Facade Inspections using Drones - Key Considerations
Updated: Nov 4, 2022
Facade Inspections have always been a bit difficult. Especially in the case of a tall structure or building, it can be hard to get the scaffolding up and perform the inspection in a safe and efficient manner.
Drones have changed the game. Not only can you reach hard-to-access areas in a fraction of the time, you can also record and capture high resolution images of the building facade. These images can be later used analyse the facade's condition collaboratively in an office environment.
So how do you exactly perform these inspections and what are the things to watch out for?
Let's take a look.
Start with the End Goal
With any inspection, it's important to have an end goal in mind. Is the inspection data going to be reviewed by a surveyor or a building manager? What would they be looking for? Is it cracks, defects or water leaks? Knowing what the end customer or stakeholder is looking for will help you design your unique way of performing the inspection with the drone and capture the best possible data.
Facade Inspections, unlike other drone missions, represent a number of key challenges.
Let's have a look at them one by one.
1. GPS Availability
If you're planning to inspect a building in a congested area, one of the first things to understand is if your drone would have good GPS signal during flight. Buildings can block GPS signals. Having GPS signal strength would mean a more stable flight and will allow you to use automation to collect data with higher levels of precision.
If you believe GPS is going to be an issue, try to understand if you can change the takeoff location or fly your drone to a high enough altitude first for it acquire good GPS strength.
Should GPS positioning fail, you should be ready to take over ATTI (non-GPS) control over the drone at any point.
2. Number of Facades
Another important thing to consider is the number of facades you plan to capture with your drone and therefore the flight path the drone would have to take.
If you plan to capture a single facade of a tall building, it's more optimal to fly up and down the building to cover its longest side first. On the other hand, if you plan to capture multiple facades of a relatively short building, it's better to fly left-right first and then top to bottom.
Being able to maintain line of sight is critical here and you might have to split your flight plan into multiple flights - one for each facade.
Understand the height of the building and the number of facades to be inspected.
3. Takeoff Locations
As you perform your flight's risk assessment, it is often useful to consider where to takeoff the drone from. Looking at the site on Google Maps / Earth ahead of time will give you an idea of where to takeoff your drone from. If feasible, you should also consider visiting the site ahead of time to perform a site survey. One option could be to takeoff from the roof the building. With this approach, it is important to consider the impact on the drone's relative altitude. Most drones use a barometric sensor for altitude estimation and estimate their altitude relative to the takeoff location. So if you're planning to takeoff from the roof to inspect a facade, you'll notice your drone report negative altitudes during flight.
We hope this list gives you a sense of some of things to look at for while planning facade inspections. Let's now take a look at mission planning and how to capture high-precision inspection data!
If you have flown photogrammetry missions before, the mission planning should come naturally to you. Essentially, mission planning & automation for facade inspections is akin to nadir / orthophoto missions but flipped in the vertical plane.
1. Estimating the height of the building
Performing an automated facade inspection begins with being able to accurately determine the height of the building. We recommend using the drone as a measurement tool here and fly it to the top and the bottom of the building to capture the true height of the building, as per the drone's reported altitude. We make this process super simple with altitude fetchers in Hammer. With altitude fetchers, you can manually fly your drone to the top of the building, press a single button and record the height of the building. You can then repeat the same process to capture the bottom of the building.
Altitude Fetchers in Hammer - fly your drone to the building top and tap to capture the altitude!
2. Camera Type, Overlap and Horizontal Distance
The second challenge in mission planning is to be able to determine the distance you should fly from the building to capture the images at the desired overlap. Obviously, the camera you are using also plays a role in this as every camera would have a different field of view. Once again, we've made this process super simple for you in Hammer. Simply select the horizontal distance you wish to keep from the building, your desired overlap (we recommend 20% for inspections, 70%+ for photogrammetry) and your camera type, and Hammer will calculate the most optimal positions to take the photos in flight.
Setup your camera type, overlap and horizontal distance to the facade
Once you've planned your mission, you can simulate your flight in Hammer to understand what you would expect on the field. One of the common challenges with these inspections is making sure that the planned images are crystal clear and devoid of any motion-blur / focus issues. Hammer can also automate this process for you. Simply toggle on the focus-before-pictures switch and Hammer will focus the drone's camera before every picture.
Share in 3D with Other Stakeholders
Congratulations! You're now aware of the common challenges in facade inspections using drones and how to combat them.
We recognise that conducting these inspections is typically a team effort, so once you've created your mission plan, you can share this with your team and other stakeholders in the project, by exporting the mission to KML format in Hammer. This KML file can then be rendered on Google Earth on top of the building's 3D model (if available) in Google Earth. Visualising the plan on Google Earth allows you to gain critical feedback from other stakeholders in the project, and once again ensure that you collect the best data possible once you're on site.
Sharing your planned facade inspection mission with other stakeholders.
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 firstname.lastname@example.org.
Learn more about our post processing options here
We hope this guide provided you with an insight into some of the operational challenges while conducting a facade inspection using drones. Every facade 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 platform 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 or get started with our web platform here.
To learn how to use Hammer for facade inspections, please visit our tutorial on facade 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 email@example.com.
We look forward to hearing from you.
- The Hammer Team