fig1 illustrates the destination tracking system in accordance with the invention with its two essential assemblies . the destination tracking system can be installed in a vehicle operating as a mobile unit . in fig1 the inputs of an electronic control device , or electronic unit , designated as a whole with reference number 2 are connected to the sensors , or signaling devices , mentioned below . a navigational gps ( global positioning system ) receiver 4 produces data which give the geographical position of the control device 2 of the mobile unit by , for instance , geographical latitude and longitude . optionally , the altitude can also be given . a compass 6 containing , for example , two cross coils reads the geomagnetic field . the compass , which is compensated with regard to any magnetic declination due to the control device 2 or the vehicle , produces a signal ∝ which corresponds to the direction of the mobile unit or the vehicle relative to the magnetic north . the compass 6 can be supplemented or replaced by a gyroscope which delivers a more exact value of the direction because of its gyro - stabilization . a mileometer 8 generates an impulse for each unit of distance covered . this can be done , for example , by reading the revolutions of the vehicle &# 39 ; s wheels . unit 10 is a clock which generates a signal corresponding to the absolute time . a vehicle signal generator 12 generates a signal specific to each vehicle type . this device is permanently programmed upon installation in the vehicle . an event manager 14 generates a specific signal corresponding to the occurrence of a specific event : i . e . opening and / or closing a door ; refueling ( opening the petrol tank cap , changing the fuel level ); vehicle maintenance ( resetting the maintenance interval monitoring device ); rain ( continuous use of the wipers ); frost ( low outside temperature ); etc . it is understood that additional signaling devices can be made available to record , for instance , fine weather ( sunshine ), the load under which the engine runs , the weight of the vehicle , the axle loads , etc . in particular , measuring the axle loading is a very simple but most effective method for calculating the stress on the road surface at a road cross section by summing the axle crossings or the normalized axle crossings . the data , when made available to a central computer , can be evaluated to determine the point in time when the road surface requires renewal . the control device 2 also contains an interface 20 to convert the output signals of devices 4 to 14 into digital signals that are then processed within device 2 ; a micro processor 22 executing several different computational procedures ; a rom 24 , which , among other things , contains the working programs for the micro processor 22 ; and a ram 26 with direct access into which the information and current data required to execute the programs are written and from which said information is read out . an input unit 28 is provided to feed the control device 2 with data . an output or display unit 30 can output information acoustically and / or optically . a data input / output device 32 is provided so that the control device 2 can transmit data to and receive data from a remote central computer . the data input - output device 32 can send or receive data directly or by modem . it can also contain a portable data carrier , by means of which data can be read or written into another location , for example by means of a personal computer ( pc ). data can also be inputted and outputted via sensors built into the mobile units and communicating with stationary sensor devices located , for example , in parking lots , petrol stations , etc ., said sensors operating either ultrasonically , in the infrared spectrum , or any other non - contact or wireless method . the data which is derived from signals generated by the devices 4 to 14 are evaluated and stored in a trip storage unit or motion storage unit 40 , respectively , a section data storage unit 42 , a section data file storage unit 44 , a short - term storage unit 46 and an event storage unit 48 . the function and the contents of the storage units named above are explained in detail below . the storage units named above are connected by a data bus 50 . the construction of these units is well known and does not need to be further described here . fig2 shows the circuit diagram of the central computer 62 , which has many components which are similar to those of the control device 2 with which it communicates directly or indirectly over a transmission device 64 . in the total system , several central computers connected in a network can be assigned different tasks . the central computer 62 contains a microprocessor 66 with a rom 68 , and a ram 70 , an overall route file storage unit 72 , a short - term storage unit 74 , and an event storage unit 76 . an input / output device 78 transmits data to and from the central computer 62 . the construction of all of these constituent units , connected over a data bus 80 , is well known . a typical working sequence of the devices described above is outlined below : when a vehicle representing a mobile unit and equipped with the system corresponding to fig1 activated via input unit 28 , is started , the gps receiver 4 sends a signal which identifies the location of the vehicle , compass 6 sends a direction signal ∝, and clock 10 sends a time signal t . these three signals are combined , in the trip storage unit 40 , to a first traveled distance data p i comprising the geographical coordinates x i , y i of the starting point p i and the absolute time t i . the subsequent points p i + 1 , . . . , p i + n are stored in the same manner according to a prescribed routine , for example , after a given time interval given by the clock 10 or after a certain distance has been covered as given by the mileometer 8 . the location coordinates x and y are compared