How to do a Roof Inspection using a Drone?

Updated: May 25



Overview


Roof inspections have always been a bit tedious and more than a little dangerous. You have to climb up on a high roof with significant angles that may have a variety of different levels. Then, you walk along, look for damage, and try not to fall.


Fortunately, today’s technology has changed the way roof inspections are done. Now you can use a drone with a camera to safely inspect even the largest and highest roofs.


How? There are many details to it. In this post, we'll cover 7 operational challenges that you might encounter during roof inspections and how to combat them.


Know What You’re Looking For


Roof inspections are all about collecting quality data that can be processed later into meaningful insights. Make sure you know what you're looking for as it will help you plan your flight. Are you looking for peeling shingles, cracks, water leaks or damage?


A residential inspection for a roofing company will have different needs to an architectural

assessment ahead of a renovation. Whether you’re a service provider or part of an in-house drone team, it pays to know exactly what data you're planning to capture during the flight!


7 Operational Challenges while inspecting a Roof


1. Small vs Large Roof


When you start off with a roof survey, it's important to consider the size and height of the roof. Is it small roof that you can capture by flying manually or is it a large roof (e.g. retail, supermarkets, warehouses etc) where you might need to fly this mission automated. Flying with automation allows you to capture consistent data all over the large roof and capture 5x faster.


With smaller roofs, It's typically easier to maintain line-of-sight during flight. In the case of a large roof, maintaining line-of-sight of the drone is obviously harder. We recommend studying the roof on Google Maps and working out the best locations for takeoff that allow for good line-of-sight of the drone. You might have to split your flight plan into smaller parts and fly them separately to achieve this.


2. Visual and Thermal Surveys


Does this roof inspection require visual data only? Or does it require thermal data as well? For a thermal survey, you will require a thermal camera such as the Zenmuse XT. The challenge is that thermal inspections are only effective when the sun is low in the sky to avoid sun's heat interfering with the roof's inherent thermal signature. On the other hand, the visual survey will require good lighting conditions. So do you fly the visual and thermal inspections at different times in the same day? How do you ensure that the visual and thermal datasets align with each other in post processing is also an important consideration.


3. Focus issues during capture


During a visual inspection, it's common to experience the camera losing focus. This can happen if the drone began its mission with the camera facing the sky or a distant object and since then it has switched to look at the roof. Since this is an inspection mission, it is important for every picture to be razor sharp so that you or your client can zoom into the photos without losing detail.


Fortunately, this is something Hammer, our flight software, can help with. Simply create your roof inspection mission and toggle on the 'Focus Before Picture' option.


Unfocussed Roof Image (Blurry)


Focused Roof Image (Sharp) Image credit: Ocuair


4. Offset from the Ground


Another commonly experienced challenge is the offset from the ground, which affects the overlap in your captured pictures. Typically, most flight planning software calculate the overlap in flight from the specified altitude with respect to the ground. However, as you might imagine, in a roof inspection, the drone is flying above a roof and therefore the camera's footprint on the roof (as opposed to the ground) is different. This is where being able to set the ground offset comes in handy. In Hammer's roof inspection mission, this option is built-in so that you can simply set the ground offset to the height of the building and let Hammer take care of the rest.



Ground Offset During Roof Inspections



Ground Offset is closely related to overlap. It's important to cross-check the overlap you are expected to get in your inspection, and therefore we've built in a simple way in Hammer for you to check the expected overlap. Simply tap on the picture points in the Roof Inspection mission and you can visualise the image overlap on the map.


Camera footprint, visualised on the map.



5. 'L' shaped roofs


'Large L' shaped roofs can be particularly tricky. If you come across an L shaped roof, and try to capture it automatically, most flight planning software will lead to over-flying (flying over the grid as opposed to the 'L)'. This leads to excessive flying and we know how important drone battery life is. Once again, this is not an issue with Hammer's roof inspection mission as it is purpose built for this task.


L shaped Roof Inspection in Hammer



6. Oblique view to see the surface


In any good inspection, it's important to maximise the areas that can be seen and captured by the sensor. For a roof survey, it's important to be able to get not just the top-down (nadir) view of the roof, but also the oblique view to inspect any vertical assets and installations on the roof. We recommend using the 'Gimbal Pitch' setting available in flight planning software to get an oblique view of the roof as well. This setting for DJI drones is -90' degrees for a top-down view and -70' degrees for an oblique view.


7. Orientation for Post Processing


Last, but not the least, it's important to ensure that your drone maintains a constant orientation during the flight. This is not strictly necessary, but if the goal is inspection, you probably don't want to be changing the orientation of the photos every time the drone starts a new flight line. It's difficult for humans to look through the dataset later and make sense of it if the orientation changes all the time. This is why Hammer includes an option to make the drone maintain constant orientation throughout the roof inspection mission.


Post Processing


Once you've collected the data, we recommend using a data inspection platform to sift through the images and annotate your findings. You can even run your data through AI-based defect detection software to speed up your analysis process. If you'd like to learn more about data processing options, please feel free to get in touch with us at team@hammermissions.com.




Summary


We hope this guide provided you with an insight into some of the operational challenges while conducting a roof inspection using drones. Every roof inspection is slightly different, so don't be afraid to add your own creativity to the data capture process!


At Hammer, we provide an extremely adaptive flight planning app for commercial drones, that helps you capture the best data possible for your specific needs. If you'd like to try Hammer, feel free to download the app through the App store.


To learn how to use Hammer for roof inspections, please visit our tutorial on roof inspections using Hammer.

If you're interested to learn more about our enterprise solutions, including mission collaboration, flight analytics and more please contact us at team@hammermissions.com.


We look forward to hearing from you.


- The Hammer Team

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