Generalization of features in a digital map
First Claim
1. A method for generalizing a feature of a digital map, the feature including a polyline, the polyline including a plurality of shape points, the method comprising:
- creating, by a computer, a set of nodes by, for each pair of shape points in the polyline;
determining, by the computer, whether a chord from the first shape point of the pair to the second shape point of the pair is acceptable;
responsive to the chord being acceptable, creating, by the computer, a node representing the chord;
creating, by the computer, a set of links by, for each pair of nodes in which the second shape point in one node is the same shape point as the first shape point in the other node;
determining, by the computer, a first angle, the first angle formed by the polyline at the shape point;
determining, by the computer, a second angle, the second angle formed by a transition from the chord represented by the first of the pair of nodes to the chord represented by the second of the pair of nodes;
comparing the first angle and the second angle to determine whether the transition having the second angle is acceptable;
responsive to the transition being acceptable, creating, by the computer, a link between the pair of nodes;
for each path from a node including the first shape point in the polyline to a node including the last shape point in the polyline, determining a cost of the path based on a cost associated with each node and a cost associated with each link; and
generating, by the computer, as a simplified polyline the polyline represented by the path having the least cost.
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Accused Products
Abstract
Generalization of features in a digital map is enabled by performing a simplification of polylines. A set of chords between points on a polyline is selected such that each chord does not violate specified rules such as maximum distance from the original polyline. If a chord is acceptable, a node representing the chord is created, described by the start and end points of the chord. For pairs of nodes created, a transition from the first node to the second node is evaluated to determine whether it is acceptable. In one embodiment, a transition is acceptable if the absolute value of the angle formed by the chords is within a threshold angle from the angle formed by the original polyline at that point. If the transition is acceptable, a link between the two nodes is established. A least-cost path through the graph is chosen, and a simplified polyline is then generated.
16 Citations
18 Claims
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1. A method for generalizing a feature of a digital map, the feature including a polyline, the polyline including a plurality of shape points, the method comprising:
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creating, by a computer, a set of nodes by, for each pair of shape points in the polyline; determining, by the computer, whether a chord from the first shape point of the pair to the second shape point of the pair is acceptable; responsive to the chord being acceptable, creating, by the computer, a node representing the chord; creating, by the computer, a set of links by, for each pair of nodes in which the second shape point in one node is the same shape point as the first shape point in the other node; determining, by the computer, a first angle, the first angle formed by the polyline at the shape point; determining, by the computer, a second angle, the second angle formed by a transition from the chord represented by the first of the pair of nodes to the chord represented by the second of the pair of nodes; comparing the first angle and the second angle to determine whether the transition having the second angle is acceptable; responsive to the transition being acceptable, creating, by the computer, a link between the pair of nodes; for each path from a node including the first shape point in the polyline to a node including the last shape point in the polyline, determining a cost of the path based on a cost associated with each node and a cost associated with each link; and generating, by the computer, as a simplified polyline the polyline represented by the path having the least cost. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A computer program product for generalizing a feature of a digital map, the feature including a polyline, the polyline including a plurality of shape points, the computer program product stored on a non-transitory computer readable medium and including instructions configured to cause a processor to carry out the steps of:
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creating a set of nodes by, for each pair of shape points in the polyline; determining whether a chord from the first shape point of the pair to the second shape point of the pair is acceptable; responsive to the chord being acceptable, creating a node representing the chord; creating a set of links by, for each pair of nodes in which the second shape point in one node is the same point as the first shape point in the other node; determining a first angle, the first angle formed by the polyline in the shape point; determining a second angle, the second angle formed by a transition from the chord represented by the first of the pair of nodes to the chord represented by the second of the pair of nodes; comparing the first angle and the second angle to determine whether the transition having the second angle is acceptable; responsive to the transition being acceptable, creating a link between the pair of nodes; for each path from a node including the first shape point in the polyline to a node including the last shape point in the polyline, determining a cost of the path based on a cost associated with each node and a cost associated with each link; and selecting as a simplified polyline the polyline represented by the path having the least cost. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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Specification