Abstract:
Devices, methods and systems are disclosed herein to describe a range marker for a navigation system. The range marker may delineate a bounded area within a navigation map that a vehicle may travel based on the amount of fuel remaining. As the fuel continues to decrease during operation of the vehicle, the range marker may become smaller and smaller indicating a shrinking range since the fuel remaining decreases, thereby allowing the driver to easily identify which gas stations may be within a range of the vehicle (based on a current vehicle fuel level) and which gas stations might not be within the range of the vehicle.

Description:
BACKGROUND 
       [0001]    1. Field 
         [0002]    The present disclosure relates to navigation systems operating in conjunction with motor vehicles, and more particularly relates to methods, devices and systems for displaying a range marker for a navigation system. 
         [0003]    2. Description of the Related Art 
         [0004]    Over the last decade or so, navigation systems, and in particular, those based on a Global Positioning System (GPS), have become popular and extensively used in consumer vehicles and the like. A navigation system that allows a driver to focus on the road without having to look on paper maps while driving, helps prevent a driver from getting lost, and otherwise enhances the driving experience. In typical usage, the driver or another occupant inside the vehicle inputs the destination name or address via an interface (e.g., a LCD screen) on the navigation system. Once the address is ascertained, the navigation system quickly maps out the preferred route and provides instructions verbally or displays the instructions on a map or a screen, or both. As the driver begins driving the vehicle, the navigation system may provide turn-by-turn directions, verbally instructing the driver which road to stay on, which exit to take, where to make a turn, and the like, thereby assisting the driver to more efficiently arrive at the desired destination. Should the driver not follow the instructions given, some navigation systems are now able to re-route the driver in real-time, providing an updated route and corresponding instructions. 
         [0005]    While sophisticated, and certainly a welcome addition to vehicles, navigation systems are still not optimal. For example, consider the situation where a driver is searching for a nearby gas station as the fuel tank is approaching empty. Current navigation systems may display a plurality of gas stations, but the driver might not be able to determine which gas stations are reachable before the vehicle runs out of gas and may select a gas station that is out of range, leaving the driver stranded without gas prior to reaching the gas station. Moreover, as gas stations may be popular, a search for gas stations on the navigation unit may return too many results and may inundate the navigation screen with any and all gas stations displayable, thereby overwhelming or confusing the driver with too many displayed options. Accordingly, devices, systems and methods are needed to improve upon current navigation systems. 
       SUMMARY 
       [0006]    Devices, methods and systems are disclosed herein to describe a range marker for a navigation system. The range marker (herein used interchangeably with the term “range ring”) may delineate a bounded area within a navigation map that the vehicle may travel within prior to running out of gas, electricity or any other type of fuel powering the vehicle. For example, if the vehicle has enough gas left to drive 5 miles, then the range marker may be, in one embodiment, a circular ring with a radius of 5 miles since the vehicle may travel 5 miles in any direction without running out of fuel. As the fuel continues to decrease during operation of the vehicle, the range marker may become smaller and smaller indicating a shrinking range as the fuel remaining decreases. In one example, all refueling stations (e.g., gas stations, electronic depots, etc.) within the range marker may appear on the display of the navigation system, and as the location of the vehicle, the remaining fuel, and the reachable refueling stations change, the refueling stations that are out of range based on the remaining fuel may be removed from the display of the navigation system. 
         [0007]    In one embodiment, a navigation system is hardwired to the vehicle control system. In one example, a vehicle, especially those of a newer make and model year, may include an original equipment manufacturer (OEM) navigation system. These navigation systems are integrated into the vehicle (e.g., permanently or semi-permanently attached to the central console area and might not be removable for portable use). 
         [0008]    In another embodiment, a navigation system includes a data transmission wire, such as a universal serial bus (USB) for coupling the navigation system to the vehicle control system. The navigation system in this embodiment may be a third-party navigation system and may be portable (e.g., easily attachable or removable each time the driver enters and operates the vehicle). 
         [0009]    In another embodiment, a navigation system includes a wireless transmitter for communication with a vehicle control system. For example, the navigation system and the vehicle control system may communicate with each other via BLUETOOTH. The navigation system in this embodiment may be a third-party navigation system and may be portable (e.g., easily attachable or removable each time the driver enters and operates the vehicle). 
