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The BOW Project
Presented by:
Roger Leeman / MMM Group Limited
The BOW Project – Geodetic Surveying Applied | 2012
The BOW Project
• 58 story (236m) high rise in downtown Calgary
• Once completed will be the tallest building in Western
Canada and future home of the EnCana Corporation.
• ~1.9M ft2 office building
• MMM Responsible for Following Survey Scope:
• Coordinate System
• Project Control Network
• Structural Steel Plumbing and As-builts
• Construction Layout
• Site Survey for +15 Connections
• Real Property Survey
• Strata Subdivision
The BOW Project – Geodetic Surveying Applied | 2012
Horizontal Coordinate System
• Inherited local rectangular system with assumed arbitrary origin
• The local system was represented by a series of wall targets
• Additional levels of control were added and surveyed
• A coordinate transformation was performed to allow for rigorous transformations between local and geodetic systems
• Both local and geodetic coordinates were published for all network stations
• The control network was re-surveyed and re-adjusted on a quarterly basis during the life of the project
• After each re-survey, the network was re-adjusted and any statistically significant coordinate updates were published
The BOW Project – Geodetic Surveying Applied | 2012
Levels of Horizontal Control
• PDC Continuously Operating GPS Reference Stations • Pleiades Data Corp continuously operating GPS Reference Network (2
Stations within 5km)
• Framework Control • Permanent brackets on surrounding stable infrastructure (i.e. bridge
abutments)
• Roof Top Control • Leica 360 Degree Prisms / GPS Antenna mount
• Local Building (Floor) Control • Laser plummet used to plumb horizontal control upward
The BOW Project – Geodetic Surveying Applied | 2012
Vertical Coordinate System
• Local datum had been established
• Local system referenced by wall targets and site benchmark
• Local datum referenced to Calgary ASCM/HPN markers
• A small shift was determined between the local vertical
datum and the ASCM City datum
• Local datum also referenced to Framework Control markers
• The vertical datum was checked to reference benchmarks
on quarterly basis during the life of the project
• Precise steel chains used to extend elevations upward
The BOW Project – Geodetic Surveying Applied | 2012
Project Control Network
The BOW Project – Geodetic Surveying Applied | 2012
• Framework Control • Used to monitor movement of interior roof top prism network.
The BOW Project – Geodetic Surveying Applied | 2012
• Roof Top Control
• 12 roof top control markers
established
• Allowed for observations with
both GPS and Total Stations
• Direct Occupation with Total
Station
• Resection from anywhere on site
The BOW Project – Geodetic Surveying Applied | 2012
Equipment
• Precision Electronic Total Stations
• Leica TS30 – 0.5” angular accuracy / 0.6mm + 1PPM distance accuracy
• Leica TPS1201 – 1” angular accuracy / 1mm + 1.5PPM distance
accuracy
• Robotic and Automatic Target Recognition capability
• On-board least squares resection routine
• GPS
• Leica GPS1230 and Viva systems
• Dual frequency, geodetic quality receivers
• Static accuracy
• 5mm + 0.5 PPM horizontal
• 10mm + 0.5 PPM vertical
• RTK accuracy
• 10mm + 1.0 PPM horizontal
• 20mm + 1.0 PPM vertical
• RTK accuracy increased by averaging observation time over a few
minutes
The BOW Project – Geodetic Surveying Applied | 2012
Equipment
• Spirit Levelling
• Leica DNA03
• Transfer of vertical control
• Rod considerations (go invar!)
• Precise ~0.0003m / turn
• Easy to use and quick
The BOW Project – Geodetic Surveying Applied | 2012
Structural Steel Plumbing / As-builts
• Worked from roof tops of surrounding buildings
• Precise total stations used up to about level 33
• Both direct observation from roof top control markers or resection
techniques used
• GPS techniques used after about level 33
The BOW Project – Geodetic Surveying Applied | 2012
A Dynamic Work Environment
• As the building exceeds a certain cross section to height ratio
building dynamics must be considered and accounted for
• For the Bow, this became significant above level 30.