for plausibility with the subsequent points calculated on the basis of the direction signal ∝ and the time signal t , and any deviations are averaged . thus the route covered is recorded by a series of points . the point records can be supplemented by data generated by the vehicle type signal unit 12 , said data way include vehicle model and type , motorization , or similar information mentioned above . if the event generator 14 produces a signal , e . g . a refueling signal , this signal is stored as an event signal e , in the event storage unit 48 together with the location x i , y i and the time t i . if the vehicle is not moving and this stationary period matches an event such as opening and / or closing a door , refueling , etc ., then this is judged to be an interruption of the trip . the points of a first route ending before the event and of the further route traveled subsequent to the event are stored in the trip storage unit 40 . after completion of a trip or even during the trip , section data are generated from the traveled distance or route data stored in the trip storage unit 40 , compressing the traveled distance data by dropping individual points p i and choosing those points p j and p k which are most by dropping individual points p i and choosing those points p j and p k which are most characteristic in defining a section of the route . for example , characteristic route nodes p j and p k are nodes where the vehicle direction ∝ i changes by more than a given predetermined value , or nodes at the intersection of sections oriented in different directions , or nodes that are otherwise conspicuous . the sections p j p k calculated from the route nodes p i stored in the trip store are saved in the section data storage unit 42 in the following manner : p j p k = x j , y j , x k , y k , t jk , and t jk , where x and y represent the geographical coordinates , t jk is the time required to move between the points j and k and t jk is the absolute time of the trip along the section p j p k . thus a large number of section data p j p k are saved in the section data storage unit 42 , said section data being compacted in comparison to the total number of nodes p i passed on the trip since at least some of the sections include more than two nodes p i . the numerous trips carried out by a vehicle , whereby the same section is normally traveled several times , are further compressed in the section data file storage unit 44 . in the section data file storage unit , the absolute time is divided into a number of fields a i relating to specific traffic conditions . each a i stands for a specific time period , for instance , a particular day in a given month , i . e . it defines a traffic relevant time period . traffic relevant time periods are , for example , periods when particularly strong rush - hour traffic occurs every monday morning or , in states which celebrate christmas from december 24th to 26th , periods when especially heavy long distance holiday traffic occurs each year on december 27th on certain routes . the thursday before easter is an example of a holiday not connected to a fixed date which is linked to special traffic conditions . based on the durations t jk and the absolute times t jk , during which certain sections p j p k are traveled , a check routine of the microprocessor 22 can independently determine characteristic periodicities or events and define corresponding traffic relevant time periods a i . the sections p j p k with the corresponding durations t jk and the frequency distribution h ( t jk ) are saved in the section data file storage unit . thus the section data file storage unit contains a section data file which in turn contains the expected time t jk required to traverse a section p j p k grouped by traffic relevant time periods a i . the more section data are assigned to a traffic relevant time period in the section data file storage unit , the more significant is the expected trip time in normal traffic conditions . this precision seems useless if a sudden event changes the traversability of a section p j p k . in order to take into account such special cases , the section data from the section data storage unit 42 are stored in the short - term storage unit 46 for a short period of time , for example the last 24 hours . the events e i reported by the event generator 14 are saved in the event storage unit 48 together with the coordinates x i , y i , and the point in time t i at which the event occurred . in this way , all trips carried out by the respective vehicle are saved in the control device 2 in the form of sections together with the associated trip time and the traffic relevant points in time . it is self evident that the geometric data of the sections , in so far as they are not new , are not re - recorded on each trip . thus usually only the duration of the trip and the absolute time and / or the traffic relevant point in time are registered . the user can , of course , switch off the recording and / or transmission of data at any time . in order to merge the trips of a large number of vehicles and thus achieve an even more significant and extensive coverage of data , the data saved in the storage units 44 , 46 , and 48 of the specific control device 2 of the vehicle are transmitted , either automatically after a given period , or on request by entry in the unit 28 , by the data input / output device 32 to the central computer 62 . this data transmission can be either a wireless transmission from the vehicle , by cable using a data carrier taken from the vehicle , or in any other way . thus it can take place during the trip , or when the vehicle stops , i . e . in a car park , garage , filling station etc . data transmission can be triggered automatically after a given period , or coverage of a certain distance , depending on the update value of the data , or on request from a central computer , or in some other way . the data from