         [0010]    In another embodiment, a navigation system includes a wireless transceiver for communication with other wireless transceivers (e.g., a BLUETOOTH transceiver). However, if the vehicle does not have a wireless transceiver but has a physical interface for receiving an external input (e.g., a USB port), a physical drive with BLUETOOTH and physical connection capabilities (e.g., a USB adapter) may be used, among other functions, as an intermediary to transmit data between the navigation system and the vehicle. The navigation system and the physical drive in this embodiment may be third-party systems and may be portable (e.g., easily attachable or removable each time the driver enters and operates the vehicle). 
         [0011]    In another embodiment, the physical devices and systems described herein may perform the following method. First, the navigation system may receive an input to display nearby refueling stations. Next, the navigation system may obtain information from the vehicle indicating the distance that the vehicle is estimated to be able to travel before running out of fuel (“distance to empty”). Based on the distance to empty information, the navigation system may determine a size of the ring marker and the refueling stations within the ring marker. The navigation system may then display the ring marker and refueling stations. As the vehicle is operated and fuel is consumed and reduced, the navigation system may decrease the area bounded by the ring marker and remove the refueling stations outside the ring marker if they are no longer within driving range of the vehicle. After the driver refuels the vehicle, the ring marker and refueling stations may be removed and the navigation system may revert back to normal operation mode. 
         [0012]    In yet another embodiment, the physical devices and systems described herein may perform the following method. The navigation system may be operating in a standard mode. Once the distance to empty is below a certain threshold (e.g., 10 miles, 1 gallon of fuel remaining, 30 minutes of charge remaining, etc.), the navigation system may activate a range ring mode, which adds a range marker or range ring delineating the outside boundary of the range of travel based on the amount of fuel or charge left. The navigation system may also display the refueling or recharging stations within the boundary. As the vehicle continues to consume fuel or battery power, the range marker may get smaller and smaller until the vehicle is refueled or recharged. After the vehicle is refueled or recharged and the distance to empty is above the threshold, normal operation of the navigation system is resumed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    The features, obstacles, and advantages of the present invention will become more apparent from the detailed description set forth below when taken in conjunction with the drawings, wherein: 
           [0014]      FIG. 1  depicts an integrated navigation system within a vehicle according to one or more embodiments described herein; 
           [0015]      FIG. 2  depicts a third-party navigation system in communication with a vehicle according to one or more embodiments described herein; 
           [0016]      FIG. 3  illustrates an example of a screenshot of a navigation display with a range marker and gas stations according to one or more embodiments described herein; 
           [0017]      FIG. 4  depicts a block diagram of a navigation system in communication with a vehicle according to one or more embodiments described herein; 
           [0018]      FIG. 5  depicts a block diagram of a navigation system in communication with a vehicle according to one or more embodiments described herein; 
           [0019]      FIG. 6  depicts a block diagram of a navigation system in communication with a vehicle according to one or more embodiments described herein; 
           [0020]      FIG. 7  depicts a block diagram of a navigation system in communication with a vehicle according to one or more embodiments described herein; 
           [0021]      FIG. 8  illustrates an example of a flowchart describing an operation of a navigation system according to one or more embodiments described herein; 
           [0022]      FIG. 9  illustrates an example of a flowchart describing an operation of a navigation system according to one or more embodiments described herein; 
           [0023]      FIG. 10  illustrates a screenshot of a navigation display with a range marker and gas stations according to one or more embodiments described herein; 
           [0024]      FIG. 11  illustrates a screenshot of a navigation display with a range marker and a gas station according to one or more embodiments described herein; 
           [0025]      FIG. 12  illustrates a screenshot of a navigation display with a range marker and a gas station according to one or more embodiments described herein; and 
           [0026]      FIG. 13  illustrates a screenshot of a navigation display with a range marker and gas stations according to one or more embodiments described herein. 
       
    
    
     DETAILED DESCRIPTION 
       [0027]    Apparatus, systems and methods that implement the embodiments of the various features of the present invention will now be described with reference to the drawings. The drawings and the associated descriptions are provided to illustrate some embodiments of the present invention and not to limit the scope of the present invention. Throughout the drawings, reference numbers are re-used to indicate correspondence between referenced elements. 
