating the site  10 , or at locations from which the intended user  24  may start or finish navigation on the site  10 . Positioning of the beacons  26  to  44  is selected so that the navigation device  102  can easily detect them with high reliability. Deployment of the beacons  26  to  44  may be made using empirical rules, simulators indicating the power of their signal in on the site  10  or through trial and error using the navigation device  102  to detect power of the signal emitted by each beacon  26  to  44  as they are deployed at many locations on the site  10 . 
     At step  215 , the destination list is created. Destinations are locations on the site  10  that the intended user  24  may wish to reach. For example, rooms  12 ,  14 ,  16 ,  18  and  20  may be destinations. In another example, the destination is a portion of a room, such as the corner of room  22  closest to the beacon  42 . Destinations may be located on different floors in a building. Destinations are created at initialization, not by the intended user  24  wishing to navigate the site  10 . The intended user  24  selects from the destination list when navigating, as described in further details hereinbelow. The destination list is stored on the server  104  and/or in the memory unit  124 . The destination list includes information characterizing each destination, such as a name in alphanumeric characters. The destination list may also include other information, such as a picture of the destination. The destination list may be created on the navigation device  102  using the user interface  128 , or using any other device, such as the server  104  or another computer, laptop or tablet. In some embodiments, there are many destinations that are close to each other. These destinations could be grouped in a region, such as region  60  for the site  10 . Step  215  may then include creating a list of such regions  60 , the list also including the destinations that are within each region  60 . The purpose of regions  60  is detailed hereinbelow. 
     At step  220 , an orientation table is created. The orientation table includes information indicative of a direction towards which the intended user  24  needs to move to reach each destination, or at least a subset of the destinations, when each of the beacons  26  to  44  is reached. Step  220  is illustrated in  FIG. 4  which includes a flowchart of an example of an orientation table creation method  300 . 
     Method  300  starts at step  305 . Then, at step  310 , the intended user  24  moves towards one of the beacons  26  to  44  for which no orientation data is available while carrying the navigation device  102 , or a beacon  26  to  44  for which orientation data must be added, removed or altered. Then, at step  315 , when the intended user  24  approaches one of the beacons  26  to  44 , say for example beacon  36 , the navigation device  102  picks up the signal emitted by the beacon  36  using the signal detector  106  and indicates to the intended user  24 , using the user interface  128 , that the beacon  36  is in proximity to the intended user  24 . Then, at step  320 , the intended user indicates to the navigation device  102 , through the user interface  128 , that the beacon  36  is to be selected. Subsequently, at step  325 , the intended user  24  associates an orientation with at least some destinations from the destination list for the beacon  36 . If the beacon  36  reached is at one of the destinations from the destination list, this information is entered in the orientation table instead of entering directions. At step  330 , the intended user determines if all beacons on the site  10  have been entered in the destination list. If not, the method  300  loops back to step  310 . Otherwise, the method proceeds to step  335  to store the orientation table on the server  104 , if needed, and then ends at step  340 . 
     Step  315  involves many activities in the navigation device  102 . In some embodiments, the signal detector  106  sends to the CPU  122  information indicative of all beacons  26  to  44  within detection range, including the intensity of the signal detected for each and their identifier, and the CPU  122  processes this information to select the beacon  36  closest to the intended user  24 , that is usually the beacon  26  to  44  for which the signal intensity is the largest. In some embodiments, the CPU  122  further applies a threshold to the signal intensity so that the beacon  36  is considered detected if the signal intensity is above a predetermined threshold. In other embodiments, no such processing is required as the intended user  24  will move by himself adjacent the beacon  36  as the location of the beacon  36  is known. 
     Regarding step  320 , in some embodiments, determination that a certain beacon  36  has been reached is made automatically by the navigation device  102 , for example using thresholding as described hereinabove, and this beacon  36  is automatically selected. In other embodiments, information, such as signal intensity and identifier, regarding one, some, or all of the beacons  26  to  44  detected is presented to the intended user  24  through user interface  128  and the intended user selects which beacon  36  will be used for the moment to enter corresponding orientation data. This presentation and selection may also be made using the selection method  600  presented in  FIG. 7 . 
     Step  335  is optional as the orientation table may be stored in memory unit  124 . However, in some embodiments, it is convenient to store the orientation table on a server  104  so that it can be accessed later depending on which site  10  the intended user  24  is, and so that updates to the orientation table can be presented. 
