Precise positioning in London’s sky

Author:Renata BarradasGutiérrez

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-metre-tall skyscraper, rose through the air in London’s financial district in the United Kingdom. Planned with the ambition to be the capital’s first ‘vertical village’, 22 Bishopsgate is伦敦的第二高建筑。

为了构建使这个具有里程碑意义的岩心升高的核心，Careys土木工程工程公司是一家著名的建筑公司，其业务绩效记录，可增强英国和爱尔兰的社区和基础设施的建筑和自然环境，交付了混凝土工程使用自我设计的跳跃形式系统，这是英国使用的第一个。

建造62 storeys，地板空间超过120,000平方米required Careys Civil Engineering to pour58,000立方米的混凝土and 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.

Doing it the Careys’ and Geosystems’ way

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.

This tailor-made GNSS-based monitoring solution consisted of:

• SevenLeica GM30 GNSS接收器用于监视
• SevenLeica AR10 GNSS天线
• Leica GeoMoS Monitor
• Leica GNSS Spider software
• HXGN SmartNetreference station network
• 倾斜度

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,” 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。亚博5分钟快三

高精度倾斜仪,固定在同一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

To obtain the ACP, data was collected, stored and post processed with Spider Software at a dedicated PC to deliver the most accurate coordinates for the team. Spider is the control centre software where positioning information was computed. The data from the GNSS stations on the rig and data from the SmartNet Reference Network was combined to provide every six hours the most accurate set of coordinates for each point for Careys Civil Engineering team. Spider coordinates were automatically transferred to GeoMoS Monitor where they were transformed into local coordinates and adjusted based on tiltmeters data.

“徕卡呈规则允许对一个完全的解决方案automated workflow and computation of the results and fast delivery of coordinates when required, optimising costs and time of operation for the surveying team compared to different methodologies,” said Watson.

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

Accurate and reliable positioning on the status of structures displayed as actionable data is crucial to make fast and informed decisions and react to potential problems. The GNSS-based monitoring system has proven so successful that Careys Civil Engineering will be using it in future projects, such as the construction of a new tower in Manchester.

“ 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立建筑物的信心越来越好，”沃森总结。