The integration of UAV (Unmanned Aerial Vehicle) technology and aerial photogrammetry has redefined the standards for monitoring, designing, and maintaining critical assets. We support engineering companies to survey, monitor and verify projects, combining the accuracy of traditional topography by GPS and total station with the convenience of aerial photogrammetry by drone.
Among the strategic advantages of drone-based infrastructure mapping there is the possibility to capture data from angles that are impossible to reach via ground-based equipment and with minimized operations disruption.
Drones make it affordable to perform weekly or even daily scans of a construction site to track progress against CAD designs and by utilizing RTK (Real-Time Kinematic) drones and Ground Control Points (GCPs), we deliver centimeter-level accuracy essential for structural analysis.
Large Dams and Hydraulic Works
Beyond the initial survey, drones are essential for post-construction monitoring. In such high-stakes environments, periodic photogrammetric analysis allows for the detection of micro-displacements or structural anomalies invisible to the human eye, which could lead to catastrophic results.
If necessary, we could even integrate sonar/bathymetric surveys to map the underwater basin and create a complete 3D model of the reservoir capacity.
Case Study:
Client: Major international EPC contractor
Scope: Performing survey works to determine boundary conditions, confirm existing controls and elevations, determine all existing surface features, and identify and develop site contour mapping for the construction of a dam in the Kingdom of Saudi Arabia.
In addition to the topographic survey, our teams have been conducting monthly aerial missions to monitor site conditions.
Results: Technometer has contributed to one of the region’s most complex giga-project environments with over 5,000,000 m2 of surveyed and monitored areas, more than 10,000,000 m³ of verified earthworks and volumetric reconciliations, and 100+ km of control networks and alignment verification implemented.
In mountainous dam sites, drones capture the vertical rock faces where a human cannot stand, while ground teams establish a high-precision geodetic network at the base to ensure the entire 3D model is perfectly oriented to the national grid.
To provide appropriate georeferencing for aerial photogrammetric surveys, our teams have installed approximately 40 Ground Control Points (GCPs), marked indicators on the ground with known coordinates, strategically positioned in the surveyed area and clearly visible by the drone camera.
The ground position accuracy of the GCPs was 0.02 m (1-σ) in each horizontal direction (i.e., latitude and longitude) and 0.03 m (1-σ) in the vertical direction.
The ground survey has been performed using a dual Real-Time Kinematic (RTK) Differential Global Positioning System (DGPS) to enable high-quality data collection for georeferencing and mapping purposes, ensuring centimetre-level accuracy in horizontal and vertical measurements.
The base instrument evaluates the GPS signal errors by comparison between the estimated position and the known (true) position; the evaluated error is then sent in form of differential corrections to the rover, which applies the corrections on the measured position in order to obtain a better coordinates estimation.
The differential corrections can be applied either in real time, through a radio link between the base and the rover GPS (generating the RTK, Real Time Kinematic, operation mode) or with the base and rover instruments individually recording the GPS signals while keeping their position for a certain period (static mode) and then by post processing the differential corrections stored in the base.
The topographical data taken by the drone, comprising a large number of high-resolution images, were processed using photogrammetric technique.
This methodology involves acquiring images of the same area from various perspectives, with partial overlapping.
Through the identification of common points in multiple images and considering parameters such as camera position, camera orientation, focal length, lens distortion, etc. it is possible to calculate the spatial location of each point in a three-dimensional space (triangulation process).
When a single point is identified in two images (minimum) taken from distinct known locations, it is possible to visualize imaginary lines extending from the two camera positions toward that specific point.
Subsequently, using dedicated algorithms, the intersection of these lines can be calculated, providing the XYZ coordinates of each point.
A comprehensive 3D digital elevation model of the surveyed area is obtained by repeating this process for the thousands of common points identified in the images collected by the drone.
The aerial images collected during the surveys were subsequently processed utilizing Agisoft Metashape, in order to generate, among various outputs, a digital Elevation model (DEM) and an orthophoto for each captured scenario.
The methodology used includes the following main steps:
- UAV Imagery Alignment
- Ground Control Points
- Alignment Optimization
- Point Cloud
- Digital Elevation Model
- Orthomosaic
- Contours Generation
Other uses that drones can have in the infrastructure sector:
- Bridge and Viaduct Inspections:
Traditional bridge inspections often require scaffolding, snooper trucks, or industrial climbers, while with drones we can use high-resolution cameras to capture 4K imagery and 3D models of piers, abutments, and underside decks, or identify hairline fractures or concrete carbonation on a highway overpass in hours rather than days, significantly reducing inspection costs and safety risks.
With our hybrid approach we can use a drone to inspect the underside of a deck – or any other areas inaccessible to humans – while ground teams use laser scanners or total stations to ensure the bridge’s vertical alignment remains within safety tolerances: drones capture the overall geometry and surface condition (cracks, spalling), while traditional topography provides fixed monitoring points on piers and abutments to track seasonal expansion or structural “creep” with sub-millimeter precision.
- Roadway and Highway Expansion:
We can generate massive orthomosaic maps and contour maps to assist in volume calculations for earthworks, ensuring that soil transport logistics are optimized and budget overruns are avoided.
Also, by overlaying drone orthomosaics on top of ground-surveyed benchmarks, we can identify exactly which sections of a highway are prone to water pooling (hydroplaning risk) through highly accurate drainage slope analysis.
- Railway Corridor Management
Railways are linear assets that are notoriously difficult to survey as they require a balance of “macro” monitoring for vegetation and “micro” monitoring for track or pavement integrity.
With our drones, automated flight paths allow us to map hundreds of kilometers of track, identifying rail wear, ballast condition, and vegetation encroachment.