     Method  400 , shown in  FIG. 5 , may be used at step  325 . Method  400  starts at step  405 . Then, at step  410 , the intended user  24  faces an orientations towards which the intended user  24  must move to reach at least one of the destinations. Once the intended user  24  faces this orientation, at step  415 , the intended user  24  indicates through the user interface  128  that this orientation at the selected beacon  36  is to be selected. The orientation is detected using the compass  108 . In some embodiments, step  420  allows selection of a type of access associated with the destination and, if applicable, entry of auxiliary information is made through the user interface  108 . Then, at step  425 , the intended user uses the user interface  128  to select which one, or which ones, of the destinations is to be associated with the orientation selected at step  415  in the orientation table. Afterward, at step  430 , the intended user  24  indicates to the navigation device  102 , through the I/O interface  128 , if there are more orientations to select for the specific beacon  36  at which the intended user  24  is located, which results in the method  400  looping back to step  410 , or if the intended user  24  may move to another beacon  26  to  44 , at which point method  400  ends. 
     Step  420  includes adding information related to actions that the intended user  24  should take to reach a destination using navigation device  102 . For example, in some embodiments, the user interface  128  is used to take a picture of a specific feature towards which the intended user  24  would move to reach the destination. For example, if reaching the destination requires going through an elevator, step  420  may include taking a picture of this elevator to be stored in the orientation table also. Also, auxiliary information could be entered using the user interface  128 , such as textual information providing information of where the intended user should go. For example, if the intended user  24  should take the elevator to reach the destination, a message indicating that the elevator should be taken up to the 3 rd  floor, for example, could be entered and stored in the orientation table. It should be noted that the orientation may point directly towards the destination or the orientation may point towards another beacon  26  to  44  towards which the intended user must move to reach the destination. Therefore, for each beacon  26  to  44 , there is a list of destinations and for each destination, a specific orientation is stored. The orientation table contains all information that is thought to be necessary for the intended user  24  to navigate to the destinations from the beacon  36 . 
     In some embodiments, there are many destinations that are close to each other. These destinations could be grouped in a region, such as region  60  for the site  10 . Then, instead of indicating in the orientation table all destinations reachable from each beacon  26  to  44 , when the intended user  24  is outside of the region  60 , only the region  60  needs to be specified and the navigation device  102  may either use this region information while navigating so that all destinations within the region  60  are treated similarly, or the navigation device  102  may populate the orientation table with all destinations within the region  60  without the intended user entering all these destinations. For example, for beacon  40 , rooms  14 ,  16  and  18  are within region  60 . When at beacon  40 , the intended user  24  would point towards the access to corridor  56  and indicate that the corresponding orientation is associated with region  60 . Later, when navigating the site  10 , the intended user  24  will be told through the navigation device  102  to go towards corridor  56  when the destination is any one of rooms  14 ,  16  and  18 . 
     Once all beacons  26  to  44  have been visited, initialization is complete and the intended user  24  may perform navigation method  500  shown in  FIG. 6 . It should be noted that the intended user  24  typically changes between methods  200 , in which the intended user  24  is for example an employee performing method  200 , and the method  500  in which the intended user  24  is for example a visitor of the site  10 . 
     Method  500  starts at step  505 . Then, at step  510 , the orientation table for the site  10  is downloaded by the navigation device  102  from the server  104  through the network interface  130 . Subsequently, at step  515 , the navigation device  102  detects one or more beacons  26  to  44  and one of the beacons  26  to  44  is selected. Then, at step  520 , the orientation table data is displayed to the intended user  24  for the selected beacon by displaying one or more destinations reachable from the beacon  26  to  44  selected at step  515 , and the intended user  24  selects one of these destinations at step  525 , steps  520  and  525  being performed using the user interface  128 . Once a destination is selected, at step  530 , the orientation towards which the intended user should move to reach the selected destination is displayed using the user interface  128 , along with any pictures and/or auxiliary data associated with this destination. Afterward, at step  535 , if the destination is not reached or reachable following the displayed information, method  500  loops back to step  515 . Otherwise, method  500  goes to step  540 , at which point method  500  ends. 
     In step  510 , the orientation table could be downloaded for the whole site  10 , or only for beacons  26  to  44  detectable by the navigation device  102 . Also, in some embodiments, only orientation table data associated with beacons  26  to  44  within detection range by the signal detector  106  is downloaded. In these embodiments, steps  510  and  515  are reversed with step  515  being performed before step  510 . In yet other embodiments, the orientation table for site  10  is already stored in the memory unit  106  and does not need to be downloaded, so that step  510  is omitted. 
