Precise positioning in London’s sky

Author:Renata Barradas Gutiérrez

City landmarks are not built overnight. In between planning, design and construction, there are other crucial activities - just like monitoring and positioning - happening at the same time.

22 Bishopsgate, a287米高的摩天大楼，通过英国伦敦金融区的空中升起。计划以雄心为首都的第一个“垂直村”，22 Bishopsgate是London’s second tallest building。

To construct the cores that make this landmark rise, Careys Civil Engineering, a well-known construction company with a proven track record of delivering projects that enhance the built and natural environments of communities and infrastructure in the United Kingdom and Ireland, delivered the concrete works using a self-erecting jump form system – the first of its kind to be used in the UK.

Building62层, with a floor space of more than120,000 square metres必需的Careys土木工程才能倒入58,000 cubic metres of concreteand use7,500 tonnes of reinforcement。繁荣的复杂和具有挑战性的项目this magnitude requires innovative methodologies

– just like the building positioning system developed for Careys Civil Engineering by Leica Geosystems. This tailor-made solution for jump form high-rise buildings was chosen by Careys Civil Engineering to provide reference coordinates to monitor and carry out the surveying tasks during construction.

这样做Careys和Geosystems的方式

22个主教的两个核心墙是由Careys土木工程制造的，该墙壁工程师使用跳跃形式系统进行了几种混凝土倒入。跳板系统是工作平台或钻机，用于修复模板，钢固定和混凝土。该系统适用于高层结构中多层垂直混凝土元件的构建。

每次跳跃或钻机的高程以建立一个新的水平后，Careys土木工程测量团队需要可靠的坐标来继续设置结构并验证核心的正确定位。自动定位系统Leica Geosystems创建的主要任务是在整个施工过程中获得精确可靠的坐标，而这些坐标不受建筑物的运输影响。

该量身定制的基于GNSS的监视解决方案包括：

• SevenLeica GM30 GNSS receivers for monitoring
• SevenLeica AR10 GNSS antennae
• Leica Geomos显示器
• Leica GNSS蜘蛛软件
• HXGN SmartNet参考站网络
• Tiltmeters

With the above-mentioned hardware and software combination, Leica Geosystems developed a procedure, using GNSS observations combined with tiltmeters (precision inclination sensors), to obtain reliable coordinated points at the top of the formwork of the ascending skyscraper. Those coordinated points, or Active Control Points (ACP), are sighted by Leica Geosystems robotic total stations to setup its coordinates and orientation.

“Above a certain height, in central London, ground control points were not usable or visible anymore; the GNSS system was able to provide reliable coordinates with no need for ground controls,” Careys土木工程，工厂和车队部高级工程师Damien Watson说。

To set up the automated positioning system, GNSS stations were coupled with Leica Geosystems 360-degrees prisms, so the positioning information provided by the GNSS sensors was available to be used as reference points for the surveyors performing the survey of the core wall with Leica Geosystems robotic total stations.

High-precision tiltmeters, fixed at the same locations of the GNSS antennae, were coupled to the GNSS station to track the verticality of the GNSS antennae in order to provide, at each computation, the most accurate coordinates. SmartNet network was used to provide reference coordinates to the GNSS stations on the rigs and compute the baselines.

Ensuring a smooth data flow

为了获得ACP，在专用PC上收集，存储并在使用Spider软件进行后处理数据，以提供团队最准确的坐标。蜘蛛是计算定位信息的控制中心软件。从钻机上的GNSS站的数据和SmartNet参考网络的数据合并，每六个小时为Careys土木工程团队提供每六个小时的最准确的坐标集。将蜘蛛坐标自动转移到Geomos监视器中，在那里它们被转换为局部坐标并根据TILTMETERS数据进行调整。

“Leica Geosystems解决方案允许在需要时进行完全自动化的工作流程和结果计算，并在需要时快速交付坐标，优化调查团队的运营成本和运行时间，与不同的方法相比，沃森说。

The team was, furthermore, able to check the number of satellites tracked and data quality of each single point in the Spider interface in real time. All these quality checks provided in real time the high level of positioning measurement accuracy that Careys Civil Engineering needed to build this landmark.

After each jump and processing period, new valid control points coordinates were available for the robotic total station to measure any mark or object in the structure. The Careys Civil Engineering team on site then proceeded to set up the robotic total station at the top level where all control points were visible.

The robotic total station determined its own position and orientation observing the control points and checking the results with the coordinates given by GeoMoS. In this way, the robotic total station observed all relevant points to be checked during the construction.

Building on the rise

准确且可靠的定位在显示为可行的数据的结构状态，对于做出快速有明智的决策并对潜在问题做出反应至关重要。基于GNSS的监测系统已被证明是如此成功，以至于Careys土木工程将在未来的项目中使用它，例如在曼彻斯特建造新塔楼。

“勒ica Geosystems solution automatically delivered reference coordinates to the surveying team when needed, and the accuracy got better and better while the structure was growing building confidence after every jump,”concluded Watson.