Rising High with
GPS Network
by Agnes Zeiner Such effects are a particular challenge during the
construction phase of a high-rise building, in as much
The Burj Dubai is the highest-rise building under as the high-rise building under construction is also
construction in the world. When completed in subject to tilt effects and will at least temporarily
2008 it will be the world s tallest building, nearly lose its  usually exactly vertical  alignment.
twice the size of New York s Empire State Build-
ing and higher than the current title holder, the The Burj Dubai in Dubai, UAE, will rise to a height of
Taipei Financial Center (Taipei 101) in Taiwan. The over 800 m when completed in 2008. In addition to
final height is being kept secret. Not a secret on being very tall it is also quite slim and it is anticipated
the other hand, is the unique monitoring system that there will be movement of the building at upper
Leica Geosystems developed together with the levels due to wind loads, crane loads, construction
Chief Surveyor of Burj Dubai. sequence and other factors. The self-climbing form-
work system for the building is complex due to the
In recent years there has been considerable inter- shape of the structure and requires a large number
est in the construction of super high-rise buildings, of control points  currently over 240 are installed.
primarily in the Far East. These buildings are subject
to strong external tilt effects caused, among other Douglas Hayes, Chief Surveyor in Burj Dubai Tower,
things, by wind pressures, unilateral thermal effects and Joel van Cranenbroeck, Business Development
through exposure to sunlight, and unilateral loads. Director at Leica Geosystems, developed a complete-
12 | Reporter
ly new procedure to provide reliable coordinated
points at the top of Burj Dubai using GPS observa-
tions combined with a network of precision inclina-
tion sensors.
At the beginning of construction, six permanent
benchmarks were established and precisely sur-
veyed around the site.  From ground to about Level
20 resection was possible from the external control
marks, which are located about 100 to 150 m from
the base of the tower. Observation redundancy was
possible and very high quality results were achieved ,
says Douglas Hayes. But above Level 20 this system
was not applicable anymore due to obstruction from
the upper decks of the formwork system and poor
visibility.
 The movement of the structure creates several
problems for precise surveys. Theoretically, at any
particular instant in time you need to know exactly
how much the design centre line of the building is
offset from the actual vertical axis and at that same
instant you need to know the precise coordinates of
The  Vertical Cities
the instrument. However, a  mean position for both
elements taken over a short time period can provide
Concept
a suitable solution , says Douglas Hayes. A complex
combination of GPS antenna/receivers, Total Stations,  The challenge taken on by the vertical conquest of
Continuously Operating GPS Reference Stations Leica space is not to beat height records but to redefine
GRX1200 Pro plus Leica GPS Spider and Leica Geo dignified life in large communities. Authentic social
Office Software, together with Leica Nivel220 dual- commitment lies in developing an innovative model
axis precise clinometers, accurately determines and of vertical construction that unites revolutionary
analyzes displacement of the tower alignment from technological concepts capable of exceeding the
the vertical axis. 500 m height limit and the new bio-ecological models
of town planning and architecture in a new philoso-
A dynamic model of the building has been devel- phy of life, say the Spanish architects Javier Pioz and
oped and from this it has been possible to derive Maria Rosa Cervera.
values at any given level for the effect of construc-
tion sequence, building design and solar effects. This Overpopulation, obsolete urban models with all their
 smallest GPS network for the tallest building in the rising problems, and the non-acceptance of the com-
world can be used for tower monitoring both during mon 500 m limit led them to develop their  Verti-
construction and after completion of the structure , cal Cities Concept , based on the consideration that
summarizes Douglas Hayes:  If the Nivel200 Net- nature shows us how to build structures (Bionic Archi-
work is integrated with other monitoring informa- tecture). Their thesis: In massive nuclei and where
tion it will provide a complete system of structural land is scarce  Vertical Cities allow the ecological
monitoring. expansion of cities. For Pioz and Cervera, buildings
up to 1,228 m high (equivalent to 300 floors) with
100,000 inhabitants are the future  for mankind
as well as for the environment:  Nature has all the
answers; in time man will learn all the questions.
The Global Magazine of Leica Geosystems | 13