Line segment vacuating device for electronic map and method thereof

Abstract

The invention discloses a line segment vacuating device for an electronic map and a method thereof. The device comprises a map lead-in module, a threshold value setting module, a vertical distance calculating module, an included angle calculating module and a line segment vacuating module. A straight line enabling a head point PS of a curve to be connected with a tail point PE of the curve serves as a datum line, the maximum vertical distance dm from other end points on the curve to the straight line PS-PE is calculated, the point with the maximum vertical distance is recorded as Pm, an included angle alpha formed by the vector PS-Pm and the vector Pm-PE is calculated out, compared the dm with the D, the a and the A, if dm<=D and a <=A, then only the head point PS and the tail point PE of the curve are retained, all other points are removed; if dm> D and a>A, then the Pm point separates the curve into two portions, vertical distance calculating, included angle calculating and line segment vacuating are repeatedly carried out on the two portions, until the dm>=D and a>=A. The line segment vacuating device can not only guarantee vacuating vigor and certain compression ratio, but also give consideration to vacuating deformation and guarantee smoothness of line segment after vacuating, and cannot enable original line forms to be excessively distorted.

Description

technical field [0001] The invention relates to the field of GIS data and image data processing, in particular to a data compression method based on polylines, in particular to a line segment thinning device and method for electronic maps. Background technique [0002] In the process of processing electronic maps, taking embedded vehicle navigation equipment as an example, due to the limitation of external storage and internal memory capacity, it is always necessary to thin out the map data for display when the display function requirements are met. to reduce the map size. The Douglas-Puke method (DP algorithm for short) in the traditional vector data compression method is more commonly used, and its basic idea is as follows: figure 1 Shown: A dashed straight line is connected to the first and last points of each curve. Find the distance between all points and the straight line, and find the maximum distance value dmax. Use dmax to compare with the threshold D; if dmax>D,...

AI Technical Summary

Problems solved by technology

[0004] The technical problem to be solved by the present invention is to overcome the defects of low compression rate in places with small curvature and serious distortion in places with large curvature in the prior art, and provide a method for electronic maps that takes into account both compression rate and smoothness. Line segment thinning device and method thereof

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