当每个毫米计数

Author:塔玛斯·萨法尔（Tamas Safar）

当考虑常见的激光扫描应用时，就会想到捕获复杂的3D对象或结构。但是，像匈牙利西部的Zalaegerszeg测试轨道的沥青一样，并不能逃脱高清测量的领域（HDS）。创建了这一独特的证明地面的3D智能数字现实，以确保赛道不仅为传统汽车，而且为自动驾驶汽车和电动汽车提供驾驶稳定性。

With the Zalaegerszeg Automotive Proving Ground, Hungary provides an unparalleled venue with the highest standards. The world’s leading automotive companies, research teams and universities, will test here from breaking systems, running gears and tires to onboard navigation systems; as well as testing self-driving vehicles in an especially urban-built environment.

HDS professionals from Hírös Geo Kft assessed the quality of the pavement structure and flatness by analysing 3D point clouds generated by laser scanning.

Point clouds for pavement

工程团队需要用均匀的表面生产最佳的质量路面，以便团队可以试用汽车。动态平台是测试轨道系统的区域，将测试高速驾驶车辆的转弯握把/滑动摩擦和自动驾驶车辆的稳定性。匈牙利土地测量，工程和实用工具公司HírösGeoKft因其300米直径直径圆形动态平台的10厘米厚沥青底层的质量控制而受到委托。

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 Geo Kft chose terrestrial laser scanning to measure the asphalt deviation. The specialists carrying out the measurement presented the divergences from the measured surface in the nodes of a regular 2 cm x 2 cm grid covering the dynamic platform. All measurements fitted to the Hungarian Unified National Projection measuring coordinate system.

使用Leica扫描仪P40，该地区的详细调查，包括70,650平方米，度过了整个工作日。单个设置产生的高质量数据，与计划的采样密度相对应，在激光扫描仪周围40米的半径内。使用Traverse测量方法收集了48个设置并链接。这导致了大约3D点云34.5亿个度量。Point clouds were evaluated in the Leica Cyclone REGISTER software after a basic cleaning process.

“通过传统的测量技术进行控制测量是不可能的。ScanStation P40为我们提供了自由和灵活性，可以直接缩放到项目需求，以生成所需的数据数量，”said Barna Bodri surveying specialist at Hírös Geo Kft.

像皮带一样平坦

设置的高精度注册也许是最大的挑战。由于沥青是单调的，平坦的，黑暗的表面而没有任何方向，因此无法通过3D点云后处理软件对“相同表面”（自动对准和视觉对齐）的识别而无法帮助该过程。相反，地面控制点上方的黑白目标使注册在全球范围内准确至1.8毫米。

评估的数据清楚地表明，沥青层的上表面的匹配近90％，前提是测得的点的偏差不能大于最佳拟合平面的几毫米。要铺设沥青层，操作员依靠Leica图标IGG3来指导叶片的精确控制。多亏了3D坐标，在放置绑定层之前，很容易在现场定义和固定哪个区域需要进行铣削。从这里开始，使用自动图标机控制是一个简单的过程。

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.

创建数字现实

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.

Based on the presented useful information, expertsoptimised their workflows and reduced the required time and costs最有效地实现高质量的工作。