         [0028]    Turning to  FIG. 1 , an integrated navigation system within a vehicle is shown. Here, a vehicle interior  100  is depicted to include an integrated navigation unit  105  with a display portion  150  located at a central console area adjacent to the instrumentation gauges  110  and the steering wheel  120  and beneath the windshield  130 . The navigation unit  105  may be controlled by a driver by using any of a plurality of input systems. For example, the navigation unit  105  may have a touch screen for accepting user input by way of tactile contact or a microphone for accepting user input by way of verbal commands. The integrated navigation unit  105  may also be coupled to or in communication with a vehicle control system via wiring (not shown) and thereby able to obtain information related to the status of the vehicle, including how much fuel is left (e.g., remaining gallons of gas or remaining level of electricity or charge, etc.), the make and model of the car, the estimated fuel efficiency of the car, how many miles the vehicle is estimated to be able to travel prior to running out of fuel or charge based on current fuel levels or charge levels and the like. In one embodiment, the navigation unit  105  may receive information from the vehicle control system and further process the information to display or audibly output the information (and/or derivative information) to the user. For example, the navigation unit  105  may receive information such as a fuel level (e.g., 1 gallon of gas remaining) and estimated vehicle fuel efficiency (e.g., 30 miles per gallon) from the vehicle control system and may calculate a “distance-to-empty” (e.g., by taking the gallon of gas remaining and multiplying it by the estimated fuel efficiency). After calculating the “distance-to-empty,” the navigation unit  105  may display and/or audibly provide this information to the driver. 
         [0029]      FIG. 2  illustrates a vehicle interior  200  without an integrated navigation unit  105 . Here, the navigation unit  205  may be a third-party device attachable (via a suction plate) to a vehicle windshield  230 . As shown, the navigation unit  205  may include a display  250  and may draw power from a power source  240  found in the vehicle. Further, the navigation unit  205  may be connected to a universal serial bus (USB) port  230  in communication with the vehicle control system. As shown, the placement of the navigation unit  205  may be such that a driver may view and/or reach the navigation unit  205 , namely near the steering wheel  220  and the instrument gauges  210 . Similar to the navigation unit  105 , the navigation unit  205  may be controlled by a driver by using any of a plurality of input systems. For example, the navigation unit  205  may have a touch screen for accepting user input by way of tactile contact or a microphone for accepting user input by way of verbal commands. The navigation unit  205  may be coupled to or in communication with a vehicle control system via the USB connection and thereby able to obtain information related to the status of the vehicle, including how much fuel or charge is left (e.g., remaining gallons of gas or remaining level of electricity, etc.), the make and model of the car, estimated fuel efficiency of the car, how many miles the vehicle is estimated to be able to travel prior to running out of fuel based on current fuel levels and the like. For example, the navigation unit  205  may receive information such as a fuel level (e.g., 1 gallon of gas remaining) and estimated vehicle fuel efficiency (e.g., 30 miles per gallon) from the vehicle control system and may calculate a “distance-to-empty” (e.g., by taking the gallon of gas remaining and multiplying it by the estimated fuel efficiency). After calculating the “distance-to-empty,” the navigation unit  205  may display and/or audibly provide this information to the driver. 
         [0030]    Regardless of whether the navigation units  105  and  205  or any other navigation unit is utilized, the navigation unit (e.g., navigation unit  105  or  205 ) may further determine a range marker based on the “distance-to-empty” and may display the range marker on the navigation unit. Additionally, the navigation unit may display nearby refueling stations in relationship to the range marker. 
         [0031]      FIG. 3  illustrates an example of a screenshot of a navigation unit display  300  (e.g., display  150  or  250  of navigation unit  105  or  205 , respectively) with a range marker  305 . As shown, the range marker  305  may include a center “target”  310 . The target  310  may be the current location of the vehicle, shown substantially at the center of the range marker  305 . In this example, the range marker  305  may have a radius equivalent to roughly 500 meters based on the scale shown at the upper left hand corner of the display (e.g., showing the distance for 200 meters). In other words, the range marker  305  indicates that the vehicle has enough gas remaining to travel 500 meters and which gas stations may be reachable before the gas runs out (i.e., gas stations within 500 meters). Gas stations  320  are shown inside the perimeter of the range marker  305  and are estimated to be reachable by the vehicle before the gas is exhausted, whereas gas stations  330  are outside the perimeter of the range marker  305  and are estimated to be unreachable by the vehicle before the gas is exhausted. By quickly glancing at the navigation display  300 , a driver may easily ascertain an appropriate gas station, the location of the vehicle in relationship to the gas station and the direction of the gas station. Equally important, the driver may ascertain which gas stations may be outside the range of the vehicle based on the remaining fuel levels thereby avoiding those gas stations. In addition, the navigation display  300  may be configured such that the driver may tap on either of the gas stations marked  320  to obtain turn by turn directions to reach the selected gas station. In one embodiment, the range marker  305  may be formed in the shape of a square, for example, because the roads the vehicle is estimated to travel on are oriented in a square or grid-shaped configuration. 
