Engineering Management, Survey & Engineering Works
- Engineering Management
- Engineering Coordination
- Establish / Verify Site Control
- Setting Out – Gridline Positions
- Setting Out – Transferring Heights / Datums
Sector: Construction & Engineering
About This Project
SurveyWorx were commissioned to manage & deliver the Survey Specification, working in collaboration with the Construction & Design Teams who would lead the Construction/Development of the Project.
The Greenwich Peninsula Project is a mixed-use development in North Greenwich, London, comprising over 500 Apartments/Homes across 7 RC Frame High-Rise Buildings/Structures, ranging from 12 to 32 Floors/Levels.
Scope of Services
Pre-Construction Verification Works
- Verify Control Network & Topographical Survey.
Site Engineering Works
- Establish / Verify Control Network & Site Grid System.
- Setting Out – Pile Locations.
- Transfer Control – Zenith Plummet Vertical Transfer.
- Setting Out – Gridline Positions
- Transfer Datums
- Precise Level
- Suspended Steel Tape (Under Tension).
- Pre-Pour Checks – Slab Edge & Decks.
- Setting Out – MetSec
- QA Sub-Contractors Site Works.
Construction Verification As-Built Survey Specification
- Slab Level Verification (+/- SSL)
- Slab Edge Position
- Columns Position & Verticality
- Structural Beams Position & Level
- Slab Openings/Penetrations
- Lift Shaft Position & Verticality
Survey Methodology & Project Delivery
Control Network Framework
Primary Survey Control Stations were located on Site & Verification/Checks were completed utilising a combination of GNSS, Robotic Total Station (1”) & Precise Levelling Techniques. Verification/Checks would highlight +/-0.004mm in Position & +/-0.007mm in Height. Primary Control was Adjusted & additional Survey Stations were included to determine optimum Network Geometry & ensure adequate Redundancy was present within the Control Network Framework.
Permanent PK/Mag Survey Nails & Survey Markers were drilled/fixed into hard standing surfaces. Photographic Documentation of Survey Stations was captured with Station Descriptions Sheets completed for issue to Client.
Instrument & Prism Station Checks
Checked/Verified the Horizontal Collimation & Vertical Index Errors of Total Station & all Plummets & Bubbles were Checked/Verified to be in Adjustment.
Observations/Reading Procedure
A Closed Loop Traverse was completed using Total Station (1”), 2 No. Prism Stations mounted on Heavy-Duty Tripods with Forced Centring utilised. Cross-Bracing Observations/Readings were taken (when/where possible) to ensure adequate Redundancy was present within the Control Network. 3 Rounds of Angles & Distances (Face Left & Face Right Observations/Readings) taken between Primary Control Stations. Angles were recorded/logged in Field Books to enable additional Verification/Checks. A “double run” levelling loop was completed between all Survey Control Stations using a Leica DNA03 & Invar Staff ensuring accurate Height/Z information was introduced to the Control Network.
Post-Processing & QA
Field Observations/Readings were Post-Processed through MicroSurvey’s STAR*NET Software, with a full Network Adjustment Report produced to highlight Least Square Results. The Adjusted Control Report was analysed (Residuals, Standard Errors, Error Ellipses) to validate final Control Network Coordinates.
Differential Levelling/Precise Levelling
Field Observations/Readings were Post-Processed through SCC Atlas Survey Software to compute final 1D Station Height/Z Values.
Site Engineering Works
Control Transfer – Primary Control (Street Level)
Primary Survey Control was transferred to the Ground Floor of each Block, with Closed Loop Traverse completed. Permanent PK/Mag Nails with Survey Markers were drilled/fixed into Slab for Vertical Control Transfer (GeoFennel FLP-150 Laser Plummet). Photographic Documentation of Survey Stations was captured with Station Description Sheets completed for issue to Client.
