Abstract:
A navigation system is used to assist a user in proceeding from a current location to a desired destination. The navigation system includes a processor for storing a database of roads and a system for determining the current position of a vehicle in relation to the database. A user can select a desired destination in the database by using an input device which sends the selection to the processor. The navigation system determines a route to the selected destination. An output device displays the route and the vehicle&#39;s current position by automatically scaling the display to include the route and the current position.

Description:
This application claims priority to U.S. Provisional Application Serial No. 60/084,228 filed on May 5, 1998. 
    
    
     BACKGROUND OF THE INVENTION 
     This present invention relates to navigation systems and more particularly to a navigation system with a vehicle location display for showing a vehicle&#39;s current location and the location of the desired route. 
     Navigation systems generally provide a recommended route from a starting point to a desired location. Generally, the starting point and desired location are selected from a large database of roads stored in a mass media storage, such as a CD ROM, which includes the roads in the area to be traveled by the user. The navigation system can be located in a personal computer or it can be installed in a vehicle. If the navigation system is installed in a vehicle, the starting point is typically the current position of the vehicle, which can be entered into the navigation system by an associated position determining system that usually includes a Global Positioning System (GPS) receiver. 
     The navigation system determines a route from the starting point to the destination utilizing an algorithm well-known to those in the art and currently in use in many navigation systems. Usually there are many potential routes between the selected starting point and the desired destination. Typical navigation systems select a recommended route based upon certain predetermined criteria including the length of the route and the estimated time of travel on the route. Depending upon the predetermined algorithm of the navigation system, the navigation system will recommend the route with the shortest total length, the lowest total time, or some weighted average of length and time. 
     The recommended route is then displayed to the user as a map showing the starting point, desired destination and highlighting the recommended route. Preferably, if the navigation system is installed in a vehicle, the navigation system displays the current location of the vehicle and provides turn-by-turn instructions to the driver, guiding the driver to the selected destination along the recommended route. 
     The typical navigation system provides the current vehicle location to the user by displaying either a textual guidance mode screen having a set of instructions and the current location or a guidance mode map showing the starting point, desired destination, current location and highlighting the recommended route. 
     One disadvantage with current displays is that the present location of the vehicle and the starting point of the recommended route may not be able to be seen on the display screen at the same time. This can occur in a situation where the vehicle is moving while the route is being determined and the current position of the vehicle and the nearest point on the recommended route can no longer be in the same screen due to the current display scale. This makes it difficult for the user to proceed to the starting point of the recommended route. Some map displays permit the user to select a viewing scale to aid the driver in showing his current position in relation to the starting point of the recommended route, but this requires further input from the user while the user is en route. Accordingly, it is desirable to provide a vehicle location display that automatically scales the display to show a vehicle&#39;s current location and the starting point of a recommended route on the same screen. 
     SUMMARY OF THE INVENTION 
     In general terms, this invention provides a vehicle location display for a navigation system. The vehicle location display displays the current vehicle location on a display device of a navigation system in a graphical display mode. In the graphical display mode, the display displays a map having the current location of the vehicle. The navigation system includes a database of roads and a system for determining the current position of a vehicle in relation to the database. A user can select a desired destination in the database by using an input device connected to the navigation system. The navigation system also includes a system for determining a route to the destination. A display displays the route and the vehicle&#39;s current position by automatically scaling the display to include the route and the current position. 
     These and other features and advantages of the present invention will become more apparent to those skilled in the art from the following detailed description of the presently preferred embodiment. The drawings that accompany the detailed description can be described as follows. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic of the navigation system of the present invention; 
     FIG. 2 illustrates an example of a display showing a current location; and 
     FIG. 3 illustrates an example of a display showing the present location and a desired route to a predetermined destination. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The navigation system  20  of the present invention is shown schematically in FIG.  1 . The navigation system  20  includes a central processor unit (CPU)  22  connected to a display  24 , such as a high resolution LCD or flat panel display. The CPU  22  is also connected to an input device  26  such as a mouse, keyboard, key pad, or remote device. Alternatively, the display  24  can be a touch screen display. The navigation system  20  further includes a storage device  28 , such as a hard drive  28  or a CD ROM, connected to the CPU  22 . The storage device  28  contains a database including a map of all roads in the area to be traveled by the vehicle  32  and may contain the software for the CPU  22 , including the graphical user interface, route guidance, operating system, position-determining software, etc. 
     The navigation system preferably includes position and motion determining devices, such as a GPS receiver  32 , a gyroscope  36 , a compass  38 , a wheel speed sensor  40 , and an orthogonal multiple axis accelerometer  41  all connected to the CPU (connections not shown for simplicity). Such position and motion determining devices are well known and are commercially available. 