         [0032]      FIG. 4  illustrates a block diagram of an integrated navigation system (e.g., navigation unit  105  as shown in  FIG. 1 ). As depicted, the navigation unit  400  may be connected to the control system of the vehicle  450 . In one example, the control system of the vehicle  450  includes a Controller Area Network (CAN) bus  445 . The CAN bus  445  is a vehicle bus standard designed to allow microcontrollers and devices to communicate with each other within a vehicle. More particularly, the CAN bus  445  is a multi-master broadcast serial bus standard for connecting electronic control units (ECUs). A modern automobile may have as many as 70 ECUs for various subsystems. For example, ECUs may be used for controlling the turn signals, in addition to other vehicle systems such as the transmission, airbags, antilock braking, cruise control, audio systems, windows, doors, mirror adjustment, etc. Of particular significance, one or more ECUs may provide information such as the fuel remaining, fuel efficiency (e.g., miles per gallon, etc.) and/or distance-to-empty information. 
         [0033]    In this embodiment, the navigation system  400  may be an integrated, OEM navigation system installed at, for example, the front central console area of the vehicle between the driver and the front passenger seat. However, the actual location of the navigation system  400  may be anywhere inside the vehicle. For example, the navigation system  400  may be integrated into the instrument display panel behind the steering wheel or dropped down from the ceiling area of the vehicle. The navigation system  400  may include a processor  405 , an input-output interface  410 , a route-determination unit  415 , a memory  420  and a transceiver  425 . For simplicity, the navigation system  400  may be considered one such ECU connected to the CAN bus  445 , and may communicate with other ECUs via the CAN bus  445 . 
         [0034]    The input-output interface  410  may be, for example, a LCD touch screen input that a user may press to input commands and destination addresses into the navigation system  400 . In one embodiment of the operation of the navigation system  400 , the processor  405  may receive a destination address from the I/O interface  410  and may receive a current location from the transceiver  425  communicating with, for example, a GPS satellite to determine the exact location of the vehicle. Next, the processor  405  may obtain a map from the memory  420  and may provide the current location, the destination and a map to the route calculation unit  415  for determination of the preferred route. Once the route is calculated, the processor  405  may provide the route information to the I/O interface  410  for display and/or verbal output to the driver. As the vehicle moves, the navigation system  400  may track the route and the exact location of the vehicle in order to provide real-time turn-by-turn directions. 
         [0035]    As shown in  FIG. 4 , the processor  405  may be coupled to the CAN bus  445  to communicate with any number of other ECUs, such as a vehicle status information unit  455  or an engine control unit  460 . In one embodiment, electrical control signals generated by the processor  405  may be directly sent to the vehicle status information unit  455  to obtain information such as the remaining fuel in the vehicle, the fuel efficiency of the vehicle and/or the distance-to-empty. Alternatively, the electrical control signals generated by the processor  405  may be sent to a general control unit, such as the engine control unit  460 , which in turn, processes the electrical control signals and provides the requested information or sends a subsequent signal(s) to a different ECU to obtain the requested information. The requested information may be sent to the navigation system  400  via the CAN bus  445 . Once received by the navigation system  400 , the processor  405  may perform calculations (if needed) or may utilize the distance-to-empty information to generate a range marker with a radius equivalent to the distance-to-empty. That is, the range marker may be a circular boundary illustrating the areas that the vehicle may travel before running out of fuel. The navigation system  400  may also obtain refueling station information from the memory  420  and display the refueling stations that are within the circular boundary, thereby informing the driver which stations are within range and may be reachable before the vehicle runs out of fuel. In this manner, the driver may be able to quickly and accurately obtain fuel before running out and being inconvenienced as a result of running out of fuel. 
         [0036]    In one embodiment, after the refueling stations are displayed within the range marker, the driver may select one of the refueling stations, and in response, the processor  405  may obtain new directions from the route-calculation unit  415  and display and/or communicate the new directions as a detour point for the driver. 