different vehicles is merged in the section data file storage unit 72 , the short - term storage unit 74 , and the event storage unit 76 and saved , if required , in accordance with the specific vehicle class ( vehicle signal generator 12 ). if , on data transmission to the central computer 62 , additional vehicle identification data ( vehicle signal generator 12 ) is delivered , the central computer 62 can evaluate the information content and / or the update value of the transmitted data and transfer a corresponding credit note to the sending vehicle . alternatively , a toll account can also be carried out by the central computer . ensuring that the one ( or more ) central computer ( s ) of the system have continuous full coverage of relevant data is achieved as follows : the computer of every vehicle recognizes the update value of the data which it has just determined with regard to the geometric contents ( traveled distances ) and time contents ( trip times ). this update value ( e . g . the amount of new data ) is offered to the central computer together with a geographical specification ( e . g . the geographic center ). if the central computer requests the data , then a credit note is promised if the data is sent immediately . a central computer makes a direct inquiry to vehicles currently in areas for which a data requirement exist . a central computer knows the locations of the vehicles because of their past requests for data or data transmission . a central computer can alternatively request vehicles in the area of interest directly by sending the geometric data of the target area . the vehicles then compare the transmitted data with their own location data . a continuously updated file , more or less condensed , depending on the evaluation procedure , is built up in the central computer 62 , and represents the complete traffic activity within the area covered . this information can be evaluated for highly specific tasks by planning authorities , maintenance authorities , etc . since the data is very comprehensive and up to date it can be used for problems such as green wave traffic signals , one - way traffic , etc . the control of green wave traffic systems require a detailed knowledge of the location of traffic lights , signal time plans , and of the relevant traffic flows . all of this information is contained in merged data received from individual vehicles . given knowledge of traffic light location and time phases , the individual vehicle can receive a recommendation on speed so that the probability of a stop free journey is maximized . the entire system requires no infrastructure such as signal coils in the streets , central storage of the road network for example in cd - rom , collection of traffic statistics , etc ., although the use of a cd - rom as an initial data set is not excluded . the above description deals with the system as far as it is used to generate data via signaling units 4 to 14 contained in individual vehicles ( see fig1 ), which data can be used for a destination tracking system . the following description explains the use of the system for deriving tracking data from the generated data . it is assumed that the driver of a vehicle wants to make a trip from a location a to b on a third monday morning in september , the route leading mostly through rural areas . the desired trip is entered into the input unit 28 by reading , for instance , a visiting card containing the origin node a and a further visiting card containing the destination node b , both visiting cards containing the geographical information in the form of bar - codes . it is understood that a numeric input or a voice input of the locations of origin and destination are possible alternatives . it is advantageous to enter the origin and / or destination node by means of coordinates since this also permits to enter destinations for which either a postal code or similar address is not available or not known to the system . a further advantage in addressing destinations by coordinates is that the system is able to direct the user to the closest identifiable point , if a desired destination entered is not identifiable . since the intended trip is a route which the vehicle does not usually utilize , it is probable that no relevant information is available in the storage units 40 to 48 . thus the input unit 28 will request a central computer for relevant data for the desired trip , e . g . entering the desired trip into the central computer 62 which either calculates a route and sends back the resulting route data set , or just sends all relevant data concerning the areas of origin and destination to the control device 2 which will calculate the route . in both cases the data transmission is charged to the requesting vehicle by the central computer 62 . this means that the request is only answered if specific vehicle data or a code identifying either the individual vehicle or the driver has been entered . the full route is put together from the individual section p j p k by using a well known optimization algorithm operating on the basis of the data in the section data file 72 or the updated section data file 44 in such a way that , in the case where the trip takes place mostly in rural areas , the distance traveled is minimized . if the trip is mainly through municipal areas or , on express request by the driver , an optimization algorithm which minimizes the total duration of travel time can be chosen . other possible optimization criteria can be given , i . e . avoidance of road tolls or mountain passes , or minimization of fuel consumption , etc . the recommended individual route sections are compared with the section data already stored in the short - term storage units 46 or 74 . the data of the short - term storage units may suggest that the travel time expected under normal traffic conditions or normal state cannot be realized on a recommended route section . the display