unpiloted systems
With the rapid growth of the drone industry, the interest from construc - tion, engineering, real estate, and insurance communities in using UAS for building, roof, and infrastructure inspections is observed globally. This can range from inspecting buildings, bridges, chimneys, open pit walls, dams to communications and electrical infrastructure like cell towers or wind turbines. Traditionally these types of inspections are performed by highly trained inspectors using rope or scaffolding, mak - ing them more dangerous and thus driving up the cost. Fully automated drone vertical inspections are not only safer, they also allow for more precise data collection, which is very important for post-processing. Automating vertical inspections in North America Many cities in the United States are mandating building facade inspec - tion programs to proactively identify any unsafe conditions that could pose a risk of injury or damage to property. For example, in the city of Chicago, all buildings with a height of at least 80 feet need to be inspected every 4 to 12 years based on the category of the building. Noticeably, it is possible for stakeholders to perform these surveys us - ing drones without getting a waiver from the Federal Aviation Admin - istration (FAA). Moreover, with the nationwide deployment of Low Altitude Authorization and Notification Capability (LAANC) and the 14 CFR Part 107 by the FAA, it is now possible to obtain approval to perform drone inspections of these objects even when there are multi - ple airports or helipads around. (Barnhart, Marshall & Shappee, 2021) In Canada, dam inspections with the use of a UAV are an extremely innovative area where there hasn't been a lot of growth. For detailed crack mapping and inspections, the traditional method is to send teams of engineers out on the structure, sometimes using rope ac - cess, where they have a harness, and they climb down the structure and manually measure each crack and then map each of them out with pen and structural drawings. A UAV method of data collection Drones automate vertical inspections, increase employee safety By Alexey Dobrovolskiy
is more efficient, much safer for the team, and creates a digital model that can then be referenced over time which is extremely important. For example, a Canadian trend setter in UAV-based dam inspections, Niricson, uses drones because the method allows them to capture high resolution imagery and build a 3D model of the structure that they can now reference for future inspections. The company, in particular, opted for vertical scanning with a UAV in a Colorado project. They wanted to make sure that they maintained a consistent ground sam - pling distance, or basically, a consistent pixel size for the images, and the approach allowed them to quantify those cracks. Furthermore, they managed this to be repeatable in future surveys to compare how the structure would be changing. Advantages of performing automated vertical inspections compared to manual drone inspection flights Performing vertical drone surveys over manual surveys could be considered advantageous thanks to higher accuracy, repeatability of flights, increased crew safety, and lower costs. The result of vertical scanning surveys with a UAV is a set of images captured with a specific forward and side overlap, which can then be stitched together into a vertical orthomosaic or even a 3D model. This information can then be used to detect defects such as cracks or other damage. For example, in case of building inspection, this can more accurately estimate facade renovation costs and, after the repairs are finished –to check the quality of work of contractors. Performing these types of inspection flights manually would be a dif - ficult task for even the most experienced UAV pilots. This is the reason why most professional surveyors are moving towards automating it with the use of a flight planning software. Since drone surveys are repeatable with a high degree of accuracy, a software may allow the creation of a digital model of the structure after each survey flight, giving the ability to compare multiple models over time to see how the structure is changing to, for example, monitor if any cracks are developing over time. According to Mark Patrick Collins, Associate Professor, Unmanned Systems, from Indiana State University, UgCS, mission planning and flight control software by SPH Engineering, was confirmed to be ap - plicable for building and roof inspections. UgCS allowed users of a focus group to create a façade flight plan vertically across each facade of the building to perform this type of inspection safely and accurately. Users could set the distances from the building and the overlap and UgCS automatically calculates the optimal flight path for the vertical grid pattern. (Barnhart, Marshall & Shappee, 2021) Workflow of planning vertical inspections using drones Performing vertical inspections with drones can be divided into three phases – flight planning, execution, and post-processing. Flight planning is started by drawing polylines on the map around the object. Next, the distance to the object is measured in the software and entered in the parameters. Similarly, the type of camera used and over - lap parameters are entered by the operator along with minimum and maximum altitude values. Two inspection directions can be selected –
Arch Dam 3D Model on AUTOSPEX Platform © Niricson
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