Abstract:
A pedometer for determining the length of a route traveled on foot includes an acceleration sensor for ascertaining a number of steps as well as a pressure sensor for ascertaining a change in geographic elevation, and an evaluation unit being configured to adapt the step length to the measured average elevation change per step.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a pedometer. 
     BACKGROUND INFORMATION 
     Pedometers of this kind, hereinafter also called “step counters,” are commonly known. The document DE 10 2007 043 490, for example, discloses a pedometer in which a number of steps, and by way of a predefined step length a route traveled, can be deduced by evaluating the signals of an acceleration sensor. Because the distance thereby ascertained corresponds only to a “bee-line,” projected onto the plane, between the starting point and destination, provision is further made to use a pressure sensor to take into account the elevation profile over the route segment. A disadvantage of the conventional pedometer is that provision is made only for general consideration of how the elevation that has been negotiated influences the length of the route traveled. The existing art does not disclose variable adaptation to a change in elevation of the step length taken into account in route measurement, and this form of route calculation is therefore relatively inaccurate. 
     SUMMARY 
     The pedometer according to example embodiments of the present invention, and the method according to example embodiments of the present invention for counting steps, have the advantage, as compared with the existing art, that an adaptation of the predefined step length to the measured average elevation change is performed for each step, i.e. in variable fashion, if the measured average elevation change per step, in particular with reference to a specific sub-route, changes significantly. This enables a more accurate determination of routes traveled on foot on the basis of pedometers. 
     In general, a person varies the length of his or her steps when walking. The step length depends in particular on the elevation being negotiated with each step while walking. For example, a person usually automatically shortens the length of his or her steps when walking outdoors uphill or downhill. The step length becomes considerably shorter especially when climbing or descending stairs. This results in an erroneous calculation of routes traveled on foot if the calculation is based on the number of steps and assumes an unadapted step length. It is advantageous that a relatively flexible adaptation of the step length is possible as a function of the profile of the route traveled. For example, even in the case of a sequence of positive and negative elevation changes that add up to a total elevation change of zero, an adaptation of step lengths to the respective positive or negative slope can be performed. 
     Especially when ascertaining the length of routes traveled in buildings, in which stairs need to be repeatedly climbed and described, a higher accuracy as compared with conventional systems can thereby be achieved. If the calculated routes traveled are to be used, for example, for dead reckoning, it is advantageous, in particular inside buildings, tunnels, and subway stations, to be able to make an accurate determination of routes traveled on the basis of step length, since a position correction based on GPS signals, which is usually performed in the context of dead reckoning, is not possible in locations with poor or insufficient GPS reception. Dead reckoning of this kind may be necessary, for example, for location-based services. 
     According to example embodiments, provision is made that for a measured average elevation change per step of zero, the variable step length has a value corresponding to the predefined step length, which value is referred to hereinafter as a “maximum value”; and that the variable step length becomes increasingly shorter as the absolute value of the measured average elevation change per step becomes greater. This means that on a level route (i.e. no measured average elevation change, or the measured average elevation change per step is equal to zero), the variable step length is allocated to a maximum value. The allocated value of the variable step length decreases as the absolute value of the measured average elevation change per step increases. A particularly accurate route calculation thereby becomes possible. 
     According to example embodiments, provision is made that the predefined step length is in a range from 50 cm to 100 cm, particularly preferably in a range from 60 cm to 80 cm, and very particularly preferably is 70 cm. 
     According to example embodiments, provision is made that the variable step length is zero when the absolute value of the measured average elevation change per step is greater than a predefined upper elevation change per step, the predefined upper elevation change per step being in a range from 25 cm to 35 cm, particularly preferably in a range from 27 cm to 30 cm, and very particularly preferably being 28 cm. This likewise makes it possible to improve the calculation of routes. Because the average height of a stair riser in buildings is approximately 14 cm, a step in which, for example, two stair risers are climbed or descended at once can still be classified as walking on a upward or downward slope. For greater elevation changes per step, on the other hand, a special instance must be assumed, for example climbing or descending a ladder. 
     According to example embodiments, provision is made that the evaluation unit is configured for averaging of the pressure signals over a time interval, the length of the time interval being equal to 1 to 10 seconds, preferably 2 to 6 seconds, and particularly preferably 3 to 4 seconds. This averaging is effected in order to reduce errors when measuring the average elevation change per step, which errors can occur as a result of movements of a user of the pedometer or because of interference with the pressure sensor signal. 
