Abstract: There is provided a method for identifying possible errors/inconsistencies within an electronic map representation of a network of navigable elements within a geographic area, the method comprising: obtaining at a server positional data relating to the movement over time of a plurality of devices travelling around the navigable network; processing the obtained positional data at the server with reference to the electronic map representing the navigable network in order to identify potential inconsistencies in the map in the form of one or more locations within the navigable network where an observed behaviour of devices travelling around the navigable network as indicated by the obtained positional data is not consistent with a behaviour that would be expected based on the electronic map. This information may then be relayed to navigation devices for supplementing the electronic map when generating navigation instructions.

Abstract: Photographic images recorded with mobile mapping vehicles (20) in real life situations usually contain cars or other moving objects (34) that cover visual information on the road surface (24). According to the techniques of this invention, moving objects (34) are detected by grayscale differencing in overlapping pixels or sections of two or more orthorectified image tiles. Based on moving object identification, masks are generated for each orthorectified tile. The masks are then compared and priorities established based on grayscale values associated with the masks. Mosaics of a large surface of interest such as the Earth can be assembled from a plurality of overlapping photographic images with moving objects (34) largely removed from the resulting mosaic.

Abstract: A method for determining barrier crossing information for convoyed objects (22) using historic trajectory data (28). Trajectories (28) having similar geographical and directional properties are bundled so that trajectory density can be measured as a function of position and time (s, t). Visual presentation of the trajectory information can be used to determine certain types of barrier crossing information useful in a digital map. Frequency analysis on a number of trajectory density time series may be performed to determine specific barrier crossing locations (26) through the detection of vehicle bursts. Such frequency analysis may also indicate barrier crossing times and schedules in the case of crossing patterns.

Abstract: A method for realigning network elements in a digital map based on a new data set using active contour manipulation techniques. The active contour optimization process is controlled so that certain desirable features in the original shape of the active contour(s) are not distorted. In the case of network features which may be represented by two or more open active contours, the active contours are coupled prior to optimizing so that the original desirable shape, e.g., the parallel spacing of lanes in a dual carriageway road, may be maintained during the optimization process. In the case of certain closed active contours, for example roundabout geometries, a single closed active contour may be coupled to itself by linking its control points one-to-another and maintaining a proportional direction and distance movement during the optimizing process. As a result, data base networks can be assessed and aligned with less difficulty and geometric distortion.

Abstract: A method for updating speed limit, service stop location, or other attributes for road segments in a digital map (18) by extrapolating probe data from a subset of probe data which has been profiled to have originated from trustworthy probe traces. Probe measurements from a plurality of probes is collected and profiled against known information. From this, a subset of trustworthy probes is identified, comprising those probe traces which observe the known attribute of interest within an acceptable range for a majority of the driving time. These trustworthy probe traces are tracked during travel on other road segments whose attribute data is unknown or unreliable. A specification for the unknown or unreliable attribute on the other road segments can be extrapolated based on the collected information from all of the trustworthy probe traces as they travel that road segment. The digital map (18) can then be updated by setting attribute information in relation to the extrapolated behavior data.

Abstract: A method for determining the existence of an underpass (21) in a digital map by observing probe data is provided. The method includes providing a digital map having at least two road segments (18, 20) and reporting data from a plurality of probe traces traveling along the at least two roads segment (18, 20). Further, analyzing the reported data for dilution of precision (DOP) values. Then, inferring the existence of an underpass (21) along one (18) of the at least two road segments (18, 20) if the DOP values suddenly decrease from a substantially constant value to a decreased value and then suddenly return to the substantially constant value.

Abstract: A method for determining barrier crossing information for convoyed objects (22) using historic trajectory data (28). Trajectories (28) having similar geographical and directional properties are bundled so that trajectory density can be measured as a function of position and time (s, t). Visual presentation of the trajectory information can be used to determine certain types of barrier crossing information useful in a digital map. Frequency analysis on a number of trajectory density time series may be performed to determine specific barrier crossing locations (26) through the detection of vehicle bursts. Such frequency analysis may also indicate barrier crossing times and schedules in the case of crossing patterns.

Abstract: Photographic images recorded with mobile mapping vehicles (20) in real life situations usually contain cars or other moving objects (34) that cover visual information on the road surface (24). According to the techniques of this invention, moving objects (34) are detected by grayscale differencing in overlapping pixels or sections of two or more orthorectified image tiles. Based on moving object identification, masks are generated for each orthorectified tile. The masks are then compared and priorities established based on grayscale values associated with the masks. Mosaics of a large surface of interest such as the Earth can be assembled from a plurality of overlapping photographic images with moving objects (34) largely removed from the resulting mosaic.

Abstract: A method for realigning network elements in a digital map based on a new data set using active contour manipulation techniques. The active contour optimization process is controlled so that certain desirable features in the original shape of the active contour(s) are not distorted. In the case of network features which may be represented by two or more open active contours, the active contours are coupled prior to optimizing so that the original desirable shape, e.g., the parallel spacing of lanes in a dual carriageway road, may be maintained during the optimization process. In the case of certain closed active contours, for example roundabout geometries, a single closed active contour may be coupled to itself by linking its control points one-to-another and maintaining a proportional direction and distance movement during the optimizing process. As a result, data base networks can be assessed and aligned with less difficulty and geometric distortion.

Abstract: A method for updating speed limit, service stop location, or other attributes for road segments in a digital map (18) by extrapolating probe data from a subset of probe data which has been profiled to have originated from trustworthy probe traces. Probe measurements from a plurality of probes is collected and profiled against known information. From this, a subset of trustworthy probes is identified, comprising those probe traces which observe the known attribute of interest within an acceptable range for a majority of the driving time. These trustworthy probe traces are tracked during travel on other road segments whose attribute data is unknown or unreliable. A specification for the unknown or unreliable attribute on the other road segments can be extrapolated based on the collected information from all of the trustworthy probe traces as they travel that road segment. The digital map (18) can then be updated by setting attribute information in relation to the extrapolated behavior data.