Patent ID: 7528746

Claim:
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.