A Decision-Rule Topological Map-Matching Algorithm with Multiple Spatial Data - Global Navigation Satellite Systems: Signal,Theory and Applications - page 224

The shortest path between points S0 and S2 is computed using network topology and
allowable turns. Consequently, the speed comparison shown in Table 1 is performed to
determine if this path is feasible. In this case, the obtained path is feasible since the
difference between the average calculated and recorded speeds (26.8 and 31.5 mi/h,
respectively) is within tolerance (25 mi/h). Therefore, the current snapped positions for
points 0 and 2 are initially assumed to be correct. The main algorithm continues by finding
the shortest path between the next pair of snapped points, S2 and S3. This path is not
feasible when using network topology because if the vehicle was located at S2, it would
have to exit the ramp and travel approximately 5,125.9 feet in 5 seconds at an average speed
of 699 mi/h to reach snapped point S3. Hence, either point S2 or S3 or both were snapped to
an incorrect roadway centerline. The map-matching algorithm now obtains the shortest path
between points S3 and S4 and determines that the difference between calculated and
average recorded speeds with values of 29 mi/h and 35 mi/h, respectively, is within
tolerance. Therefore, an alternative roadway centerline is sought within the buffer around
point 2. Interstate 39 is found to be the next nearest roadway, resulting in alternative point
alt2, shown as a triangle in Figure 6. Consequently, feasibility is checked for paths between
the preceding points S0 and alt2, and between alt2 and its successor, snapped point S3. As
indicated in Table 1, both computed shortest paths are feasible. The calculated speeds along
these paths are within 25 mi/h of their respective average recorded speeds for the vehicle.
Therefore, the spatial ambiguity at the diverging roadway is resolved and the correct
roadway for point 2 is Interstate 39. Data point S1 is then obtained by snapping point 1 to
the Interstate 39 centerline.
Fig. 6. Example of Map-Matching Algorithm at Diverging Roadways