The invention concerns an evaluation method for recognition of navigable streets, which are for example toll roads, using values measured in the vehicle such as for example position and direction of travel.
In navigation systems and in particular autonomous street toll data acquisition systems measured values, which can be obtained from sensors of the vehicle, are compared with known data which describes the track or course of the street. From this comparison it is in certain cases to be decided whether a toll road is actually being used. There is a requirement for the quality of this decision to be extremely high, since any erroneous decision either causes a loss in earnings to the road operator or—what, in practice, is perceived to be much more serious—a driver pays for the use of a road which he has not driven on.
In modern processes digital map data is employed, which describes attributes of a street, from which one assumes that a street differentiates itself sufficiently from a side street, so that these are not mistaken for each other. This assumption is verified by driving simulations and actual driving, and certain cases the data is corrected until a satisfactory result is achieved. The data so obtained is then used in actual operation as the basis for a decision algorithm of the system in the vehicles.
In isolated cases it could occur that the measured values which are obtained in the vehicle alone are not sufficient for distinguishing between the course of a toll street and another which is not a toll street or has a different toll. For such situations, so called support short-range data transmitters usually in the form of guide posts are employed, which respectively transmit supplemental information to the vehicle as to only one of the streets to be distinguished, so that complete information is available for the evaluation system to reliably make a decision.
Another possibility would be to relocate the point along a toll road segment at which a decision is to be made further along in the direction of travel. This way, one would have a greater chance of finding sufficient distinguishing characteristics between the two alternative street tracks. This does not in principal solve the problem; however, it reduces the number of the required information transmitting guideposts. In practice, however, such an improvement cannot be realized, since it should be possible also to conduct a spontaneous verification which is not limited to a location along an already “paid” section, and this along the greatest possible extent of the toll road. This leads to the requirement, that the decision point should be located as early as possible along a newly utilized road segment. This however again reduces the probability that in such a short road segment a clear distinction can be made, using vehicle obtained measurement values, between the road and another side road laying in close proximity.
In addition, there are further requirements for the evaluation process, such as a small as possible computation power requirement for the evaluation in a small auxiliary device in the vehicle, wherein the computation power should be distributed as evenly as possible over time.
It is accordingly the task of the invention to develop a suitable process which substantially overcomes the above mentioned problems. This task is solved in a process according to the precharacterizing portion of claim one by the characterizing features of claim one. Further details and advantageous embodiments of the inventive process are set forth in the dependent claims.
The invention will be described in the following on the basis of select examples with reference to the figures and the therein indicated reference numbers.
There is shown in:
In accordance with the invention, in the memory of the evaluation device a data set is maintained, which describes the course of the toll road going backwards as seen from the decision point relative to the direction of driving. The length of this described segment must be so long, that along this length one feature determinable by the measurement sensors detects the actually driven-on road, which feature is distinct from all other competing road courses in the vicinity. It is not possible at this time, using the vehicle onboard evaluation device, to determine which length of a stored street segment would be sufficient for this parameter, since this depends upon the respective course of all alternative streets. Thus it is the responsibility of the programmer who inputs the data sets for the evaluation device to provide sufficient information regarding competing street tracks in advance as the data set.
If all measurement values regarding the stored track up to the decision point lie within the tolerances of the sensors, then during the evaluation it is assumed that the described street segment is actually being traveled. Thereby it is assumed that no alternative streets exist of which the course is similar enough that one could travel along a longer segment thereof and during this all measurements within the tolerances could appear identical to those on the adjacent toll road.
In the case that the stretch of road under consideration going backwards from the decision point according to the above criteria leads to a branch so that more than one entry or approach exists to the traveled segment, then in accordance with the invention, as the data set, the respective course of the streets is described back to include all branches of this branching and this data set is included in the memory of the evaluation device. Therein, for the necessary length of each of these branches, likewise the condition of the first segment in the vicinity of the decision point applies (that a clear measurement difference exists).
Since however also these branches could again (viewed backwards in the direction of travel) lead to branches, this could result in a tree-like diversification of the data content to be carried along. For this, there applies for the necessary description of the segments of all branches after each other again the condition that the length must be sampled to the extent that the measured values from the sensors (within the tolerances) supply at least one clear result, which can only be associated with the actually traveled (for example) toll road.
For evaluation, in accordance with the invention, the measured values determined by the present sensors such as position, direction and orientation of the vehicle (and in certain cases also the elevation) are compared with data which describe the course of the in certain cases branch-like coming together, possible road courses leading to the decision point. Herein the data preferably is presented in the same form as the measured values, for example, in display format, from which the measured values can be derived, since a conversion can thereby substantially be omitted.
The data, which are made available in the vehicle are preliminarily to be so prepared that they provide the required minimum of information which allows the evaluation logic to clearly recognize the actually traveled segment from a consideration of all segments leading to the decision point by comparison with the sensor measurements. For this, the comparison of the different alternative segments inclusive of branches must be carried out so far back, until there can be no other driven course which does not lead to the decision point which, taking into consideration the measurement tolerances, can be confused with the relevant track.