unit 30 shows the trip route made up of the individual sections together with the expected duration or arrival time . as the route is traveled the individual sections are identified so that route tips can be given continuously and the location of the vehicle can be shown on a map . deviations between the route actually driven and the planned route can be corrected by the computer in the vehicle by calculating and displaying an updated route recommendation . in addition , the event storage unit 48 can be used if , for instance , it is necessary to refuel by requesting the location of a petrol station in the relevant area . alternatively , referral to an open petrol station can be automatic and navigational help to find the station can be given . as demonstrated above , the invention creates a system using modern sensor , computer , and storage technology to enable the optimal use of the available highway or route network , respectively , and to achieve predictable travel times , even in high traffic densities , by optimizing the route . the procedure for updating and merging data corresponding to the invention &# 39 ; s method is described below with reference to fig3 to 10 . fig3 shows a known route or road geometry in which the nodes 1 to 16 represent road intersections and the links between these nodes represent roads . this known road geometry can be stored either in the overall route file storage unit 72 of the central computer 62 and / or in the section data file storage units 44 installed in the mobile units or vehicles . on the basis of this known route geometry or traversable road network , various cases will be described below . in the first case , referring to fig4 and based on the given route geometry shown in fig3 it is assumed that a first mobile unit , a motor vehicle for example , wishes to drive from the origin s , which lies at node 1 , to a destination node z which lies on node 16 of the given route geometry . thus both the origin s and the destination z are known . the central computer 62 or the optional data processing unit or microprocessor of the mobile unit recommend a route calculated on the basis of the existing data material , i . e . the road geometry according to fig3 taking into account travel times from a possible earlier trip of the same mobile unit or that of another mobile unit between the nodes s and z . the recommended route s → 2 → 6 → 7 → 8 → 12 → z is represented by “ x ” in fig4 . during the trip microprocessor 22 checks whether the mobile unit is moving along the recommended route . it does so by using sensor 4 to determine the location ( i . e . gps receiver 4 in fig1 ) and sensor 6 to determine the direction of motion of the mobile unit ( i . e . compass 6 in fig1 ). since the route is known it is not recorded again . on the other hand , however , the travel time , i . e . the time of motion , of the first mobile unit is recorded . the pure travel time , i . e . the time of motion of the mobile unit , and the total travel time , i . e . the difference between departure time of the mobile unit at the origin s and arrival time at the destination z , can vary due to stops at traffic lights , building works , etc . the distinction between the condition “ motion of the mobile unit ” and the condition “ mobile unit is stationary ” can be determined , for example , by means of an appropriate sensor , attached to a wheel or a shaft of the mobile unit , to measure or count rotations . if an additional sensor is provided to measure the fill state of the fuel tank of the mobile unit , the state “ mobile unit is stationary while purchasing fuel ” can be recorded and used when determining the total travel time . it is also possible to record the location of a petrol station , if this is not yet known , and transmit this information to the central computer 62 , along with the rest of the data transmitted by the mobile unit so that this location information can be made available to other mobile units on the same route or in the same area . upon reaching the destination z or after a predetermined time period , the transmission device , i . e . the data input / output unit 32 in fig1 transmits the data recorded by the first mobile unit during motion from the intermediate storage units 44 , 46 and 48 . this can be the pure travel time , the total travel time , the start time of the mobile unit , the weekday , the location of a petrol station , etc . if the first mobile unit is provided with the optional cpu 22 , then this data can be processed before being transmitted . data is received by the central computer 62 over its transceiver device , i . e . the transceiver unit 64 in fig2 and processed and evaluated by the cpu 66 of a central computer before being saved in the overall route file storage unit 72 in accordance with the route taken between the origin s and the destination z , the weekday and start time as well as being scored with the pure travel time and / or the total travel time . insofar as trip times for alternative routes from the origin s to the destination z in fig4 are not yet known , if another mobile unit wishes to travel along the same route or has the same origin node and destination node , the central computer 62 or the cpu 22 of the mobile unit will , upon transmission of said available data by the central computer 62 to the cpu 22 of said mobile unit , will recommend the route s → 2 → 6 → 7 → 8 → 12 → z , since this route is the only one which has been recorded earlier with a realized trip time . the case can now be considered where a second mobile unit , or the first mobile unit described above , makes the same trip between the origin node s and the destination node z in fig4 . however , in this case , the mobile unit needs to travel over node 9 ( for example because the driver of this mobile unit has to take care of some task on the road section between points 5 and 9 or between points 9 and 10 ). in such case it is possible