We were recently commissioned to inspect the 1000 square metre roof of an industrial unit in Hoddesdon, Hertfordshire. The imagery was required to support a condition report which had been commissioned by the potential new owner of the unit, as they wanted to know the state of the building before handing over their money! 
 
Our client was structural engineering firm Bond Davidson, and we worked closely with one of their structural engineers to make sure all areas of interest were captured in the survey — these were primarily the condition of the bolts fixing the roof panels in place, the general condition of the roof panels themselves, the condition of the gutters and the condition of the roof around any protrusions through the roof's surface, eg. chimneys. 
Drone aerial inspection photo of the roof of an industrial unit in Hoddesden, Hertfordshire
We were recently commissioned to inspect the 1000 square metre roof of an industrial unit in Hoddesdon, Hertfordshire. The imagery was required to support a condition report which had been commissioned by the potential new owner of the unit, as they wanted to know the state of the building before handing over their money! 
 
Our client was structural engineering firm Bond Davidson, and we worked closely with one of their structural engineers to make sure all areas of interest were captured in the survey — these were primarily the condition of the: 
 
Bolts fixing the roof panels in place 
Roof panels themselves 
Gutters 
Roof around any protrusions through the roof's surface, eg. chimneys. 
 
The first type of imagery we capture during an inspection shoot like this is 4K stabilised video. This gives a quick overview of what the structure looks like, and allows the entire structure to be examined without having to flick through multiple images. The video below shows a single pass along one of the roof surfaces — this same process was then repeated for the other roof surfaces until the entire structure had been inspected. 
 
Click on the play button below to watch the video. 
Short 4K stabilised video of a roof inspection in Hoddesdon, Hertfordshire. This video complemented the high-resolution still photographs that were taken at the same time. Click the play button to watch the video and be sure to click the rectangle icon in the bottom right to watch the video full-screen, and the gear symbol to select '2160p' for the video quality. 
Whilst each frame of this 4K video has a resolution of just over 8 megapixels, the still photographs that we took separately have a resolution of 20 megapixels, making them much more suitable for fine examination of the building's structure. 
 
Below are a handful of the 32 photographs that were taken during the shoot — click any image to enlarge it. 
Drone aerial inspection photo of the roof of an industrial unit in Hoddesden, Hertfordshire
Drone aerial inspection photo of the roof of an industrial unit in Hoddesden, Hertfordshire
Drone aerial inspection photo of the roof of an industrial unit in Hoddesden, Hertfordshire
Drone aerial inspection photo of the roof of an industrial unit in Hoddesden, Hertfordshire
A selection of drone aerial inspection photographs of the roof of an industrial unit in Hoddesdon, Hertfordshire, taken to support a pre-purchase condition report. Click to enlarge. 
As mentioned previously, the camera on our drone has a resolution of 20 megapixels which allows photographs to be enlarged on a computer with very little loss of detail. The images below show how far you can zoom into one of the inspection photographs without losing detail — the image on the left is straight from the camera (with some minor post-processing to enhance the shadow detail) and the image on the right shows a 100% crop from the same image, showing how closely the images can be scrutinised. 
Drone aerial inspection photo of the roof of an industrial unit in Hoddesden, Hertfordshire
100% crop from a drone aerial inspection photo of the roof of an industrial unit in Hoddesden, Hertfordshire
An overall image (LEFT) and a 100% crop from the same image (RIGHT) showing the level of detail provided by our drone camera. Click to enlarge. 
Need even more detail? There are two options: 
 
Fly closer to the subject in question! 
Fit a longer focal-length lens. We currently use three lenses — a wide-angle lens (mainly used for architectural marketing images), a mid-length telephoto lens (suitable for the majority of inspection work) and a long telephoto lens (ideal for situations where the drone has to maintain a safe distance from the object being inspected, or when very high levels of detail area required). 
 
This particular shoot was complicated by the presence of a main road within 30 metres of one side of the building. Whilst it was safe to hover the drone high above the building as this kept the straight-line distance between the road and the drone above the legal 50m limit for commercial drone operations, this meant that we couldn't get any close-up details of the gutters along one side of the building as it would have meant flying too close to the road. 
 
The solution? Our 50-foot telescopic mast of course! We put the mast up in a couple of locations along the side of the building closest to the road and were able to quickly check the condition of the gutters — quite full as it turned out as you can see in the images below!  
Mast aerial inspection photo of the roof of an industrial unit in Hoddesden, Hertfordshire
Mast aerial inspection photo of the roof of an industrial unit in Hoddesden, Hertfordshire
Some of the mast aerial inspection photographs of the roof of an industrial unit in Hoddesdon, Hertfordshire, taken to support a pre-purchase condition report. Our drone couldn't be used on this side of the building due to its proximity to a nearby main road. Click to enlarge. 
In total we spent about 1.5 hours on the site taking the aerial photographs of the 1000 square metre roof structure. Normally a survey of this scale could have been completed within an hour, but this site required use of both the telescopic mast and drone due to the building's proximity to the nearby main road. 
 
Our client was delighted with the service we provided — particularly how we had all the equipment required to perform a complete inspection of this building's roof, regardless of its proximity to nearby roads. They recently sent us the kind testimonial below: 
"We needed photographs at height to support a commercial building survey. David had a great range of kit including drone, poles, and high quality camera equipment. He was prompt and professional, and enabled us to successfully advise our client on the roof problems that were not visible from the ground." 
Do you work for a chartered surveyors or structural engineering firm? Do you wish there was a way of getting high-resolution preliminary photographs of awkward-to-access roofs or other high-level structures without having to use a cherry picker, abseilers or erecting scaffolding? Give us a call today for a chat about our aerial inspection services — it's likely to be quicker and more cost effective than you might imagine! 
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