Stage 1 is to complete the Bridge Information Review. Information, such as as-built plans, historical inspection reports, and other applicable documents, should be studied in this stage to ensure a complete inspection of the bridge structure. For instance, the review of the inspection reports allows a pilot to identify critical inspection locations (e.g., deck or girders) prior to the drone-enabled inspection. The information gained during this stage permits the pilot to develop flight strategies under limited bridge approachability conditions, identify current damage, and monitor or update critical damage such as concrete cracks on the target bridge.

Stage 2 is to perform a thorough Site Risk Assessment of the bridge’s surrounding areas. This stage is intended to identify potential risks such as near trees or traffic lanes to safely proceed with the drone-enabled inspection. Other benefits of performing a site risk assessment prior to conducting the inspection include identification of safe landing/take off zones, safe bridge approaching areas, and pilot risk minimization. Additionally, state and federal regulations should be accounted for prior to establishing a flying strategy.to ensure pilot safety, traffic control mechanisms, such as warning signs near the pilot, should be implemented.

Stage 3 is to perform the Drone Pre-flight Setup. It is recommended, by both the TC and drone manufacturers, to conduct a thorough inspection of the drone prior to the first flight of the day. Inspections of all the software and hardware including, but not limited to, propellers and rotors, battery levels of all instruments (e.g., a remote controller, storage batteries, and a monitor), remote controller, gimbal, and firmware updates should be conducted. A compass calibration must be performed prior to flying at a new location to prevent GPS signal loss during a flight.

Stage 4 is to complete the Drone-Enabled Bridge Inspection. Once all the preliminary information has been gathered during the previous stages, the inspection using the drone can be conducted. During the operation of the drone, it is necessary to consider weather conditions such as wind, as it can negatively affect the performance of the drone. Aside from weather conditions, the inspection plan should be performed as planned to avoid delays or damage to both the structure and the drone. It is recommended to first capture the overall sections of the bridge and then to gather close-up or detailed information of each structural and non-structural component. It can be noted that current regulation does not allow drone operation over traffic; thus, the inspection of some sections (i.e., with location over roadway) should be conducted from afar.

Finally, per TC regulations, the Pilot-in-Command (PIC) should be continuously assisted by an observer to avoid distractions and possible accidents.

Stage 5 is the most important and to complete the Damage Identification. For a successful drone-based bridge inspection, the damage should be easily identified from the gathered information. The images captured using the drone serve as the basis for further computational analysis including photogrammetry-based inspection. The use of 3D photogrammetric virtual models serves as an overview of the damage compared to conventional 2D images. The reconstruction of 3D virtual models could be completed in a computer software, such as PhotoScan. To construct the 3D virtual model, PhotoScan will need images taken by the drone that can represent points enabling a 3D view of the target structure. Then, using a triangulation technique to connect the points, PhotoScan can generate the surface for a more detailed view and make a texture and color correction. This process is able to provide a visual representation of the target structure in a 3D virtual space.

Culvert Inspection.

Submerged culverts are always challenging in terms of inspection, there are limited head rooms for the inspector to safely complete visual inspection as required by the transportation regulations and law. Therefor inspectors are either required to retain diverse to complete the inspections safely or limit the inspections at the inlet and outlet of the culverts and use engineering judgements to predict the overall condition of the structure. Both approaches are either expensive or not précised and biased based on humans judgement. SMSdrone can safely use remotely controlled robotic machines such as boats or drone in some cases, to inspect the soffit and barrels of the culverts by capturing visible and high resolutions photos and videos with excellent lighting to identify defects such as corrosion , cracks and suspected areas of concrete delamination. These results can be imported to the transportation authorities inspection systems such as BRIDGE MANAGEMENT SYSTEM(BMS)