Innovating as-built verification

Author: Yoshie Katagiri

In 2018, the Japanese Ministry of Land, 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.’

The objective of the four-company consortium was to conduct 3D laser scanning on concrete structures, such as bridge abutments and piers, and use the acquired point cloud data for as-built verification to dramatically improve the productivity of construction sites. In addition, they trialled and proposed a new method of progress management using the differences between the captured point cloud data and the coordinate values of the 3D design data (CIM).

Kanatsu Giken使用了Leica GeosystemsLeica Nova MS60 MultiStation, an instrument capable of 3D laser scanning with the surveying functions of a conventional total station.

“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,”描述了Kanatsu Giken土木工程部信息技术小组的团队负责人Yoshinobu Kimura。

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)

Planar (roughness) comparative evaluation of point cloud data obtained by measuring the as-built of cast-in-place piles against 3D design data

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

平面（粗糙度）通过测量与3D设计数据的基础构建获得的点云数据的比较评估

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.

With the trial techniques, one person can operate the Nova MS60 to perform measurement and photography.The trial techniques reduced the number of man-hours required for measurements of cast-in-place piles by more than half.

基础是具有减震功能的钢筋混凝土基础。倒角时，读取准确的角点可能是一个问题。

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测量工作减半

In the case of piers, due to the requirement to take measurements at height and in confined spaces, planar evaluations using 3D point cloud data is very useful.

该试验是在日本Ohguni高架桥外部和下部的两个桥梁基台上和两个桥梁的施工过程中进行的测量和验证。试验的结果分为现场桩，基础和住房。

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.

“With the conventional method, when we measured the standard height of the top of the pile, we used a stepladder or something similar to climb over the reinforcements that protrude from the pile and had a surveyor stand in the centre. The pile diameters were measured by teams of two, taking measurements in two directions - one along the axis of the bridge, and the other, perpendicular to this. This work was repeated again and again until all the piles were measured. Another worker was needed to take photos of the as-built verification process.

Nova MS60,你可以测量从外面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,”Kimura解释。

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.

此外，由于将NOVA MS60捕获的数据上传到点云处理系统以进行临时测量，因此无需单独拍摄照片以进行验证。这也消除了在现场工作后组织照片所涉及的时间。

The footing is a foundation of reinforced concrete placed on top of the cast-in-place piles. In the trial, the scaffolding proved to be an obstacle. The piers sit on the footing and support the bridging superstructure.

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.

通过测量码头的完成形状和设计数据（蓝线）获得的点云数据的比较

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

“对于基础和码头，我们只管理了约20％的货运量。但是，如果有许多结构要测量，即使20％也代表了一个大量节省。同样，如果建立3D激光扫描作为标准过程，则建筑工地将设计工作流以建造和去除脚手架，以便可以有效地进行测量，这应该会进一步减少量子。”木村说。

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

This innovative method of as-built verification using point cloud data has a myriad of potential benefits, including higher productivity, higher accuracy, and improved safety. Furthermore:

• As-built measurement can be performed by a single worker.

• Once the data has been captured, it is possible to measure dimensions between arbitrary coordinates or view cross sections at any position.

• It is no longer necessary to take and organise as-built verification photos.

•能够计算XYZ轴的偏差是前所未有的，并且有可能提高维护和管理的精度。

即使在建设进行了，桩和基础也被埋葬在地下和看不见的情况下，这些无形结构的状态也可以在将来准确地测量和仔细管理。保持施工过程的详细记录可提高安全性和可靠性，并有望减少重大事故的发生率。

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.

“The greatest benefit of the Nova MS60 is that you can view 3D design data superimposed on point cloud data in real time – you simply look at the screen on the Nova MS60 on-site and see the differences immediately. If a reading is not within the standard value range, either the measurement position or something else is wrong. And so, by checking against the 3D design data as you work, you can verify the as-built without mistakes,”Kimura解释。

Kanatsu Giken conducted this trial project with the theme to ‘Make the most of technology in the field’ and brought together engineers and the construction site in pursuit of innovation.

“在这项审判中，我们只是将提案付诸实践，表明还有另一种做事的方法。随着由于从参与到全面采用I构建的转变而导致的需求变化，我们将继续采用灵活的思维和创造力，以提高建筑工地的生产力，并使站点成为更具吸引力的工作场所，”concludes Kimura.