     In step  515 , the navigation device  102  uses the signal detector  106  to provide to the CPU  122  information regarding one or more beacons  26  to  44  detectable using the signal detector  106 . One of these beacons  26  to  44  is selected as being the one for which orientation data is to be provided. In some embodiments, selection of the beacon  26  to  44  is made automatically by the navigation device  102 , for example using thresholding to identify a beacon  26  to  44  for which the intensity of the signal is above a predetermined threshold selected to indicate proximity to the beacon  26  to  44 . In other embodiments, information, such as signal intensity and identifier, regarding one, some, or all of the beacons  26  to  44  detected by the signal detector  106  is presented to the intended user  24  through I/O interface  128  and the intended user selects which beacon  26  to  44  will be selected using the I/O interface  128 . This presentation and selection may be made for example using the selection method  600  presented in  FIG. 7 . 
     In step  520 , the orientation table data from the orientation table for the selected beacon  26  to  44  is presented. For example, all access points through which the intended user  24  must pass to reach one or more destinations are displayed on a display part of the user interface  128 , along with identification of one or more destinations reachable through the access point. Examples of access points include doors, elevators and corridors, among others. The access points are in some embodiments displayed in list format. In other embodiments, the navigation device  102  uses the orientation of the navigation device  102  obtained from the compass  108  to display the access points roughly according to the direction towards which the intended user  24  should move to reach them. For example, a schematic or exact plan of the location surrounding the beacon  26  to  44  selected is displayed with the beacon  26  to  44  selected at the center of the display, and access points roughly or exactly where they are in space, in orientation and/or distance on the plan relative to the beacon  26  to  44 . Then, the intended user may select which destination is to be reached, for example by tapping on the part of a touch screen part of the user interface  128  showing a symbol or characters indicative of this destination. It should be noted that in some embodiments, the destination is selected once in the whole navigation process and only access point and orientation table data corresponding to this destination is displayed at step  520 . Step  525  then becomes unnecessary. 
     At step  530 , the navigation device  102  uses the compass  108  to determine the orientation of the navigation device  102  and displays to the intended user  24  a direction towards which the intended user  24  should move to reach the selected destination. For example, an arrow pointing towards the direction towards which the intended user  24  should move to reach the selected destination is displayed on a display part of the user interface  128 . Also, in some embodiments, the access point corresponding to the selected direction could be highlighted on the plan used in step  520 . If available, a photograph of the access point and auxiliary information may also be provided on the display. 
       FIG. 7  illustrates a method  600  performed by the navigation device  102  to allow selection of one of the beacons  26  to  44  when many beacons  26  to  44  are within detection range. Method  600  is usable in methods  300  and  500  at steps  320  and  515 , respectively, as mentioned hereinabove. However, method  600  is usable in any other context wherein there is a need of selecting a beacon when many are detected. Generally speaking, method  600  represents all or some of the detected beacons  26  to  44  on a display by displaying a symbol for these beacons  26  to  44  detected along a line extending between the center of a polygon and a vertex of the polygon. Each beacon is associated with a respective vertex. 
     More specifically, method  600  starts at step  605 . Then, at step  610 , the navigation device  102  scans for beacons  26  to  44  detectable using the signal detector  106  and associates with the identifier of each detected beacon  26  to  44  an estimated distance at step  615 . Steps  610  and/or  615  may be omitted if the information they provide is already available, for example if method  600  is part of a more complex method. Afterward, at step  620 , up to a maximal number of beacons  26  to  44  are selected and beacon symbols  804  corresponding to these beacons  26  to  44  are displayed on the user interface  128  of the navigation device  102  at step  625 . Then, at step  630 , the navigation device  102  determines if one of the beacon symbols  804  is selected by the intended user  24 , for example by detecting that of one of the beacon symbols  804  displayed at step  625  has been tapped on a touch screen part of the user interface  128 . If the beacon symbol  804  corresponding to one of the beacons  26  to  44  is selected, the method continues to step  635 , at which point the method ends. Otherwise, the method loops back to step  610  to update if required the detected beacons list. When appropriate, after the method  600  has ended, a predetermined action associated with the beacon  26  to  44  associated with the selected beacon symbol  804 . 
     Step  610  is performed using method well known in the art. For example, most Bluetooth enabled devices, such a the navigation device  102  in the form of a smart phone, for example, include the necessary software and hardware to detect other Bluetooth devices, for example with the beacons  26  to  44  taking the form of BLE beacons. 
