Drone Surveying & Reality Modeling

Safer, Faster, Efficient, Innovative

MMC Gamuda, turnkey contractor for Malaysia’s metro megaproject MRT SSP Line, are managing the construction of 13.5km of twin bored tunnels and 17 individual construction sites of various sizes (largest exceeding 17000 sqm) situated in dense urban areas of Kuala Lumpur, Malaysia. With an undertaking of such enormity, quick, accurate, safe surveying is key to the successful delivery of the project. Our surveyors and engineers are capitalizing on the ability of drones to acquire large volumes of data with extraordinary speed, which can then be processed and shared on the cloud for multiple BIM & GIS uses and used for regular site progress reporting.

Our survey and engineering teams make extensive use of Bentley Systems ContextCapture reality modeling software to generate a digital twin of each of our sites. https://www.bentley.com/en/products/brands/contextcapture

Application of drone data capture and reality meshes

Thanks to the high precision, acute mobility, phenomenal speed and relatively low cost of data capture achievable, the use of drones along our 13.5 km and 17 construction sites has brought about numerous unexpected and previously unavailable benefits. The Effective drone uses for the project include:

Reinventing Surveying

Surveying takes an average of two man hours of drone flight and approximately a half-day of post processing per site. By comparison, a traditional survey would take 200 man hours to complete with limited data collected. We use a photogrammetry process in ContextCapture which converts hundreds of overlapping images captured by drones to a reality mesh of the site to develop a digital twin.

The survey data and reality meshes are made available to all of the project teams via a common data environment in various formats to enable interoperability across cloud-based BIM and GIS data platforms.

As the models are accurate and reliable, they can be used to quickly measure distances, areas and volumes, saving enormous amounts of effort for surveyors and engineers.

Integrating with BIM

Our original intent to survey sites by drones was to create a reference model for review and validation with BIM design data. The drone survey models provide realistic accurate digital representation of each site which enhances communication across the project (between sites, project offices, consultants and client). We successfully developed a workflow which integrates 3D photorealistic meshes into our federated BIM design models, greatly enhancing constructability and design review processes. The integration of drone models with BIM have dramatically enhanced our designer’s understanding of site constraints and context.

Leveraging GIS to improve access to Digital Twins

Photographs from the drone surveys are processed to generate accurate ortho-mosaic images for mapping and GIS applications. We identified an opportunity to grant all project members quick and convenient access to our site survey models via our project GIS platform. This has strengthened and informed our decision-making processes by visualising these sites in their localities and having a virtual bird’s eye view over them, giving us context and a sense of proportionality.

People based overseas are ble to review site activities virtually and identify potential construction or temporary works related issues in a timely manner via these systems. Delivering the ContextCapture models online using the GIS platform has democratized access to site surveys and enabled our teams to have regular visibility of our sites without the need for extensive site visits.

Enhancing Health & Safety

Drones allow remote monitoring of construction sites. Following an incident on one of the station box excavations, drones were deployed to survey the site and assess risks of further collapse without endangering any workers. We are now exploring additional potential uses of drones to reduce risk in difficult to access or dangerous locations. Drone data will also be used with AI for virtual health and safety inspections and future training.

Video Explanation

Watch our video to see how drone surveys have become an integral component of our site surveying, data collection and progress reporting. The photogrammetrically derived meshes from Bentley ContextCapture enable us to keep our client and stakeholders informed in meaningful ways which were previously impossible without drones.

Planning & Executing Drone Surveys

The following key points should always be considered when using drones for data collection;

+ Each flight must be pre-planned to ensure successful image & data capture for ortho-mosaics, photogrammetry reality meshes and for progress reporting.

+ All drone flight operations shall be pre-approved and sanctioned by JUPEM and CAAM, the regulatory agencies for Malaysia. Prior to each flight, the drone pilot notifies the local air traffic controllers using the permit NOTAM reference.

+ Each flight should be controlled using drone operations planning software to set the flight path, elevation and speed of the drone.

+ Drones typically operate between 70m and 100m above the site.

+ A dedicated take-off & landing zone must be clearly marked and located at least 30m away from any active working areas. 

+ During flight operations, a spotter must monitor the drone, the surrounding air space and maintain radio comm’s with the pilot and site safety manager at all times.

+ Ground Control Points are essential to accurately position the data collected by the drones in relation to the project grids and local or national coordinate system. As the surveys are highly accurate and precisely located by GCP to the project grids, the permanent works can be reliably measured and quantified.

+ Ortho photos created from the drone surveys can be used in GIS to accurately plot construction activities on site.

+ Reality meshes derived from photogrammetry enable site progress reporting and can also be analyzed and reviewed over the project cycle for progress monitoring.

+ A reality model of each site can be compared to the design BIM data to review actual progress compared to planned works.

+ The survey model can be compared to the BIM system. In this example the structural walls which were cast are checked for alignment.

+ Measurement. The survey models are accurate enough for distance measurement which saves the engineers time. The 3D surface models can be used to quickly measure cut & fill volumes and these are more accurate and faster than traditional 2D processes.

All of the data collected by the drones (Orthomosaics, 3D models, photos & video) are shared online via a GIS interface within an internet browser.

Winners - Bentley Systems Year In Infrastructure 2019 Awards

MMC Gamuda's comprehensive, innovative programme for reality modeling of a complex urban tunnel system set a new standard for quick, accurate and safe surveying. The team are advancing the state-of-the-art use of drones in construction through a growing list of uses, from tracking construction progress over time, to comparing as-built conditions against BIM data, to estimating excavation quantities and to assessing unsafe areas.

Finalist Judges

Watch my recent webinar Presentation on drone applications here