Observations/Reading Procedure
Traversing (Closed Loop) was completed using Total Station (1”), 2 No. Prism Stations mounted on Heavy-Duty Tripods with Forced Centring utilised. Cross-Bracing Observations/Readings were taken (when/where possible) to ensure adequate Redundancy was present within the Control Network. 3 Rounds of Angles (Face Left & Face Right Observations/Readings) taken between Primary Control Stations with Angles & Distances Recorded/Logged in Engineers Field Book to enable additional Verification/Checks. A “double run” levelling loop was completed between all Survey Control Stations using a Leica DNA03 & Invar Staff ensuring accurate Height/Z information was introduced to the Control Network.
Post-Processing Field Observations
Field Observations/Readings were Post-Processed through MicroSurvey’s STAR*NET Software, with a full Network Adjustment Report produced to highlight Least Square Results. The Adjusted Control Report was analysed (Residuals, Standard Errors, Error Ellipses) to validate final Control Network Coordinates.
Transferring Levels
Primary Level/Height Control was Transferred to Ground Floor Level on each Block with 1 No. Permanent Brass Bolt drilled/fixed into each Core; Bench Mark (BM) & 1 No. Permanent Brass Bolt was fixed into the Concrete Slab; this Bolt was fixed close to the Core to minimise the effects of deflection.
Transferring the Zenith / Vertical Plumbing Control
The following method was used to Transfer Vertical Control through the High-Rise Structures. In each instance a Minimum of 3 Points was required per Floor/Level.
Instrument: GeoFennel FLP-150 Laser Plummet (Accuracy +/- 2.5mm at 100m)
Set Up over Control Point & Plumb through the Vertical. Check/Verify by Rotating/Spinning the ZNL through 360 Degrees – 90/180/270/0.
Datum – Vertical Transfer
Survey Methodology
Suspended Steel Tape under Tension Method
Level Datums were Transferred to each Level using Suspended Steel Tape under Tension. The process was repeated on a different Core, after shifting the Tape, allowing readings from a different section, thereby minimising the possibility of misreading values.
The Standard Temperature for Steel Tape was 20 Degrees Celsius. Therefore, if the Temperature was significantly different from this value then the appropriate adjustment to the Readings was applied.
Site Datums
Level/Height Datums were established at Finished Floor Level (FFL) +1.000m. Establishing them at FFL +1.0m ensured that they were easy to Install, readily visible and easy to use.
Datums were Marked as SurveyWorx Datums along with Date & Value SW-58.316 – 01/01/20##
Datums were always referenced to Site Bench Mark Transferred at Ground Floor Level. All Height Information was referenced from BM to ensure Settlement did not affect Datums on upper levels as the Buildings/Structures rose.
Weekly Checks/Verification was carried out between the External Primary Control (BM) & Site BM to Monitor Settlement across the Project.
Setting Out Works
Gridline Intersections were Nailed/Pinned to ensure permanent Reference Points would remain on each Slab prior to screeding works. These were Drilled/Fixed using Resin to ensure stability & durability throughout the Project.
QA & Data Validation
We worked closely with our Client during the Pre-Construction Phase to develop & implement Quality Assurance & Data Validation Procedures in relation to Site Engineering/Setting Out Works completed across the Project. All Setting Out Data was extracted from Design Drawings & loaded directly to Instruments.
Setting Out Points were Verified/Checked by Surveying/Recording the Points (from different locations) & overlaying this information on Design Drawings to produce detailed “As-Set Out Drawings” which included Dimensions to highlight any deviation from Design.
Construction Verification & QA
Using HD Laser Scanning Technology & Robotic Total Station (1”) to efficiently capture highly accurate & reliable data, 2D Survey Drawings would be delivered for all Blocks.
Columns, Walls, Slab Levels, Soffit Levels, Lift Shaft Threshold Values, Structural Penetrations, Verticality & Lift Shaft Detail were Surveyed & Presented to highlight any deviations in the actual real-world position of structural elements when compared & analysed against Design Drawings.
Coordinate Reference System
Survey Data related to the OS Network OSGB36(15).
Delivery & Output
Glossary
GNSS = Global Navigation Satellite Systems.
RTK = Real Time Kinematic.
GPS = Global Positioning System.
OSGB36 = Ordnance Survey National Grid Reference System.
ETRS89 = European Terrestrial Reference System.
WGS84 = World Geodetic System (GPS/GNSS).
Sample Delivery/Output
Services