         [0037]    Turning to  FIG. 5 , a navigation system  500  as depicted may be connected to a control system  550  of a vehicle. In one example, the control system  550  may include a CAN bus  545 . In this embodiment, the navigation system  500  may be a portable, third-party navigation system usable by the driver inside or outside the vehicle. When utilized to provide turn-by-turn directions for the vehicle, the navigation system  500  may be, in one example, attached to the dash board or the inside of the windshield of the vehicle (e.g., as shown by navigation unit  200  of  FIG. 2 ). The navigation system  500  may include a processor  505 , an input-output interface  510 , a route-determination unit  515 , a memory  520  and a transceiver  525 . The navigation system  500  may further include a port  530  for connecting the navigation system  500  to a port  565  of the control system  550  of the vehicle. The ports  530  and  565  may be, in one example, USB compliant and may be coupled to each other by using a USB cable. For simplicity, the navigation system  500  may be considered by the control system  550  of the vehicle as an ECU when connected to the CAN bus  545  via the USB port  565 , and may communicate with other ECUs via the CAN bus  545 . While the USB cable is described in this particular example, any known connection cable for transmitting and receiving data may be used such as a coaxial cable, a fire wire cable and the like. 
         [0038]    The processor  505 , the input-output interface  510 , the route calculation unit  515 , the memory  520  and the transceiver  525  of the navigation system  500  may operate in a similar fashion as the processor  405 , the input-output interface  410 , the route calculation unit  415 , the memory  420  and the transceiver  425  of the navigation system  400 . The main difference is the inclusion of the port  530  used to interface with the control system  550  of the vehicle. 
         [0039]    Similarly, the CAN bus  545 , the vehicle status information unit  555  and the engine control unit  560  may operate generally like the CAN bus  445 , the vehicle status information unit  455  and the engine control unit  460  as described in correspondence with  FIG. 4 . The main difference is the inclusion of the port  565  used to interface with the navigation system  500 . Notably, by allowing the navigation system  500  to communicate with the control system  550  of the vehicle, functionality is significantly enhanced. For example, older-generation navigation systems may now be retro-fitted for certain vehicles thereby allowing a driver to continue to use an older generation navigation system, which might not have been originally designed to provide such features. 
         [0040]    Turning to  FIG. 6 , a navigation system  600  as depicted may be connected to a control system  650  of a vehicle. In one example, the control system  650  of the vehicle includes a CAN bus  645 . In this embodiment, the navigation system  600  may be a portable, third-party navigation system usable by the driver inside or outside the vehicle. When utilized to provide turn-by-turn directions for the vehicle, the navigation system  600  may be, in one example, attached to the dash board or the inside of the windshield of the vehicle. The navigation system  600  may include a processor  605 , an input-output interface  610 , a route-determination unit  615 , a memory  620  and a transceiver  625 . The navigation system  600  may further include a wireless communication adapter  630  for connecting the navigation system  600  to a wireless communication adapter  670  of a vehicle control system  650 . The adapters  630  and  670  may be, in one example, BLUETOOTH-compliant and may be coupled to each other wirelessly as long as both devices are within communication range. For simplicity, the navigation system  600  may be considered by the vehicle control system  650  as an ECU when connected to the CAN bus  645  wirelessly via BLUETOOTH adapter  670 , and may communicate with other ECUs via the CAN bus  645 . While BLUETOOTH is described in this particular example, any known wireless transmission system for transmitting and receiving data may be used. 
         [0041]    The processor  605 , the input-output interface  610 , the route calculation unit  615 , the memory  620  and the transceiver  625  of the navigation system  600  may operate in a similar fashion as the processor  405 , the input-output interface  410 , the route calculation unit  415 , the memory  420  and the transceiver  425  of the navigation system  400 . The main difference is the inclusion of the wireless communication adapter  630  used to interface with the vehicle control system  650 . 
