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Application of Portable 3D Laser Scanner In Building Facade Survey
Building facade measurement is an important work in the old house reconstruction project, and it is also the difficulty point in the work of building “city business card” and “lighten up the block”.
Traditional building facade measurement uses prism-free total station to obtain 3D point coordinates of key positions of buildings, combined with measuring tape and rangefinder to measure the detail dimensions, manual sketch, and uses high-definition camera to take pictures of building facade texture.
I. Project Introduction
The emergence and development of 3D laser scanning measurement technology overcomes the limitations of traditional building facade measurement method. It is no longer a measurement mode of building length, width and height by using tape measure, rangefinder and other simple tools, but it is a high efficient measurement method that can scan buildings quickly and accurately without contact, at the same time, the obtained point cloud information is quickly transformed into data that can be processed by computer. It solves the problems of accuracy loss and efficiency loss caused by manual collection of building facade data, especially the problem that the facade elements of high-rise buildings cannot be measured.
In August 2021, in the facade renovation measurement project of a street in Anhui province, Wuhan Hi-Cloud Technology Co.,Ltd. uses 3D laser scanner to measure the facade of the buildings, so as to quickly and accurately provide the basic elevation for the relevant design departments.
1.Hardware recommended is HD TLS360 from Wuhan Hi-Cloud Technology Co.,Ltd
|Max. Measurement Range||150m|
|Min. Measurement Range||0.2m|
|Scan Point Rate||320,000pts/s|
|Panoramic Resolution||18M Pixels（External camera）|
|Duo Axis Compensation||±5°|
|Date Transmission||GigE/TF Card|
|Control Mode||Mobile terminal remote control|
HD TLS SCENE
3D laser point cloud processing software HD TLS SCENE
Hi-Cloud 3D laser point cloud processing software is a leading professional point cloud processing platform software. This software product provides multi-station registration, point cloud rendering browsing, point cloud denoising, point cloud quality inspection, filtering classification, point cloud coloring, 3D terrain model generation, feature extraction survey and other kinds of 3D laser point cloud professional processing and analysis functions.
Lasre point cloud processing software
HD PtCloud Vector
Point cloud digital mapping software HD PtCloud Vector
HD PtCloud Vector software is a professional symbolic digital mapping and database building software developed based on AutoCAD platform. Using 3D laser point cloud and real scene data, through a variety of interpretation and acquisition functions, it can quickly and easily extract feature information, and provide users with a whole process mapping and database building solution from mapping, updating to database building, which meets the needs of various professional or industry mapping and database building requirements.
HD PtCloud Vector
Facade drawing based on HD PtCloud Vector
II. Project Requirements
The 3D laser scanner is used to carry out 3D digital measurement of the building facade within the scope of the street facade renovation project, and the point cloud model and color digital orthophoto map within the scope of the project are obtained.
The technical service mode is on-site point cloud data collection and lpost mapping drawing. The data achievements are point cloud data, DWG format files, E-files and paper files of facade mapping, and meet the requirements of clear pictures and detailed data. The overall registration accuracy of the point cloud provided is less than 5cm, which should meet the requirements of facade renovation construction drawing and engineering quantity calculation.
The main work of building facade measurement includes: to measure the plane location, window sill, foundation elevation, roof height and other elements of the housing within the survey area, and draw the elevation map. The technological process flow of facade measurement using 3D laser scanner mainly includes two parts: internal and external work. The specific work steps are as follows:
Basic work flow
IV. Data acquisition and internal work result
When using HD TLS360 for data acquisition, pay attention to the station sequence during scanning.
Since the survey area is large and there are many trees, it is necessary to scan by multiple stations. The following requirements shall be met when setting stations:
1、The whole survey area shall be covered with as few stations as possible, ranging above 50m shall be selected, and 30% overlap area shall be retained to facilitate data registration.
2、Set the survey station at a high position directly opposite to the building and scan the building to obtain more target points and avoid blind areas.
Multi-station registered point cloud
The unified point cloud data is the overall data containing the 3D coordinate information of all features within the survey station area. The effective data of each independent building can be obtained by cutting the point cloud. In order to correctly project the facade data of each building onto the 2D plane, it is necessary to establish a spatial coordinate system based on the facade data of the building.
Drawing process display
V. Technical Advantages
In building facade measurement operation, the method of using 3D laser scanner has the advantages compared with the method of single point 3D data acquisition by total station:
Different measured targets: the traditional way can only measure the point coordinates of the position of the reflection prism, and the measured object must be where the prism can reach. It is difficult to measure the dangerous area or the area that is difficult for the surveyor to reach. 3D laser scanning can work without contacting the measured object.
Different observation environment: the traditional measurements must be made during the day or in brighter places because the prism need to be aimed. And 3D laser scanning measurement can be carried out all-weather all day, and the night scanning effect is better.
Different amount of data obtained: the traditional method can only obtain the feature points of the target to a limited extent. The 3D laser scanner can obtain massive data of high-density observation targets, with high sampling rate and detailed description of objects.
Improved operating efficiency: it has been proved by practice that the operation efficiency of 3D laser scanner is more than 7 times higher than that of traditional total station.