当每毫米计数

作者：Tamas Safar

When thinking of common laser scanning applications, capturing intricate 3D objects or structures comes to mind. Flat, dark surfaces, just like the asphalt of the Zalaegerszeg test track in western Hungary, do not escape, however, the realm of High Definition Surveying (HDS). A 3D smart digital reality of this unique proving ground was created to ensure the track offers driving stability not only for conventional automobiles, but also for autonomous vehicles and electric vehicles.

借助Zalaegerszeg汽车试验场，匈牙利提供了一个无与伦比的场地，标准最高。全球领先的汽车公司，研究团队和大学将在这里从破碎系统，跑步齿轮和轮胎到车载导航系统进行测试；以及在特别城市建造的环境中测试自动驾驶汽车。

来自HírösGeoKFT的HDS专业人员通过分析激光扫描产生的3D点云来评估路面结构和平坦度的质量。

路面点云

Engineering teams need to produce the best possible quality pavement with an even surface so teams can trial automobiles. The dynamic platform is the area of the test track system where the cornering grip/slip friction and overturning stability of the self-driving vehicles incoming at high speed will be tested. Hírös Geo Kft, a Hungarian land surveying, engineering and utility geodesy company, was commissioned for the quality control of the 10 centimetres thick asphalt base layer of the 300-metre diameter circular dynamic platform.

The accuracy requirement was very strict – Hírös Geo Kft needed proof that the top surface of the asphalt base layer deviated only few millimetres relative to the planned plane surface at any of its tested points.

hírös地理kft选择陆地激光扫描以测量沥青偏差。进行测量的专家表明了覆盖动态平台的常规2 cm x 2 cm网格的节点的分歧。所有安装在匈牙利统一国家投影坐标系的测量结果。

Using the Leica ScanStation P40,the detailed survey of the area, consisting of 70,650 square metres, took a full working day。A single setup yielded high-quality data, corresponding to the planned sampling density, within a radius of 40 meters around the laser scanner. 48 setups were collected and linked by using the traverse surveying method. This resulted in a 3D point cloud of about34.5亿度。基本清洁过程之后，在Leica Cyclone寄存器软件中评估了点云。

“It would be impossible to carry out the control measurement with traditional surveying technology. The ScanStation P40 gives us freedom and flexibility to produce the needed amount of data, scaled directly to the project requirements,”HírösGeoKft的Barna Bodri测量专家说。

As flat as a strap

The high-precision registration of the setups was perhaps the biggest challenge. The process could not be assisted by the 3D point cloud post processing software’s recognition of “identical surfaces” (auto-alignment and visual alignment of the point clouds) because the asphalt is a monotonous, flat, dark surface without any points of orientation. Instead, black-and-white targets above the ground control points enabled the registration to be globally准确至1.8毫米。

评估数据明显显示上surface of the asphalt layer has a match of nearly 90 per cent, provided that the deviation of the measured points cannot be greater than a few millimetres to the best fit plane. To lay the asphalt layers, operators relied on the Leica iCON iGG3 to guide the grader with precise control of the blade. Thanks to the 3D coordinates, it was easy to define and stake out in the field which areas need milling before the binding layer was placed. From here, the milling is an easy process using automated iCON machine control.

What caught the eye of experts at the Hungarian civil engineering company in charge of building the automotive proving ground was the presence of indirect signs of strip-like elongations, parallel to the direction of the travel, of the areas outside the specified tolerance exactly where the edges of the asphalt tracks meet. Protruding surfaces are related to the temperature of the asphalt when spread – an asphalt track already laid is in the cooling phase when the connecting strip is deposited at elevated temperatures. The higher the difference in temperature between the joining surfaces, the more difficult it is for the road roller to smoothen the connection.

Creating digital realities

Reality capture allowed HDS experts in Hungary to measure and verify the surface uniformity with a 3D georeferenced model, optimising the construction workflows and digitally sharing information between the field and office.

需要与校正服务进行牢固的沟通，但不能总是依靠。尽管在调查期间，尽管移动网络对卫星的可见性和对该区域的覆盖率不佳，但智能天线的高度敏感板和计算机核心提供了可靠的厘米级定位。特别适合这种较低人口稠密的区域，并具有不稳定的RTK沟通，SmartLink Fill帮助Noviy Proyekt专家提高了专家即使丢失了RTK数据链接，也保留定位精度。

根据提出的有用信息，专家optimised their workflows and reduced the required time and coststo achieve quality work most effectively.