Topographical/Land Survey (3D)
- 3D Topographical / Land Survey
Sector: Transportation & Infrastructure
About This Project
SurveyWorx were commissioned to manage & deliver the Survey Specification, working in collaboration with the Construction & Design Teams who would lead the Project. The Survey would be completed under strict Traffic Management during normal working hours.
The N2 is a National Primary Road (approximately 145km) connecting Dublin City (M50 Motorway J5) to Northern Ireland (Derry). The N2 Redevelopment Project involved the planning & delivery of a 3D Topographical Survey of approximately 6km of the route.
Survey Methodology & Project Delivery
Using a combination of the latest integrated Robotic Total Stations, GNSS, Digital Levelling & “Robust Survey Methods” to capture & verify accurate Survey Data, the Survey Specification was delivered both efficiently & cost effectively within the strict timescales allocated across the Project.
The Survey Control Network was established using a combination of GNSS, Total Station (1”) & Precise Levelling with Primary Survey Control Stations established every 150m along the route. Topographical Survey Data was captured using a combination of Robotic Total Station (hard standing features) & GNSS (soft standing features).
Establish Control Network Framework
Primary Survey Control (60 Permanent Survey Stations) was established with PK/Mag Survey Nails & Survey Markers drilled/fixed into hard standing surfaces with Station Description Sheets completed for issue to Client/Final Customer. Secondary & Tertiary Control Stations were established when/where required in order to capture data in areas without clear line-of-sight from Primary Control Stations.
Observations/Reading Procedure
Using Leica GNSS Technology 5 Primary Control Stations were Observed/Occupied with Static Observations Logged & Post-Processed in LGO Software.
Traversing (Open Traverse) was completed using a Robotic Total Station (1”), 2 Leica 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) were taken between Primary Control Stations. Angles & Distances were Recorded/Logged in Surveyors 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 information was introduced to the Control Network.
Survey Control Network Post-Processing
Field Observations were Post-Processed through SCC Survey Software to apply Least Squares Adjustment & Scale Factor Corrections with Control Report produced for Analysis & produce final Control Network Coordinates. The Adjusted Network was Transformed to ITM Reference System & Control Station Heights/Z Values were adjusted to include computed precise levelling data.
Adjusted Control Network Report was analysed (Residuals, Standard Errors, Error Ellipses) to validate the final Control Network Coordinates for issue to Client/Final Customer & use across the Project.
Data Acquisition/Capture
Topographical Survey Data was acquired/captured using a combination of Robotic Total Station (hard standing features) & GNSS (soft standing features).
Post-Processing & AutoCAD
Raw Survey Data/Observations were Post-Processed through SCC Survey Software. Data was captured & coded using an SCC Code List ensuring all features were assigned a specific Code when Surveyed & imported on a defined Layering System within SCC. Data was edited within SCC & exported to AutoCAD for further editing & final delivery in accordance with the Project Survey Specification.
Coordinate Reference System
Delivery & Output
The final Drawing Package included; 2D & 3D Topographical Survey, Control Network Report & Control Station Description Sheets. All Drawings were passed through Quality Assurance prior to final delivery.
Topographical Survey Specification
The Topographical Survey would show all features within the Survey Area/Extents. Features shown would include but not be limited to, building outlines, walls, fencing, railings, crash barriers, kerbs, kerb top, drop kerbs, footpaths, road markings, street furniture, all changes of surface, services, with manholes & inspection covers shown with cover level only. All buildings were shown (nearest flank walls only) with levels to ridges & eaves shown, subject to lines-of-sight from the public highway. Spot Levels taken at 10m spacing & at changes of Gradient.
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).
ITM = Irish Transverse Mercator.
Sample Delivery/Output
Services