to enter this constraint together with the input of the destination . the central computer 62 or the optional cpu 22 of the mobile unit takes into account the constraint and recommends the route s → 5 → 9 → 10 → 11 → 15 → z . this route is marked with “ o ” in fig4 . the absolute starting time of the trip of the mobile unit is again determined and saved . once again the pure travel time along each section is recorded together with the total travel time . since the recommended route is a component of the known road geometry , no recording of road geometry is carried out . only the location and the direction of motion are checked by the corresponding sensors 4 and 6 to ensure that the mobile unit actually moves along the suggested route . recorded data is sent by the transmission device 32 to the central computer 62 at the end of the journey or after a predetermined time period . the central computer stores the transmitted data as outlined previously and scores it with the pure travel time and / or total travel time . with regard to the evaluation criterion “ shortest travel time ”, the individual routes are immediately comparable provided that the journey of the second mobile unit has been executed at the same time of day , and on the same weekday , as that of the first mobile unit . assume that the route s → 2 → 6 → 7 → 8 → 12 → z has a shorter travel time (“ pure ” travel time or total travel time ) than the route s → 5 →→ 9 → 10 → 11 → 15 → z , perhaps because the traffic light switching of the second route mentioned is more unfavorable or because the volume of traffic is higher on this route than on the first one . in such case , either the central computer 62 takes into account this result to send the assumed travel time for a recommended route to a mobile unit or it sends the evaluated result to the cpu 22 of the mobile unit , which can then take into account the information independently . thus a mobile unit making the trip from the origin node s to the destination node z in fig4 on a specific weekday at a specific time of day , on the basis of this evaluated result , can drive along the route with the minimum time . it is self evident that on repeating this procedure with a large number of mobile units within the framework of the road geometry , as shown in fig3 favorable routes for other times of day and weekdays can be determined . it should be noted , in this context , that the storage of routes together with the trip times could be done by storing the route as a whole or by storing the individual route segments and their corresponding realized travel times . a substantially higher storage capacity is needed for the last - mentioned method , but a far greater flexibility is reached since a disturbance prolonging the travel time within a route does not require the recalculation of a complete route but possibly only the recalculation of the one segment which needs to be replaced . this case is explained below in detail . in determining an optimal route with respect to travel time , the situation can arise where a particular route is favorable on a specific weekday at a specific time of day , but unfavorable at another time of day and / or weekday . furthermore , it is self - evident that the significance and reliability of route recommendations increase with the number of trips made by mobile units in the road network depicted by fig3 . thus , for a time - optimal route between the origin s and the destination z , highly differentiated route recommendations may be made for different times of the day and days of the week . changes to the road geometry can also be taken into account . for example , suppose that road work is commenced on the route s → 2 → 6 → 7 → 8 → 12 → z between the points 6 and 7 which results in traffic congestion . the method in accordance with the invention takes into account this event by recording an increase in the travel time on the route . said increase in travel time would be transmitted to the central computer at the end of the trip . after a certain total number of measured travel times , said number of samples being freely selectable as a function of the desired stability of the result , the route would be newly evaluated by the central computer 62 . thus , in recommending a route , the new evaluation would be taken into consideration by the central computer 62 or an optional cpu 22 of a mobile unit , either by calculating a completely new route ( e . g . the route s → 5 → 9 → 10 → 11 → 15 → z ), or by making a modification to the first route recommendation so that the route would now run : s → 2 → 6 → 10 → 11 → 2 → z . the destination tracking system or method in accordance with the invention is not only able to determine a minimal time route from several possible routes , depending on the time of day , day of week , etc ., for a given road geometry and to update the route recommendations continuously but also to update the road geometry . this capability is explained below . it is assumed that a third mobile unit also wants to travel from the origin s to the destination z , with the road geometry of fig3 and fig4 being known . the mobile unit , however , actually takes the route s → 6 → 11 → z , shown in fig4 by the dotted line , due to the knowledge of the user . during this trip , the new road geometry will be recorded by the mobile unit , in particular by means of sensors 4 and 6 which detect the position and the direction of motion of the mobile unit , and this information will then be transmitted to the central computer 62 at the end of the journey or after a predetermined time period . the central computer 62 can now update its data stock with regard to the road geometry and also inform the cpu 22 of the mobile units . in recording this , until now , unknown route , the travel time is also recorded so that this route or its individual segments can be evaluated with regard to the travel time and possibly recommended as a