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，通过在英国的伦敦金融区的空中升起。计划与首都第一个“垂直村”，22个突廊的野心是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楼层, with a floor space of more than120,000 square metres要求生涯的土木工程倒58,000 cubic metres of concreteand use7,500 tonnes of reinforcement. Thriving on complex and challenging projects of 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.

做它的生涯'和Geosystems的方式

22金融城的两个核心墙构造ted by Careys Civil Engineering in a sequence of several concrete pours using a jump form system. Jump form systems are working platforms or rigs for fixing of the formwork, steel fixing and concreting. This system is suitable for the construction of multi-storey vertical concrete elements in high-rise structures.

在每次跳跃或钻机的高度建立一个新的水平之后，Careys Chary Changeter测量团队需要可靠的坐标，继续进行结构并验证核心的正确定位。创建的自动定位系统Leica Geosystems的主要任务是在整个施工过程中获得精确且可靠的坐标，这些过程不受建筑物运动的影响。

这种量身定制的基于GNSS的监控解决方案包括：

• SevenLeica GM30 GNSS receivers for monitoring
• SevenLeica AR10 GNSS antennae
• 徕卡地质摩托车显示器
• 徕卡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,“Carey Care Condenting，Plant和Fleet部门的高级工程师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

要获得ACP，请在专用PC上收集，存储和用蜘蛛软件进行处理，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。来自钻机上的GNSS站和来自SmartNet参考网络的数据的数据组合为每六个小时为Carey Cinal Engineering Team的每个点提供最精确的坐标。蜘蛛坐标自动转移到Geomos Monitor，其中它们被转换为本地坐标并根据TILTMETERS数据进行调整。

“Leica Geosystems解决方案允许全自动的工作流程和计算结果，并在需要时，优化测量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

对作为可操作数据显示的结构状态的准确和可靠的定位至关重要，以便快速和明智的决策并对潜在问题作出反应。基于GNSS的监测系统已被证明，Carey Cinal Engineering将在未来的项目中使用它，例如曼彻斯特一座新塔的建设。

“The Leica 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.