         [0042]    Similarly, the CAN bus  645 , the vehicle status information unit  655  and the engine control unit  660  may operate generally like the CAN bus  645 , the vehicle status information unit  455  and the engine control unit  460  as described in correspondence with  FIG. 4 . The main difference is the inclusion of the wireless communication adapter  670  used to interface with the navigation system  600 . Notably, by allowing the navigation system  600  to communicate with the vehicle control system  650 , functionality is significantly enhanced. For example, older-generation navigation systems may now be retrofitted for use in certain vehicles, thereby allowing a driver to continue to use an older generation navigation system which might not have been originally designed to provide such features. In addition, where the navigation system and the vehicle control system have both wired and wireless communication systems (e.g., USB and BLUETOOTH capabilities), a redundant system may be achieved and utilized such that the features described herein may be achievable even if one of the connections becomes lost (e.g., the USB cable becomes disconnected). 
         [0043]    Turning to  FIG. 7 , a navigation system  700  as depicted may be configured to connect wirelessly to a physical drive  770 , which in turn, may be connected to a control system  775  of a vehicle. In one example, the physical drive  770  may be a thumb drive or a flash drive. In this embodiment, the navigation system  700  may be a portable, third-party navigation system usable by the driver inside or outside the vehicle. When utilized to provide turn-by-turn directions for the vehicle, the navigation system  700  may be, in one example, attached to the dash board or the inside of the windshield of the vehicle. The navigation system  700  may include a processor  705 , an input-output interface  710 , a route-determination unit  715 , a memory  720  and a transceiver  725 . The navigation system  700  may further include a wireless communication adapter  735  coupled to the processor  705 . In one embodiment, the wireless communication adapter  735  allows the navigation system  700  to communicate wirelessly with a wireless communication adapter  740  of the physical drive  770 . The adapters  735  and  740  may be, in one example, BLUETOOTH-compliant and may be coupled to each other wirelessly as long as both devices are within communication range. In addition to the wireless communication adapter  740 , the physical drive  770  may include a processor  745 , a memory  750  and a wired connection interface port  755 . As shown in  FIG. 7 , a vehicle control system  775  may include a wired connection interface port  780 , a CAN bus  785 , a vehicle status information unit  790  and an engine control unit  795 . The ports  755  and  780  may be, in one example, USB compliant and may be coupled to each other by using a USB cable. 
         [0044]    For simplicity, the navigation system  700  may be viewed by the vehicle control system  775  as an ECU when in wireless communication with the physical drive  770  if the physical drive  770  is connected to the vehicle control system  775 . In one embodiment, the navigation system  700  may communicate with the vehicle control system  775  via the physical drive  770 . In other words, the physical drive  770  may function as a communication medium for transmitting data between the navigation system  700  and the vehicle control system  775 . As discussed above, other communication mediums, both wired and wireless may be substituted for the BLUETOOTH and USB communication systems described. 
         [0045]    The processor  705 , the input-output interface  710 , the route calculation unit  715 , the memory  720  and the transceiver  725  of the navigation system  700  may operate in a similar fashion as the processor  405 , the input-output interface  410 , the route calculation unit  415 , the memory  420  and the transceiver  425  of the navigation system  400 . The main difference is the inclusion of the wireless communication adapter  735  used to interface with the physical drive  770 . 
         [0046]    Similarly, the CAN bus  785 , the vehicle status information unit  790  and the engine control unit  795  may operate generally like the CAN bus  745 , the turn signal control unit  755  and the engine control unit  760 , respectively, as described in correspondence with  FIG. 7 . The main difference is the inclusion of the port  780  used to interface with the physical drive  770 . Notably, by allowing both the navigation system  700  and the vehicle control system  775  to communicate with the physical drive  770 , functionality is significantly enhanced. For example, older-generation navigation systems may now be retro-fitted for certain vehicles thereby allowing a driver to continue to use an older generation navigation system, which might not have been originally designed to provide such features. Moreover, the older generation navigation system does not even need to be able to connect or communicate directly with the vehicle control system. Instead, these seemingly incompatible systems may now interface and communicate with one another via a physical drive such as a thumb drive. 
         [0047]    While the following descriptions will use the navigation system  500  of  FIG. 5  as an example, any of the navigation systems disclosed herein may be configured to perform the methods described. In other words, any of the methods described herein (e.g., as shown in  FIGS. 8-9 ) may be performed by any of the systems described herein (e.g., as shown in  FIGS. 1 ,  2  and  4 - 7 ). 