time optimal route . a further case corresponding to fig5 is examined below . it is assumed that a mobile unit moves from the origin node s , which corresponds to node 1 , to a destination node z outside the known road geometry and thus unknown to the navigational system . on the basis of the given road geometry , the central computer 62 or the optional cpu 22 of the mobile unit is unable to find a route to a node z outside the known road geometry . however , upon entry of the coordinates of said destination node z , the central computer 62 or the optional cpu 22 can identify node 16 as the point nearest to the unknown node z . thus a route recommendation is made which brings the mobile unit to a node directly in the neighborhood of the node z . this route might be s → 6 → 11 → 16 . this is possible as the new route found in connection with the case depicted in fig4 is now known after merging the data representing the corresponding road geometry . the mobile unit must now drive independently from node 16 to the destination z . this new path from node 16 to destination z is recorded and at least the new section is sent to the central computer 62 at the end of the trip or after a predetermined period of time . the central computer thus expands its data set . fig6 shows the road geometry known after such trip . the newly introduced node is labeled as 17 . even though the user of the mobile unit would have to find the link or destination node without the aid of the system according to the invention , the system will , with a high degree of probability , be able to lead the mobile unit back , e . g . to the starting point , due to the recording of the road geometry . fig7 depicts a case analogous to the previous case , but where the destination node z is known while the origin node s is unknown . the mobile unit commences its trip , at first without a recommended route , until it reaches a node that is known to the central computer 62 or its optional cpu 22 . in the present case this is the node 2 . it could just as well have been any other node such as 1 , 3 , 4 , 5 or 9 , etc . the route from the origin node s to the point 2 is recorded together with the travel time . on reaching node 2 , the central computer 62 or the optional cpu 22 of the mobile unit is now able to recommend a route based on the current updated database after merging the data resulting from the examples in fig5 and fig6 . this route could be the route 2 → 3 → 7 → 11 → 16 → z . however , since the driver of the mobile unit knows that a direct geometric connection exists between nodes 2 and 7 , he can take advantage of such knowledge when driving to node 7 . the mobile unit records this new link in addition to the section already traversed by the mobile unit between the origin node s and node 2 . the mobile unit then turns off the recording of road geometry after reaching node 7 since it is traversing known route sections . however , determining and recording of travel times and / or of the absolute times to reach a node are continued . the newly recorded road sections are transmitted to the central computer 62 either at the end of the trip or after a predetermined time period . the central computer evaluates the sections as to the trip times and stores them . the new road intersection is labeled as 18 in fig8 which now reflects the new known road geometry . this updated road geometry can now be provided to all mobile units either automatically or on demand . a final case is shown in fig9 . the location of the origin node s and the destination node z are known . however , on his way to the destination node z ( i . e . node 17 ), the driver of the mobile unit wishes to visit node 19 which lies outside the known road geometry . since the connection between the origin node s ( node 18 ) and node 2 is known to the central computer 62 or the optional cpu 22 of the mobile unit from the case described with reference to fig7 and fig8 and , due to the entry of the coordinates of destination node 19 , the system components 62 and / or 22 also know that node 13 of the known road geometry is the point closest to node 19 , and the recommended route might be s -& gt ; 2 -& gt ; 6 -& gt ; 10 -& gt ; 9 -& gt ; 13 . the driver must find his own route from node 13 to node 19 and back to node 13 or look for a new route , possibly over node 14 , or a direct route to the destination node z . it is assumed that the driver of the mobile unit is looking for a direct route to the destination node z and it is also assumed that a direct route between the origin node s ( node 18 ) and node 1 is known to the driver of the mobile unit . the route between the origin node s and node 1 , between node 13 and node 19 , as well as between nodes 19 and z is recorded by the mobile unit and transmitted to the central computer 62 as described above . the transmitted data is evaluated as before and made available to the mobile units . fig1 represents the now known road geometry obtained by merging the data . in contrast to known destination tracking methods or systems , the method or system according to the invention continuously revises data with respect to the traversable network sections as well as realized and realizable trip times or times of motion , to calculate minimal time routes between two arbitrary nodes . this is achieved by merging new data on links and traffic conditions that model reality into the system &# 39 ; s storage units . furthermore , the system or method according to the invention , being based on the use of coordinates , can lead a mobile unit to a node close to the desired location even when this location is not accessible on the basis of the road geometry known to the system . in conclusion , it is taken for granted that the term “ mobile unit ” can apply to any type of vehicle as well as to pedestrians who are equipped with a portable appliance which exhibits the same constructional features as those discussed above .