Encoding data generation method and device
First Claim
1. A method of coding a linear object represented by a string of latitude and longitude coordinates, the method comprising:
- sampling the linear object at a constant length;
representing the sampled linear object by two elements of the constant length and a data of angles, each angle being determined by a line from a first point to a downstream point;
converting the data string of the angles into a data string of deflection angles, each deflection angle showing a direction difference between a line from a second point to a downstream point and another line from an upstream point to the second point;
converting the data string of deflection angles into a data string of predicted difference values, each predicted difference value being provided by obtaining a difference between a predicted deflection angle on a third point predicted by a prediction formula using a deflection angle on an upstream point and the actual deflection angle of the third point; and
variable-length coding the data string of the predicted difference values.
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Abstract
In a coded data generation method of resampling a road shape for setting a plurality of nodes, arranging position information of each node represented by a deflection angle from the immediately preceding node to generate a data string of the deflection angles, converting the deflection angles into predicted difference values each indicating the difference from the predicted value, and variable-length coding the data string of the predicted difference values, the data string of the predicted difference values when the deflection angles are converted into the predicted difference values is evaluated and a prediction expression to calculate the predicted value is selected adaptively from among a plurality of prediction expressions φ=1, φ=2, φ=3, and φ=4 based on the evaluation result. The prediction expression to calculate the predicted value is selected adaptively in response to road shape A, B, C, D, so that the data compression effectiveness is enhanced.
15 Citations
10 Claims
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1. A method of coding a linear object represented by a string of latitude and longitude coordinates, the method comprising:
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sampling the linear object at a constant length; representing the sampled linear object by two elements of the constant length and a data of angles, each angle being determined by a line from a first point to a downstream point; converting the data string of the angles into a data string of deflection angles, each deflection angle showing a direction difference between a line from a second point to a downstream point and another line from an upstream point to the second point; converting the data string of deflection angles into a data string of predicted difference values, each predicted difference value being provided by obtaining a difference between a predicted deflection angle on a third point predicted by a prediction formula using a deflection angle on an upstream point and the actual deflection angle of the third point; and variable-length coding the data string of the predicted difference values. - View Dependent Claims (2, 5, 6, 7, 8, 9)
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3. A transmission apparatus for coding a linear object represented by a string of latitude and longitude coordinates, the transmission apparatus comprising:
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a sampling unit for sampling the linear object at a constant length; a representing unit for representing the sampled linear object by two elements of the constant length and a data string of angles, each angle being determined by a line from a first point to a downstream point; a converting unit for converting the data string of the angles into a data string of deflection angles, each deflection angle showing a direction difference between a line from a second point to a downstream point and another line from an upstream point to the second point; a converting unit for converting the data string of the deflection angle into a data string of predicted difference values, each predicted difference value being provided by obtaining a difference between a predicted deflection angle on a third point predicted by a prediction formula using a deflection angle on an upstream point and the actual deflection angle of the third point; and a coding unit for variable-length coding the data string of the predicted difference value. - View Dependent Claims (4, 10)
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Specification