         [0048]      FIG. 8  is a flowchart illustrating one method of generating a range marker or range ring for a navigation unit. At step  805 , the navigation unit  500  may receive input from the driver or passenger to display nearby gas stations. At step  810 , the navigation unit  500  may request vehicle fuel information from the vehicle system  550 . For example, the navigation unit  500  may request fuel level information, fuel efficiency information and/or distance-to-empty information. Here, at step  810 , the navigation unit  500  may use processor  205  to calculate the distance-to-empty information from the fuel level remaining and the fuel efficiency information or may simply utilize the distance-to-empty information if received from the vehicle system  550 . At step  815 , the processor  205  may calculate the size of the range marker based on the distance-to-empty information. For example, if the distance-to-empty is two miles, that is, the vehicle is estimated to be able to travel two miles before running out of gas, the size of the range marker may be a two mile radius (and scaled accordingly to fit on the navigation map) since the vehicle may theoretically travel two miles in any direction before running out of gas. At step  820 , any gas stations within the range marker (and therefore, reachable by the vehicle before running out of gas) may be retrieved by the memory  520 , which may be configured to store gas station location information. At step  825 , the range marker and gas stations may be displayed on the display portion  150  to the user. Next, the navigation unit  500  determines whether the vehicle has been refueled by requesting fuel level information from the vehicle control system  550 . If so, the range marker and/or gas stations may be removed from the display portion  150  of the navigation unit  500 . Otherwise, the method moves to step  810  again where an updated distance-to-empty may be re-calculated. Until the vehicle is refueled, steps  810 - 825  may be repeated, and accordingly, as the distance-to-empty is reduced, the radius of the range marker may be reduced in a corresponding fashion along with the removal of any gas stations which may no longer be in range. 
         [0049]      FIG. 9  depicts another method of operation of the navigation unit (e.g., navigation unit  500 ). Here, normal operation of the navigation unit is active at step  905 . At step  910 , the navigation unit  500  may receive information from the vehicle control system  550  that a distance-to-empty is below a threshold. The threshold may be, for example, any distance between 0.1 miles-50 miles and may be customizably adjustable by the driver based on when the driver would like to be alerted of low gas. Once the navigation unit  500  receives information from the vehicle control system that the distance-to-empty is below a threshold (e.g., less than 1 gallon of gas left or 5 miles to empty), a range ring mode may be activated in step  915 . At step  920 , the navigation unit  500  may continually adjust in real-time the range ring and the gas stations within range based on the distance-to-empty. In the range ring mode, the control system may automatically display the range marker  305  and the gas station icons within the range marker  305  on the map when the distance-to-empty is below the threshold. The performance of step  920  may be similar to steps  810 - 825  of  FIG. 8 . Next, at step  925 , if the gas or fuel is replenished above the threshold or if the ring mode is cancelled by the driver or passenger, the method reverts back to step  905  and a normal navigation mode is activated. Otherwise, step  920  is re-performed and the navigation unit  500  may continually adjust in real-time the range ring and the gas stations within range based on the distance-to-empty. 
         [0050]    In one embodiment, the threshold may be the density of gas stations within the distance-to-empty. For example, the range ring mode may be triggered if only one gas station remains within the radius of the distance-to-empty. That is, when the navigation system detects that the remaining fuel is estimated to allow the vehicle to reach only one gas station before running out, the range ring mode may be activated. Additionally, an audio message may be played to the driver to alert the driver that only one gas station remains in range. Also, the range ring may include two concentric range rings (one slightly larger the other) indicating that only one gas station remains in the range. The driver may be prompted to input a “yes” or “no” to a query offering to divert the driver from his or her original destination to the remaining gas station. 
         [0051]    In another embodiment, when the range ring mode is activated at step  915  of  FIG. 9 , an audible message may be played to the driver and passengers to explain the range ring mode and allow the driver or passengers to set course for a gas station on the screen. 
         [0052]      FIGS. 10-12  illustrate an example of different screenshots that may be related to the operation of the navigation system as described in  FIGS. 8 and 9 .  FIG. 10  illustrates a navigation display  1000  with range ring  1010 . Here, the range ring  1010  has a radius of 3 miles since the distance-to-empty information as shown in box  1020  is 3 miles. The current location of the vehicle  1030  is shown in relationship to the reachable gas stations  1040 , which are 2.7 miles and 2.2 miles away, respectively. In this figure, no gas stations outside the range ring  1010  are shown even if they exist since they are outside the reach of the vehicle. The distance to each gas station is also shown adjacent to the gas station icon. This allows the driver to determine which gas station is the closest to the current position of the vehicle. 
