Rapid extraction method for dense point cloud oriented toward city three-dimensional modeling

Abstract

The invention provides a rapid extraction method for dense point cloud oriented toward city three-dimensional modeling. The rapid extraction method comprises the steps of: 1) preparing data; 2) establishing a coordinate grid; 3) converting an image into a gray scale image; 4) judging whether a difference value between a gray value of each target pixel point and a gray value of a neighborhood pixel point is greater than a threshold value A, if so, regarding the target pixel point as a candidate angular point, and if not then rounding; 5) calculating a corner response function (CRF) value of the candidate angular point, and judging whether the CRF value of the candidate angular point is greater than a threshold B, is so regarding the candidate angular point as a feature point, and if not then rounding; 5) matching homonymy points; 7) generating seed points; 8) conducting regional diffusion; 9) conducting gross error elimination; 10) and generating dense point cloud to form a tin for establishing a three-dimensional model. Compared with the prior art, the rapid extraction method provided by the invention has the advantages of small error, high precision, high operation efficiency, wide application extension and the like.

Description

technical field [0001] The invention relates to a method for extracting dense point clouds, in particular to a method for rapidly extracting dense point clouds for three-dimensional modeling of cities. Background technique [0002] Oblique photography technology is a high-tech developed in the field of international surveying, mapping and remote sensing in recent years. By carrying multiple sensors on the same flight platform (currently, five-lens cameras are commonly used), images are collected from different angles such as vertical and oblique at the same time. More complete and accurate information about objects. The images captured at a vertical angle to the ground are called positive films (a group of images), and the images captured at a certain angle between the lens and the ground are called oblique films (four groups of images), which are oblique images; among them, oblique images have the following Features: (1) It can obtain images from multiple viewpoints and an...

AI Technical Summary

Problems solved by technology

[0032] a) In the application of rapid urban modeling, the current dense point cloud extraction method based on oblique images affects the accuracy of 3D modeling, and the extraction method process still needs to be improved;

[0033] b) It takes about three to five months for the modeling of small and medium-sized cities to adopt the oblique image modeling method. The Harris algorithm used in the process of extracting dense point clouds from multi-view images needs to detect each pixel in the process of detecting corner points. Corner response detection, which involves a large number of multiplication operations, resulting in slower calculation speed and affecting work efficiency

[0034] c) There are many error points in the point cloud obtained after the multi-view image dense point cloud extraction and seed point diffusion. The existence of error points will change the geometric shape of the ground object, which has a great impact on the subsequent 3D modeling

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