Controlling Verticality of High-Rise Buildings Using GNSS Techniques Integrated with Laser Plummet

Maintaining vertical alignment is crucial in the construction of high-rise buildings (HRBs). Traditionally, construction teams use laser plummets to transfer reference point coordinates from the foundation to each floor through openings in the concrete slabs. However, as building height increases, the accuracy of the laser beam can be affected, necessitating verification. In an urban development project in Al Alamein, Egypt, the use of the Global Navigation Satellite System (GNSS) was proposed to monitor verticality during construction. For the 270-meter-tall T-TOWER, nine monitoring points were established on the foundation to define the building’s axes for each slab. These points were transferred to subsequent floors using a laser plummet and verified with a static GNSS system. A geoid model and an Earth gravity field model were employed to align the GNSS-recorded coordinates with the laser plummet datum by calculating vertical deflections.Verticality monitoring for T-TOWER was conducted from the 6th to the 67th floor, at intervals of six floors. Results indicated that the deviation between GNSS and laser plummet coordinates was ±0.5 cm for the first 100 meters, increasing to ±2 cm at 270 meters. After correcting for vertical deflections, the deviation was reduced to less than ±1.9 cm. The static GNSS system proved effective for monitoring verticality in HRB construction, maintaining coordinate deviations within a few millimeters for heights up to 100 meters. For heights beyond 100 meters, correcting vertical deflections helps minimize deviations. The measurement deviations remained within the design requirements of ±3.0 cm for HRB structures up to 400 meters. This approach offers a more accurate and reliable method for monitoring vertical alignment, reducing structural errors in high-rise buildings, especially in modern urban projects like New Alamein City