     At step  615 , for each detected beacon  26  to  44 , the intensity of the signal is used to estimate a distance between the beacon  26  to  44  and the navigation device  102 . It should be noted that in some embodiments, this distance estimate may have a relatively large error without unduly affecting the method  600 . The distance is not used per se to determined the position of the navigation device  102  relative to the beacons  26  to  44 , for example using triangulation. This distance is only used to select which beacons  26  to  44  are close to the navigation device  102  so that information related thereto can be displayed to the intended user  24 . In some embodiments, the distance is simply estimated using a power law in which the distance is inversely proportional to a power of the signal intensity, for example to the square of the signal intensity. In other embodiments, the distance estimate uses previously acquired empirical data related to each beacon  26  to  46  so that the distance takes into account the electromagnetic properties of the environment of the beacon  26  to  44  and the specific shape of the electromagnetic field emitted by the beacon  26  to  44 . The previously acquired data maps the signal intensity for each beacon  26  to  44  as a function of distance from the beacon  26  to  44 . For example, one factor that may affect distance determination is the angular orientation relationship between the broadcasting antenna of the beacons  26  to  44  and the receiving antenna of the signal detector  106 , which affects the intensity of the signal detected by the signal detector  106 . Once the orientation of the broadcasting antenna is known, the compass  108  may provide an indication of the spatial orientation of the receiving antenna. Using this information, the estimated distance between the beacon  26  to  44  and the navigation device  102  may be better determined by introducing a corrective factor dependent on the relative orientation between the broadcasting and receiving antennas. The orientation of the broadcasting antenna may be determined either theoretically, taking into account the position and physical orientation of the beacons  26  to  44 , or empirically when the site  10  is first setup by using a suitable detector, such as the signal detector  106 , which may be used to characterize the electromagnetic field emitted by the broadcasting antenna, which depends on the orientation of the broadcasting antenna. Similar improvements in distance estimation may also be used at any other steps described in the present document wherein a distance between the navigation device  106  and a beacon  26  to  44  is determined. In yet other embodiments, the signals from all beacons  26  to  44  detectable at a certain location are used to determine, again using empirical data, the distance to each beacon  26  to  44 . For example, a beacon  26  to  44  located around a corner may only be weakly detected. However, for example, previous information about other beacons  26  to  44  may indicate that when a certain subset of those beacons  26  to  44  is detected, a weak signal from the beacon  26  to  44  that is just around the corner indicates that in fact this beacon  26  to  44  is close to the navigation device  102 , and that the corresponding distance thereto is small. 
     At step  620 , all the identified beacons  26  to  44  are sorted, for example in order of decreasing distance from the navigation device  102 , and only up to a predetermined number of these beacons  26  to  44  are selected for use in step  625 . It should be noted that if method  600  is iterated repeatedly, it may be advantageous to depart from a strict “minimal distance” criteria to select beacons  26  to  44 . Indeed, in some embodiments, due to the nature of the signal emitted by the beacons  26  to  44 , the signal intensity may vary rapidly in time, for example when people and objects move between the navigation device  102  and the beacons  26  to  44 . In these embodiments, it may be advantageous to select beacons  26  to  44  that are not the closest, but which were previously selected, for a predetermined duration after they have moved out of the list of closest beacons. The predetermined duration may be for example one, two or  5  seconds, among other possibilities. The same may be applied to beacons  26  to  44  that were previously detected, but that are subsequently undetected. In these embodiments, it may be advantageous to keep on selecting these beacons  26  to  44  for a predetermined number of iterations of the method  600 , or for a predetermined duration. In some embodiments, a visual indication is provided to the intended user  24  to indicate that a certain beacon is no longer detected, for example by blinking the beacon symbol  804  associated therewith. 
     Step  625  displays on the use interface  128  symbols for all the beacons  26  to  44  selected at step  620 . While in theory the identifier of the beacons  26  to  44  could be displayed, this would be highly user unfriendly. Instead, the beacons  26  to  44  are represented as symbols having identical, similar or different shapes. For example, in a method  700  described in further details hereinbelow, the beacons  26  to  44  are displayed as disks filled with a picture related to the beacon  26  to  44 . The picture may for example show the location at which the beacon is located. In other embodiments, the picture is related to an action to be performed by the navigation device  102  once the symbol corresponding to one of the beacons  26  to  44  is selected. In yet other embodiments, the symbol includes alphanumeric characters related to the location of the beacon  26  to  44 . 
