Mean elevation plane triangulated irregular network-based topographic map elevation sparsing algorithm

Abstract

The invention relates to a mean elevation plane triangulated irregular network-based topographic map elevation sparsing algorithm. The sparsing algorithm comprises the following steps of constructinga triangulated irregular network; obtaining a mean elevation plane; setting a threshold; reconstructing the triangulated irregular network; calculating an elevation gradient; screening feature elevation points; obtaining an extreme value of the elevation points; setting a height difference and a distance threshold; and deleting the triangulated irregular network, wherein the triangulated irregularnetwork (TIN) refers to the triangulated irregular network generated by adopting a Delaunay triangulated network. According to the triangulated irregular network-based topographic map elevation pointsparsing algorithm, the elevation points capable of remarkably reflecting topographic relief change are reserved as far as possible, and the topographic change in a sparsing range is better expressed; the elevation points can be averagely distributed in a map, and the local topographic relief condition with remarkable and tiny height difference change is better reflected; and by utilizing methodsof the mean elevation plane, the elevation gradient and the like, the elevation points are screened and sparsed to achieve a reasonable topographic map downsizing effect.

Description

technical field [0001] The invention belongs to the field of thinning of elevation points in the process of compiling a series of scale topographic maps, in particular to a thinning algorithm of elevation points using TIN, average elevation surface and elevation gradient. Background technique [0002] In the process of downsizing a series of scale topographic maps, especially when a large-scale topographic map is reduced to a small-scale topographic map, the problem of thinning of elevation points is often encountered. In order to achieve a more reasonable downsizing effect, the traditional thinning usually requires Consider the distribution density of elevation points and terrain relief. At this stage, the method of TIN is mostly used to screen and thin the elevation points, but this method is relatively simple, and it is difficult to achieve a better downsizing effect. [0003] Digitizing the original large-scale topographic map is one of the important ways to obtain topo...

AI Technical Summary

Problems solved by technology

This method has two main disadvantages: 1. Points with large curve changes may be compressed due to thinning, resulting in curve deformation; 2. Some redundant points will be left behind and cannot be deleted.

Compared with the above two methods, the thinning accuracy of the Douglas-Puke algorithm is significantly improved. First, because the threshold value generally takes the maximum allowable error of the corresponding object, and second, because the algorithm can achieve a better balance between deletion and retention. Balance, that is, the number of points can be sufficiently reduced, and the feature points can be retained as much as possible, but because loops or recursion are used in programming implementation, when the number of points is large, the efficiency will be affected

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