     According to example embodiments, provision is made that in a first region of the measured average elevation per step starting from zero up to a predefined threshold value, the variable step length is the predefined step length, i.e. corresponds to the maximum value; and that in a second region starting from a first threshold step length, the variable step length decreases as the absolute value of the measured average elevation change per step increases, the threshold value being in a range from 4 cm to 12 cm per step, preferably in a range from 6 cm to 10 cm per step, and particularly preferably being 8 cm per step, and the first threshold step length being preferably in a range from 35 cm to 60 cm and particularly preferably in a range from 40 cm to 58 cm. This threshold value is provided in addition to the time averaging of the pressure signal in order to compensate for interference with the signal of the pressure sensor. 
     A further aspect hereof is a method for determining the length of a route traveled on foot, a number of steps being ascertained on the basis of the acceleration signals of an acceleration sensor, and a change in geographic elevation being ascertained on the basis of the pressure signals of a pressure sensor. An adaptation of the step length to the measured average elevation change per step enables a more accurate determination of the length of the route traveled than in conventional arrangements. 
     A further aspect hereof is use of the above-described pedometer for dead reckoning in buildings and for the provision of location-based services. 
     Exemplifying embodiments of the present invention are depicted in the drawings and explained further in the description that follows. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  schematically depicts the pedometer according to an exemplifying embodiment of the present invention, 
         FIG. 2  schematically depicts an example of an elevation profile along a route segment, 
         FIG. 3  schematically depicts the change in variable step length as a function of the elevation change per step, according to a first embodiment of the present invention, 
         FIG. 4  schematically depicts the change in variable step length as a function of the elevation change per step, according to a second embodiment of the present invention, and 
         FIG. 5  schematically depicts the change in variable step length as a function of the elevation change per step, according to a third embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a schematic block diagram of a pedometer  10  according to an exemplifying embodiment of the present invention, pedometer  10  having an acceleration sensor  20 , a pressure sensor  30 , an evaluation unit  40 , and an output unit  50 . 
     The signals of acceleration sensor  20  and of pressure sensor  30  are delivered to evaluation unit  40 , which in turn delivers the results of an evaluation of those signals to output unit  50 . 
       FIG. 2  is a schematic diagram of an example of an elevation profile along a route segment of a route traveled  13 . Route  13  has a first sub-route  11  and a second sub-route  12  that exhibit different slopes. The geographic elevation  14  is additionally indicated. In addition, a variable step length  9 , which is used as the basis for calculating the length of route traveled  13 , is depicted schematically in various regions of route  13 . It is evident that variable step length  9  differs in different regions of route  13 . On first sub-route  11  having a first slope, a comparatively shorter variable step length  9  is assumed. On second sub-route  12  having a greater slope, an even shorter variable step length  9  is assumed. A greater slope (positive or negative) corresponds to a greater measured average elevation change per step  2 . 
     In  FIG. 3 , the values assumed by variable step length  9  in accordance with a first embodiment of the present invention are plotted against the measured average elevation change per step  2 . For a measured average elevation change per step  2  of zero, variable step length  9  is assigned a value of 70 cm, which corresponds to an assumed value for a person&#39;s step length on level ground. This value is decreased, according to the present invention, for measured upward or downward slopes, and this value is therefore referred to hereinafter as a “maximum value.” For a measured average elevation change per step  2  having a greater absolute value, variable step length  9  continuously decreases until, starting from an upper elevation change per step  3 , a variable step length  9  of zero is set. Beyond this upper elevation change per step  3 , it is assumed that special instances exist; these can be, for example climbing or descending a ladder, or changes in environmental influences. Instead of the linear profiles depicted, however, other (for example, step-shaped) profiles are also conceivable, such as those that can result from digitization of the pressure and acceleration signals. 
     In  FIG. 4 , the values assumed by variable step length  9  in accordance with a second embodiment of the invention are plotted against a measured average elevation change per step  2 . For a measured average elevation change per step  2  of zero, variable step length  9  is assigned a value of 70 cm, which corresponds to an assumed value for a person&#39;s step length on level ground. Starting from a threshold value  5  of the measured average elevation change per step  2 , a change in slope is assumed. Variable step length  9  correspondingly decreases to a first threshold step length  7  that corresponds to the measured average elevation change per step  2 . In a second region  6 , variable step length  9  decreases, as described in  FIG. 3 , to the upper elevation change per step  3 , beyond which a variable step length  9  of zero is set. 
     In  FIG. 5 , the values assumed by variable step length  9  in accordance with a third embodiment of the present invention are plotted against a measured average elevation change per step  2 . For a measured average elevation change per step  2  of zero, in a first region  4  the variable step length  9  is assigned a value of 70 cm, which corresponds to an assumed value for a person&#39;s step length on level ground. Starting from a threshold value  5  of the measured average elevation change per step  2 , variable step length  9  decreases to a second threshold step length  8 . This second threshold step length  8  has a constant value, corresponding to a constant step length when climbing or descending stairs, over an entire second region  6 . Region  6  ends at an upper elevation change per step  3 , at which variable step length  9  decreases again to zero.