         [0053]      FIG. 11  illustrates a navigation display  1100  with range ring  1110 .  FIG. 11  may depict a continuation of the situation shown in  FIG. 10 . Here, the range ring  1010  has been reduced from a radius of 3 miles to a radius of 1.5 miles since the vehicle has traveled an additional 1.5 miles. More particularly, as compared to  FIG. 10 , the size of the range ring  1110  has been reduced and one of the gas stations shown in  FIG. 10  is now out of range and removed. The distance to the remaining gas station has also been updated (e.g., from 2.7 miles to 1.2 miles). 
         [0054]      FIG. 12  illustrates a navigation display  1200  with range ring  1210 .  FIG. 12  may depict a continuation of the situations shown in  FIGS. 10 and 11 . Here, the range ring  1210  has been reduced from a radius of 3 miles (as shown in  FIG. 10 ) to a radius of 0.3 miles since the vehicle has traveled an additional 2.7 miles. More particularly, as compared to  FIGS. 10 and 11 , the size of the range ring  1210  has been further reduced and the distance to the remaining gas station has also been updated (e.g., from 2.7 miles to 0.0 miles) as the vehicle has arrived at the gas station. 
         [0055]      FIG. 13  depicts an alternative embodiment of the operation of the navigation system as described in  FIGS. 8 and 9 .  FIG. 10  illustrates a navigation display  1300  with the range ring  1310 . Here, the range ring  1310  has a radius of 3 miles since the distance-to-empty information as shown in box  1320  is 3 miles. The current location of the vehicle  1330  is shown in relationship to the reachable gas stations  1340 . In this figure, only the area inside the range ring  1360  is visible, while the area outside the range ring  1350  is blacked out or otherwise left blank to further alert the driver that the vehicle is low on gas and serves as an additional visual alert that the driver is advised to drive the vehicle to a within-range gas station  1340  for refueling the vehicle. 
         [0056]    In another embodiment, non-circular range markers may be used (not shown). Under this example, the range marker may be overlayed only on drivable roads since a circular range marker may include certain areas (e.g., grass, body of water, etc.) that might not be traversable by a traditional land vehicle. Accordingly, the result of the range marker may not be a circular ring. 
         [0057]    In yet another embodiment, if no gas stations are found within the range marker or if the last remaining gas stations within the range marker are no longer within range (e.g., due to the driver using up additional gas because of mis-turns or if the estimate of the gas remaining is inaccurate), the navigation system (e.g., navigation unit  500 ) may send a signal to the vehicle control system (e.g., vehicle control system  550 ) to automatically send out a SOS signal or otherwise call a vehicle concierge system (e.g., OnStar, LexusLink, etc.) to request customer representative assistance. In this manner, the customer representative may arrange a tow truck or other service representative to bring the vehicle gas before the vehicle runs out of gas or shortly after, thereby cutting down on the time it would normally take for a customer to receive gas. Normally, the customer would only call for help and arrange for the delivery of gas after the vehicle has run completely out of gas. 
         [0058]    While the disclosure primarily uses gas stations as an example, other fueling stations such as electricity depots for electric cars and the like are within the scope of the invention. 
         [0059]    Those of ordinary skill would appreciate that the various illustrative logical blocks, modules, and algorithm steps described in connection with the examples disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. Furthermore, the present invention can also be embodied on a machine readable medium causing a processor or computer to perform or execute certain functions. 
         [0060]    To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the disclosed apparatus and methods. 
         [0061]    The various illustrative logical blocks, units, modules, and circuits described in connection with the examples disclosed herein may be implemented or performed with a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. 
         [0062]    The steps of a method or algorithm described in connection with the examples disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. The steps of the method or algorithm may also be performed in an alternate order from those provided in the examples. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. The processor and the storage medium may reside in an Application Specific Integrated Circuit (ASIC). The ASIC may reside in a wireless modem. In the alternative, the processor and the storage medium may reside as discrete components in the wireless modem. 
         [0063]    The previous description of the disclosed examples is provided to enable any person of ordinary skill in the art to make or use the disclosed methods and apparatus. Various modifications to these examples will be readily apparent to those skilled in the art, and the principles defined herein may be applied to other examples without departing from the spirit or scope of the disclosed method and apparatus. The described embodiments are to be considered in all respects only as illustrative and not restrictive and the scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.