Innovating as-built verification

作者：Yoshie Katagiri

2018年,日本国土,Infrastructure and Transport (MLIT) publicly invited bids for a ‘Project to Introduce and Utilise Innovative Technology to Dramatically Improve Productivity on Construction Sites’ under its i-Construction initiative aiming to boost productivity on construction sites as part of a wider innovation strategy. Kanatsu Giken formed a consortium of four companies with Fukui Computer Co., Ltd., Leica Geosystems Co., Ltd., and Sanyo Sokki Co., Ltd., and tendered for the project. The consortium was selected in the category of ‘Techniques Using Data to Improve the Productivity of Construction in Civil Engineering Work.’

四公司联盟的目的是在混凝土结构（例如桥梁基台和码头）上进行3D激光扫描，并使用获得的点云数据进行实行验证，以显着提高施工地点的生产率。此外，他们使用捕获的点云数据与3D设计数据（CIM）的坐标值之间的差异进行了试验并提出了一种新的进度管理方法。

Kanatsu Giken used Leica Geosystems’Leica Nova MS60 MultiStation，一种具有3D激光扫描的仪器，并具有常规总站的测量功能。

“Current as-built verification method is time-consuming and labour intensive because much of the measurement and analysis of disparities is done manually. The reason we bought the Nova MS60 in the first place, was to make these tasks less labour intensive. Soon after the purchase, we found out about the MLIT project. We focused the expertise available across the four companies and came up with a specific method for construction management using points and surfaces. This also had the potential to enable high productivity when verifying the as-built, so we tendered for the project,”describes Yoshinobu Kimura, team leader of the information technology group in the civil engineering division at Kanatsu Giken.

The consortium conducted field measurements and data analysis at five sites and based on the results, compiled and submitted recommendations to MLIT. In 2019, MLIT announced their evaluations of all submitted projects – this consortium won an ‘A’ rating, the highest evaluation.

点云数据之间的比较obtained by measuring the as-built of cast-in-place piles and 3D design data (blue lines)

平面（粗糙度）对点云数据的比较评估，通过测量与3D设计数据的地位桩的构建

点云数据之间的比较obtained by measuring the as-built of footing and design data (blue lines)

Planar (roughness) comparative evaluation of point cloud data obtained by measuring the as-built of a footing against the 3D design data

By conventional techniques, it takes a total of three people - a pair taking measurements and a photographer - to measure the as-built of the cast-in-place pile.

使用试用技术，一个人可以操作NOVA MS60进行测量和摄影.The trial techniques reduced the number of man-hours required for measurements of cast-in-place piles by more than half.

The footing is a reinforced concrete foundation with shock-absorbing function. As it is chamfered, reading of accurate corner points can be an issue.

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Manhours for measurement work halved

In the case of piers, due to the requirement to take measurements at height and in confined spaces，使用3D点云数据进行平面评估非常有用。

The trial was run for the as-built measurement and verification during the construction works on two bridge abutments and two bridge piers of the outer and lower portions of the Ohguni Viaduct in Japan. The results from the trial were divided into cast-in-place piles, footings, and housings.

To be able to efficiently conduct accurate as-built verification of the entire top of the pile was one of the great advantages of the trial technology.

“使用常规方法，当我们测量桩顶的标准高度时，我们使用了一个梯子或类似的东西，类似于爬过桩从桩上伸出的增援，并在中心有一个测量师。桩直径通过两个团队测量，以两个方向进行测量 - 一个沿着桥的轴，另一个垂直于此。这项工作一次又一次地重复，直到测量所有桩。需要另一个工人拍摄剩余的验证过程的照片。

With the Nova MS60, you can measure from outside the steel reinforcements. It’s no longer necessary for surveyors to work in pairs to measure the pile cores and pile diameters with tape measures and then calculate the central points, as these can be accurately determined later by data analysis,”explains Kimura.

The MultiStation reduced the manhours required for the measurement work to less than half. Worker downtime got reduced from 83.3 manhours with the conventional techniques to 37.27 hours.

In addition, because the data captured by the Nova MS60 is uploaded to the point cloud processing system for the as-built measurements, there is no need to take photos for as-built verification separately. This also eliminated the time involved in organising the photos after the work on site.

基础是放置在铸件桩顶部的钢筋混凝土的基础。在审判中，脚手架被证明是一个障碍。码头坐在立足点上并支撑桥接的上层建筑。

For the piers and footing, scaffolding proved to be an obstacle and the instruments had to be moved frequently. In spite of this, the trial task took 8.5 manhours compared with the 11 manhours for the footing and 30.9 manhours compared with the 40 manhours taken with conventional techniques.

Comparison of point cloud data obtained by measuring the finished shape of the pier and the design data (blue line)

Planar (roughness) comparative evaluation of point cloud data obtained by measuring the as-built of a pier against the 3D design data

“For footings and piers, we only managed a manhour reduction of around 20 per cent. But in cases where there are many structures to measure, even 20 per cent represents a substantial saving. Also, if 3D laser scanning is established as a standard process, construction sites will devise workflows for building and removing scaffolding so that measurements can be performed efficiently, and this should reduce manhours even further,”says Kimura.

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Use of point cloud data boosts productivity increases accuracy and improves safety

这种使用Point Cloud数据进行的创新验证的创新方法具有无数的潜在优势，包括更高的生产率，更高的准确性和提高的安全性。此外：

•可以由单个工人进行实施测量。

•一旦捕获数据，就可以测量任意坐标之间的维度或在任何位置查看横截面。

•不再需要拍摄并组织验证照片。

• Being able to calculate XYZ axes deviations is unprecedented and has the potential to increase the precision for maintenance and management.

Even after the construction has progressed and the piles and footings are buried underground and invisible, the status of these invisible structures can be accurately gauged and carefully managed in the future. Keeping a detailed record of the construction process improves safety and reliability and can be expected to reduce the incidence of major accidents.

Moreover, the opportunities for application are likely to expand. Potential uses include uploading the captured data to CIM for processing and combining of the above techniques with VR (virtual reality), AR (augmented reality) and MR (mixed reality) technology, and wearable terminals, changing the nature of construction work.

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Immediately view 3D design data superimposed on point cloud data

Merged as-built point cloud data of the entire structure with 3D design data (CIM).

The ease of use, a familiar operating interface of a total station combined with a high-performance motor drive for high-speed rotation and inversion, and a high laser scanning speed resulted in complete user satisfaction.

“ Nova MS60的最大好处是，您可以实时查看在点云数据上叠加在点云数据上的3D设计数据 - 您只需查看Nova MS60现场的屏幕，然后立即查看差异即可。如果读数不在标准值范围内，则测量位置或其他问题是错误的。因此，通过在工作时检查3D设计数据，您可以验证未造成的算法，没有错误，”explains Kimura.

Kanatsu Giken进行了该试验项目，主题是“充分利用现场技术”，并将工程师和建筑工地汇集在一起​​，以追求创新。

“在这个试验中,我们简单的把提议进行tice, showing that there is an alternative way to do things. As the requirements change due to the shift from engagement to full adoption of i-Construction, we will continue to embrace flexible thinking and creativity to improve productivity on construction sites and make the sites a more attractive place to work,”concludes Kimura.