A method for automatically extracting ancient city wall data from lidar point cloud data based on city wall sections

Abstract

The invention relates to a method for automatically extracting ancient city wall data from LiDAR point cloud data based on a cross section of a city wall. The method comprises the steps of acquiring and vectorizing a candidate region of a city wall to obtain a top two-dimensional centerline, and conducting interpolation to obtain a complete city wall top three-dimensional centerline; conducting dense sampling for the city wall top three-dimensional centerline to acquire detecting base points, and calculating the point cloud on each probe base point cross section; constructing a city wall cross section grid; and based on the city wall cross section, detecting horizontally-longitudinally point cloud data at the top, crenel and side of the city wall. The invention provides the method for extracting the ancient city wall data using LiDAR point cloud data, solves the problem in key technology of digital archiving using LiDAR technology, and effectively overcomes the deficiencies of consuming too much time and labor in traditional measurement and failing to acquire detailed information on the side of the city wall. The method for accurately extracting city wall side points via longitudinal-horizontal detection in the invention can effectively achieve automatic acquisition of detailed information of the side of the city wall and the top information.

Description

technical field [0001] The invention relates to a method for extracting city wall point cloud data, in particular to a method for extracting city wall point cloud data from LiDAR point cloud data based on a city wall section. Background technique [0002] The ancient city wall is an important part of Chinese cultural heritage and has important historical and cultural value. However, due to man-made damage, war destruction, natural weathering, flood damage, etc., the ancient city wall is suffering serious damage. Digital archiving of the ancient city wall is an important means of protection, which is not only conducive to understanding the current situation of the ancient city wall, but also has important guiding significance for the reconstruction and protection of the ancient city wall, and also plays an important role in the display and publicity of the ancient city wall. [0003] The purpose of the city wall structure is to defend the city. It is usually built according ...

AI Technical Summary

Problems solved by technology

[0004] 1) A combination of traditional measurement and image measurement is used in the measurement. Traditional measurement can only measure discrete point and line information, and it is impossible to collect data covering the irregularly changing side details of the city wall "narrow at the top and wide at the bottom" Due to the constraints of satellite image resolution and two-dimensional characteristics, image measurement cannot realize lateral information collection;

[0005] 2) The height of the city wall is measured in sections, and the overall height of the city wall cannot be obtained completely, which is not conducive to grasping the height change of the city wall, and is not conducive to the timely update and digital archiving of the city wall information

The point cloud extraction of the city wall includes the extraction of top and side point cloud data, but the structure of the city wall "narrow at the top and wide at the bottom" makes the side point cloud and the ground point cloud at the junction, the elevation mutation is not obvious, and the side is not nonlinear. The rules change, so it is difficult to extract the city wall point cloud with the existing algorithm

[0008] 2) if figure 1 As shown, the city wall point cloud data is missing and has other interference

Occlusion results in incomplete data on the side of the city wall, and where there is missing side data, there are usually adjacent vegetation or shacks and houses (such as figure 1 shown), causing interference to the city wall point cloud data

The lack of data and the interference of other ground objects further increase the difficulty of extracting the side of the city wall

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