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是伦敦的第二高建筑。

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.

建造62 storeys, with a floor space of more than120,000平方米必需的Careys土木工程才能倒入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.

这样做Careys和Geosystems的方式

The two core walls of 22 Bishopsgate were constructed 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.

After each jump, or elevation of the rig to build a new level, the Careys Civil Engineering surveying team needed reliable coordinates to proceed setting out the structure and verifying the correct positioning of the core. The main task of the automated positioning system Leica Geosystems created is to obtain precise and reliable coordinates during the entire construction process that are not influenced by the movement of the building.

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
• 倾斜度

与上述硬件和软件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,” said Damien Watson, senior engineer at Careys Civil Engineering, Plant and Fleet department.

为了建立自动定位系统，GNSS站与Leica GeoSystems 360度棱镜相结合，因此，GNSS传感器提供的定位信息可用于用Leica Geosystems进行调查的测量师的参考点机器人总站。bob apple

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.

机器人总站确定了其自身的位置和方向观察控制点，并使用Geomos给出的坐标检查结果。这样，机器人总站观察到在施工期间要检查的所有相关点。

建造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。

“ Leica Geosystems解决方案在需要时自动向测量团队发送参考坐标，并且在每次跳跃后结构都在建筑物增强的建筑物的信心越来越好，”沃森总结。