Ontario Line First Order Control

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Industry

Pre-Engineering

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Type

Engineering Surveys

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The Challenge

Multiple Ontario Line contracts create risks of coordinate misalignment at interface points. Metrolinx required a high-accuracy control network for the Lakeshore East Joint Corridor to ensure consistency and reliable project alignment.

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The Solution

IBW established a 22-station high-precision control network by verifying existing monuments and adding new ones, creating a reliable reference for all survey and construction work.

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The Result

The network met and exceeded Metrolinx standards for Survey Control in Transit Corridor, which has a requirement of 1 cm local accuracy and 2 cm network accuracy, ensuring precise alignment across Ontario Line segments.

Project summary

Primary Geodetic Control Network for the Ontario Line – Lakeshore East Joint Corridor

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Toronto, ON

IBW Surveyors Ltd. was retained by Metrolinx to establish a primary geodetic control network for the Lakeshore East Joint Corridor segment of the Ontario Line.

The objective of this work was to create a high-accuracy survey framework that would serve as the foundation for all survey, engineering, construction layout, and monitoring activities within this portion of the corridor.

Equally important, the network was designed to ensure precise alignment with adjacent Ontario Line construction contracts, providing a consistent reference system across project limits and supporting seamless integration of infrastructure built under separate contract packages.

Primary Geodetic Control Network - IBW Surveyors

Technical Details

Control Network Establishment Methodology

To achieve first-order survey accuracy, IBW implemented a dual methodology combining GNSS observations with high-precision terrestrial measurements.

Vertical Control

Digital leveling observations were performed between benchmarks using forward and backward loops to verify the vertical control network and ensure closures remained well within allowable tolerances.

Horizontal Control

Static GNSS observations were collected at control stations to establish reliable baselines. These observations were supplemented with a high-precision terrestrial traverse to strengthen network geometry and provide redundancy across the corridor.

Network Adjustment

All observations were processed and rigorously adjusted using least-squares adjustment techniques to confirm network stability and verify compliance with Metrolinx accuracy standards.

Ontario Line First Order Control | IBW Surveyors

Equipment & Technology

High-Precision Survey Instruments & Processing

To achieve the precision required for a primary transit control network, IBW deployed high-accuracy geodetic survey equipment including:

GNSS Receivers

Trimble R10 and Trimble R12i GNSS receivers were used for static baseline observations, collecting dual-frequency carrier phase measurements to establish high-accuracy horizontal control.

Total Stations

A Trimble S9 HP 0.5″ robotic total station was used for high-precision terrestrial traversing and control densification. Observations were performed using forced centering techniques and precision prism targets to minimize setup error.

Digital Leveling Equipment

Leica DNA03 digital levels paired with Invar precision staves were used to establish and verify vertical control tied to the project datum.

Processing Software

Survey observations were processed and adjusted using:

Trimble Business Center for GNSS processing and data management
MicroSurvey StarNet for rigorous least-squares network adjustment and statistical validation