     The navigation system  20  determines the position of the vehicle  32  relative to the database of roads utilizing the position and motion determining devices. The driver selects a destination relative to the database of roads utilizing the user input device  26  and the display  24 . The navigation system  20  then displays turn-by-turn instructions to the driver to guide the driver to the desired destination from the resent position. 
     Often the navigation system  20  is determining or calculating a route while the vehicle  32  is moving. In some situations, the current location of the vehicle  32  may not be near the recommended starting point of the route, such as when the vehicle is in a parking lot, on a new street, or on a small side street that is not included in the database of roads, for example. Alternatively, the recommended starting point of the route may be at a point that the vehicle has already passed. If the vehicle is not on the recommended route when the route calculation is finished, the display  24  displays a map showing the recommended route and the current vehicle position on the map. The display  24  also includes an instruction instructing the driver to proceed to the route. Since the vehicle  32  may have been moving while the route was being calculated, the current position of the vehicle and the nearest point on the recommended route may no longer be in the same screen, depending upon the current display scale, as shown in FIG.  2 . FIG. 2 shows a vehicle&#39;s current position, indicated by the arrow, on a map scale that does not show the starting point of the recommended route. 
     In the present invention, when the route calculation is completed, the display  24  automatically scales the display of the map, as shown in FIG. 3, so that the nearest point on a recommended route and the current position of the vehicle  32  are both shown on the display  24 . FIG. 3 shows the display  24  when the navigation system  20  has automatically scaled the display  24  to simultaneously show the vehicle&#39;s current position and the starting point of the recommended route. The current position of the vehicle is represented by the arrow and the recommended route is shown as highlighted with a thicker line. There is also a current street field  42  which displays the name of the street on which the vehicle is currently positioned. 
     The navigation system  20  also determines a distance from the current position to the nearest point on the recommended route and displays this distance on the display  24  so the driver knows how far he is from the starting point of the route. This distance can be communicated to the driver by either or all of the following ways: by a textual display, by an audible indication, or by a graphical display. For example, the display  24  could have a distance field  44  displaying how far the vehicle  32  is from the recommended route, as shown in FIG.  3 . 
     As previously mentioned, the navigation system  20  is often calculating the route while the vehicle  32  is moving. In this situation, the navigation system  20  first determines the current position of the vehicle with respect to the database of roads. Once the recommended route has been calculated, the navigation system  20  then determines a second position, i.e. the new current position, of the vehicle with respect to the database of roads because the vehicle has changed its location since the first position, i.e. the original current position, was determined. The display is then automatically scaled to show the new current position of the vehicle and the nearest point of the recommended route. Thus, the navigation system  20  is determining the route based on the first or original position of the vehicle when the destination was selected and is automatically scaling the display to show both the nearest point of the recommended route and the second or new current position of the vehicle. The navigation system determines the distance from the second or new current vehicle position to the route and displays this distance in the distance field  44  on the display  24 . 
     As shown in FIG. 3, the first or original position of the vehicle when the destination was selected is shown as a dashed circle while the second or new current position is shown as the arrow. The prior location of the vehicle, shown by the dashed circle is not typically part of the display  24  but is only used to illustrate that the vehicle has changed its location from when the destination was originally selected and when the navigation system  20  has completed calculating the route. 
     If the vehicle is moving when the route is calculated, the display  24  may have to be automatically scaled again after the initial display of the route. If the vehicle is moving away from the route, it may be necessary to zoom out after the initial display of the route in order to maintain the route on the display. Similarly, if the vehicle is moving toward the route after the initial display of the route, the display may zoom in to display the current location of the vehicle and the route. 
     The inventive method for automatically scaling the display  24  for the navigation system  20  includes the following steps: (a) determining a first position relative to a database of roads; (b) selecting a destination in the database; (c) calculating a route to the destination in the database; (d) calculating a map scale including the route and the first position; and (e) displaying the route and the first position based on the map scale. 
     If the recommended route and the first position are not viewable on the display at the same time, a first map scale is displayed prior to step (e) and a second map scale, different from the first map scale, is displayed during step (e). 
     Additionally, if the vehicle  32  is moving when the destination is selected, the method includes the steps of determining a second position relative to the database, the second position being different than the first position, and calculating the map scale based on the second position. The first position is the location of the vehicle when the destination is selected and the second position is the location of the vehicle once the navigation system  20  has determined the route to the desired destination. 
     Also, the method includes the step of determining a distance from the first position to the nearest point on the route when the vehicle is stationary or determining a distance from the second position to the nearest point on the route when the vehicle is moving. This distance is also displayed on the display  24  along with the vehicle&#39;s current position and the nearest point of the recommended route. 
     Preferred embodiments of this invention have been disclosed, however, a worker of ordinary skill in the art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.