The comparison between the input measured values and the existing data is preferably so carried out that segments of the (toll) road under consideration, which lie so close to adjacent roads as to be confused therewith (that is, within the tolerances of the sensor values), are less or not at all taken into consideration, and, in contrast, primarily the segments which deviate so far from competing tracks, that they, taking into consideration the sensor tolerances, can be clearly distinguished. Therein also a weighting of the data can occur, in the sense that a grading or categorizing of the relevance of the data with regard to the present (in certain cases vehicle dependent) measurement tolerances, and therewith the unambiguity of the differentiation, and therewith the distinction of the alternative segments, can be undertaken.
These parameters can already be taken into consideration during the selection of the data to be made available and for reducing the set of data to be brought along and for simplification of the control of the evaluation algorithm. All data, which (due to their likelihood of confusion) need not be present for evaluation could be omitted, other parts of the data can be provided with parameters, which characterize the weight of this segment in an evaluation. With this variable weighting of the data for the comparison between measurements and descriptions of the various street tracks or courses one can rapidly and confidently compare long courses and branches, since competing streets are thereby represented by detailed data sets and thus can reliably be distinguished from one of the relevant tracks. The selection of the data or as the case may be the parameterization thus contributes essentially to the function of the evaluation algorithm.
In employment of the inventive process the street course must be described backwards to the direction of travel from the decision point, and be present in the data set of the evaluation device, so far until it so distinguishes itself from the competing street b, that it can no longer be confused with the detected measured values despite inherent tolerances. It can be seen from this example that the description of the course a is not sufficient. If for an evaluation only the segment a is known and the vehicle is actually traveling along path c-f-b, then the tolerances of the measurement results are not sufficient to provide an unambiguous decision. This shows that here the description of the course of the toll road against the direction of travel must occur out along at least one branch. Thus these branches must also be described to the extent that taking into consideration the tolerances the described branch and the rest of the paths up to the decision point they cannot be confused with another street track (clear differentiation of the measured values).
In the illustrated example according to
In accordance with the above-described requirements the set of data to be carried along in the evaluation unit should be as small as possible, in order to reduce memory and transmission costs. In any case, the data set must describe the course of the street up to the locations at which the competing tracks are sufficiently distinguishable, such that they can be reliably separated using the on-hand measuring devices. In the discussed example in the case of the corresponding tolerance ranges of the sensors the measured values on both competing street segments a and b could lead to the result that the toll road is being traveled upon. The measured values from these road segments hardly contribute to the decisive determination. From this one can conclude that the precise characterization of the course of the relevant road segment at these locations is not necessary. One can thus omit a description of these locations and limit oneself to other parameters or correlation considerations, such as distance or time window, and upon data elements, which describe the course of the actually relevant locations.
The representation in
As long as the measured values remain within the predetermined precision, it then is valid that on a competing road or side street a measurement can be produced, which could also have been measured on the toll-relevant road segment, even if all stipulated tolerances likewise have been utilized or exploited here. As a rule of thumb here it could be valid for example that the distance of the competing roads or as the case may be directions must be an amount that is more than twice the combined precision. This corresponds for the considered example to a data set which is present by the segments described in
An even more encompassing description of the street relationships going beyond this minimal set can without more be put into direct employment. Thus, for example, also a data set can be employed, which was conceptualized for navigation applications. Therewith a consideration of the evaluation results as to consistency with these other map data can occur. A broader data set can also be employed in order to make possible a continuation of the measurements by “map matching” during a temporary loss of position sensors (for example in tunnels).
The algorithm used in the evaluation device must recognize the traveling of the complete course of the relevant sequence of streets, that is, from the beginning of the “branch” until a (for all branches common) decision point. An average data storage regarding the total course does not suffice in the case of longer segments. An advantageous method would be either to evaluate each measured value separately, for example whether it lies within or outside the agreed tolerances, or over short street segment “packets” of common measured values, for example, to evaluate with a “least square” file, in order to discount individual “outliers”.
The central service center, which describes for compilation of the data set the course of the street, taking into consideration the measurement tolerances of the evaluation devices, must, besides the precise agreement of the measurement tolerances, also precisely define the format which is used for transmission of these data into the evaluation device. Therein this format should be the same for all recognition locations, even if, due to the different conditions with regard to adjacent streets, the structures for these minimal data sets would be different. Further, the format of the data set should be so selected that in the evaluation device always the same algorithm or as the case may be the same software can be employed for the evaluation.
In accordance with the invention the expected diversity of the structures can be described by minimally described street courses in a recursive structure of “sequences” which form optional branches and then again plots or progressions.
The characteristics of an optimal coding of individual road segments to be recognized, for example, toll roads, can be described as follows:
Number | Date | Country | Kind |
---|---|---|---|
10 2005 039 584.8 | Aug 2005 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/EP2006/008043 | 8/15/2006 | WO | 00 | 2/19/2008 |