• Factors affecting building movement
• Wind Loading
• Solar Heating
• Temperature
• Artificial Loading (Cranes/Equipment/People)
The BOW Project – Geodetic Surveying Applied | 2012
Options for Compensating for Building Movement
• Option 1 (Neutral Building)
• Work from on-building locations
• Assume at some point in time the building is in a “neutral” state;
nominally, the early morning hours
• No wind
• No sun
• Stable temperature
• Establish control on the structure when building is in that neutral state
• Very difficult to establish control in stable locations that afforded good
access and visibility
• Option 2 (Monitor and Correct for Building Displacement)
• Work from off-building locations
• Determine building displacement from neutral state and correct for
displacement in near real-time
• For layout survey to proceed, building displacement (deviation from
plumb line) must be compensated for in near real time
• Determine displacement with digital inclinometers
The BOW Project – Geodetic Surveying Applied | 2012
Precision Inclinometer - Leica Nivel 220
• Two-axis high precision inclination sensor
• Optoelectronic data converted to digital output signal
The BOW Project – Geodetic Surveying Applied | 2012
Leica Nivel Inclinometers
• Installed 6 inclinometers (Floors G, 12, 24, 36, 48, 54)
• Measure x inclination, y inclination, time and temperature
• Measures offset in milliradians (mrad) / mm/m
• The height of the Nivel is required in order to determine the
displacement
• Accuracy of .005 mrad
• On-site computer logs data
• Data accessible via Internet remote desktop connection
The BOW Project – Geodetic Surveying Applied | 2012
Inclinometer Tests / Calibrations
• A number of tests were run before inclinometers were used
• Set on tribrach – test x and y movements
• 2 inclinometers on same Column
• 2 inclinometers set on same column (ground and 12)
• Switch inclinometers between ground floor and level 12
• 1 inclinometer set at center of building, 1 inclinometer set near exterior of
building (level 24)
• Calibrate when building in “neutral” state in early morning (1am-6am)
• No solar heating
• Wind minimized
• Loading minimized
• Constant temperature
• Inclinometers were monitored for a minimum of 1 week before they
were brought into service to establish baseline data
The BOW Project – Geodetic Surveying Applied | 2012
Typical Inclinometer Plot – N6
0.500
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1.000
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1.500
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010
12:0
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17/1
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M
Movem
ent
(mra
ds)
X Values
Y Values
The BOW Project – Geodetic Surveying Applied | 2012
Inclinometer / GPS Correction Process
• Structural steel column positioned in approximate position by steel
contractor
• RTK/GPS observations performed on column (nominal 2 minute
observation time)
• Inclinometer data for same 2 minute observation time accessed
• Computer program used to determine building displacement from
neutral state, i.e. plumb line
• Design coordinate of column adjusted to compensate for building
displacement
• Surveyor advises contractor of movement required to position
column in design location
The BOW Project – Geodetic Surveying Applied | 2012
Structural Steel Layout and As-Builts • Tower displacement values derived from inclinometer system used to correct
GPS positions and provide required results.
The BOW Project – Geodetic Surveying Applied | 2012
Column Plumbing-
RTK GPS
• Uses • Layout of Steel Columns
• Advantages/Considerations
• Safety
• Setup considerations
• Base Station Selection
• Urban Canyon L30 and below
• Dynamic structure
The BOW Project – Geodetic Surveying Applied | 2012
Building Floor Control
• Responsible to set control on every floor
• Used by all contractors for layout and as-builting
• 6 horizontal control points established on ground
level and plumbed upwards
• Benchmark set on every floor - elevations extended
upward from ground level
• Set grid lines
The BOW Project – Geodetic Surveying Applied | 2012
Floor Control - Laser Plummets
• Sokkia LV1
• Accuracy +/- 5”
• Range ~100m
• Class 2 Visible beam
• Uses
• Transfer (plumb) horizontal floor
control upward as building grew
• Advantages/Considerations
• Conduits were placed in each floor to
enable plumbing
• Easy to use and quick
• Plexiglass used to catch the beam
• Diameter of the laser beam
The BOW Project – Geodetic Surveying Applied | 2012
Floor Control- Robotic Total
Stations
• Uses
• Floor Control
• Gridline Layout
• Edge of slab layout
• As-builts
• Transfer of Vertical Control
• Advantages/Considerations
• Onboard Resection routine
• Sets of Angles
• Stable floor setups sometimes difficult
The BOW Project – Geodetic Surveying Applied | 2012
Floor Control – Total Stations
The BOW Project – Geodetic Surveying Applied | 2012
Floor Control - Steel Chains
• Uses
• Transfer of vertical control
• Advantages/Considerations
• Requires a precisely calibrated chain
• Requires vertical path to hang freely
• Once setup it becomes very accurate
and fast to transfer elevations.
• Corrections must be applied to
account for:
- Temperature
- Elongation
- Tension
The BOW Project – Geodetic Surveying Applied | 2012
The BOW Project – Geodetic Surveying Applied | 2012
3D Laser Scanning
• Uses
• Accurate as-built of complex features
and connections
• Advantages/Considerations
• Accuracy
• Speed
The BOW Project – Geodetic Surveying Applied | 2012
Scanning Data
The BOW Project – Geodetic Surveying Applied | 2012
Vertigo RTK GPS
The BOW Project – Geodetic Surveying Applied | 2012
Questions