       FIG. 8  is a flowchart of an example of a method  700  usable for displaying beacon symbols  804  at step  625  of method  600 . With reference to  FIG. 9 , a predetermined maximal number of beacon symbols  804  is displayed according to a polygonal geometry  800  having a number or vertices equal to the predetermined maximal number. In the example shown in  FIG. 9 , this predetermined maximal number is 6 and the beacon symbols  804  are displayed on an hexagonal geometry. More specifically, each beacon symbol  804  is associated with a vertex  802  of the polygonal geometry  800 . The beacon symbols  804  are in this embodiment disc shaped, but other suitable shapes are within the scope of the invention. Also, the beacon symbols  804  are all disc shaped, but it is within the scope of the invention to have symbols  804  having shapes differing from each other. 
     Distance between the navigation device  102  and each selected beacon  26  to  44  is conveyed in two manners. First, closer beacons  26  to  44  are represented by beacon symbols  804  having larger dimensions, such as larger diameters. Second, the distance between the beacon symbol  804  and the center of the hexagonal geometry  800  increases for closer beacons  26  to  44 . Each beacon symbol  804  is positioned along a radius  806  of the polygonal geometry  800  intersecting a respective vertex  802 . In some embodiments, the radius  806  of the beacon symbol  804  is selected so that each beacon symbol  804  remains confined within one sector  808  from a plurality of equal size sectors  808  each centered on a respective vertex  802 . 
     The relationship between beacon symbol size, for example radius, and distance to beacon  26  to  44  may be linear with or without upper and lower limits. However, it is often more important to clearly distinguish between the beacons  26  to  44  that are closest to the navigation device  102 . To that effect, the symbol size—distance from beacon relationship may be as seen in  FIG. 11 . First, all beacons  26  to  44  closer than a predetermined minimal distance, as estimated, are represented by bacon symbols  804  having predetermined maximal size. This is the case in the screen capture of  FIG. 10B , in which  6  beacons are all closer than the predetermined minimal distance. Similarly, all beacons  26  to  44  farther than a predetermined maximal distance, as estimated, are represented by beacon symbols  804  having a predetermined minimal size. This is the case in the screen capture of  FIG. 10B , in which  6  beacons are all farther than the predetermined maximal distance. Also, a predetermined intermediate distance is defined. The symbol size—distance from beacon relationship is linear between the predetermined minimal and intermediate distances. The symbol size—distance from beacon relationship is also linear between the predetermined maximal and intermediate distances, but with a different slope. A larger slope is selected for the beacons  26  to  44  closer than the predetermined intermediate distance, which enhances visually the distance variations with closest beacons  26  to  44 . In other embodiments, any other suitable symbol size—distance from beacon relationship may be selected. For example, a sigmoid shape could be used, which would result in a smoothed version of the symbol size—distance from beacon relationship illustrated in  FIG. 11 . 
     In a very specific and non-limiting example, the beacons  26  to  44  are BLE beacons and the predetermined minimal, intermediate and maximal distances are  0 . 5 ,  3  and  6  meters respectively 
       FIG. 10A  illustrate a case in which all beacon symbols  804  have the minimal size.  FIG. 10B  illustrate a case in which all beacon symbols  804  have the maximal size.  FIG. 10C  illustrate a more common case in which beacon symbols  804  have different dimensions. It should be noted that if the number of beacon symbols  804  to display is smaller than the number of vertices  802  of the polygon  800 , some sectors  808  remain empty. 
     Returning to  FIG. 8 , method  700  is now described in further details. Method  700  starts at step  705 . Then, at step  710 , one of the beacons  26  to  44  selected at step  620  of method  600  is selected for processing. A vertex  802  corresponding to an unoccupied radius of the polygon  800  is selected at step  715 . If method  700  is performed after is has been performed previously, it is advantageous, but not required, that the vertex  802  corresponding to a specific beacon  26  to  44  does not change between iterations of the method  700 . At step  720 , the distance from center along the radius  806  extending to the selected vertex  802  is computed, for example using the relationship of  FIG. 11 , to determine the symbol size and the appropriate location on the radius  806  is selected so that the symbol  804  is as close to the center of the polygon  800  while remaining entirely within one of the non-overlapping sectors  808 . Alternatively, a predetermined distance from center—distance from beacon relationship is used. Then, at step  725 , the symbols  804  are displayed along the selected radius  806  at the distance from the center determined in step  720  and scaled to the right symbol dimension using the predetermined symbol size—distance from beacon relationship, such as the one illustrated in  FIG. 11 , for example. At step  730 , if beacon symbols  804  for all selected beacons  26  to  44  have been displayed, method  700  ends at step  735 . Otherwise, method  700  loops back to step  710 . 
     Although the present invention has been described hereinabove by way of preferred embodiments thereof, it can be modified, without departing from the spirit and nature of the subject invention as defined in the appended claims.